2025
|
Kovács, A.; Weber, J. T.; Charilaou, M.; Kong, D.; Prodan, L.; Tsurkan, V.; Schröder, A.; Kiselev, N. S.; Kézsmárki, I.; Dunin-Borkowski, R. E.; Tavabi, A. H.; Schäfer, S. All-optical stochastic switching of magnetisation textures in Fe3Sn2 Journal Article Commun. Mater. 6, 223 (2025). @article{kovacs_all-optical_2025,
title = {All-optical stochastic switching of magnetisation textures in Fe_{3}Sn_{2}},
author = {A. Kovács and J. T. Weber and M. Charilaou and D. Kong and L. Prodan and V. Tsurkan and A. Schröder and N. S. Kiselev and I. Kézsmárki and R. E. Dunin-Borkowski and A. H. Tavabi and S. Schäfer},
url = {https://doi.org/10.1038/s43246-025-00974-1},
doi = {10.1038/s43246-025-00974-1},
year = {2025},
date = {2025-10-14},
urldate = {2025-10-01},
journal = {Commun. Mater.},
volume = {6},
number = {1},
pages = {223},
abstract = {The all-optical control of magnetisation at room temperature broadens the scope of applications of spin degrees-of-freedom in data storage, spintronics, and quantum computing. Topological magnetic spin structures, such as skyrmions, are of particular interest due to their particle-like properties, small size and inherent stability. Controlling skyrmion states without strong magnetic fields or large current densities would create new possibilities for their application. In this work, we utilize femtosecond optical pulses to alter the helicity of the spin configuration in dipolar skyrmions formed in the kagome magnet Fe3Sn2 in the absence of an external magnetic field and at room temperature. In situ Lorentz transmission electron microscopy is used to visualise the light-induced stochastic switching process of chiral Néel caps, while the internal Bloch component of the dipolar skyrmions remains unchanged. In addition to this switching process, we observe the interconversion between type I skyrmionic and type II bubble configurations depending on the external magnetic field and illumination conditions. To corroborate the spin states and the light-induced magnetisation dynamics, micromagnetic modelling and simulations of the resulting electron phase shift maps are conducted to elucidate the spin rearrangement induced by individual femtosecond optical pulses.},
keywords = {C2},
pubstate = {published},
tppubtype = {article}
}
The all-optical control of magnetisation at room temperature broadens the scope of applications of spin degrees-of-freedom in data storage, spintronics, and quantum computing. Topological magnetic spin structures, such as skyrmions, are of particular interest due to their particle-like properties, small size and inherent stability. Controlling skyrmion states without strong magnetic fields or large current densities would create new possibilities for their application. In this work, we utilize femtosecond optical pulses to alter the helicity of the spin configuration in dipolar skyrmions formed in the kagome magnet Fe3Sn2 in the absence of an external magnetic field and at room temperature. In situ Lorentz transmission electron microscopy is used to visualise the light-induced stochastic switching process of chiral Néel caps, while the internal Bloch component of the dipolar skyrmions remains unchanged. In addition to this switching process, we observe the interconversion between type I skyrmionic and type II bubble configurations depending on the external magnetic field and illumination conditions. To corroborate the spin states and the light-induced magnetisation dynamics, micromagnetic modelling and simulations of the resulting electron phase shift maps are conducted to elucidate the spin rearrangement induced by individual femtosecond optical pulses. |  |
Rao, P.; Knolle, J. Order-by-disorder in magnets with frustrated spin interactions—classical and large-S limits via the spin functional integral Journal Article J. Phys.: Condens. Matter 37, 405802 (2025). @article{rao_order-by-disorder_2025,
title = {Order-by-disorder in magnets with frustrated spin interactions—classical and large-S limits via the spin functional integral},
author = {P. Rao and J. Knolle},
url = {https://doi.org/10.1088/1361-648X/ae0bdf},
doi = {10.1088/1361-648X/ae0bdf},
year = {2025},
date = {2025-10-07},
urldate = {2025-10-01},
journal = {J. Phys.: Condens. Matter},
volume = {37},
number = {40},
pages = {405802},
abstract = {We investigate spin systems with extensive degeneracies in the classical ground states due to anisotropic frustrated spin interactions, where the degeneracy is not protected by symmetry. Using spin functional integration, we study the lifting of the degeneracies by fluctuations called order-by-disorder (ObD), and the associated gap in the spin-wave spectrum. It is shown that ObD corresponds to gradient-dependent anisotropic interactions of the pseudo-Goldstone modes, which vanish for a classical uniform spin configuration. Fluctuations generate a gradient-independent effective potential which determines the ground state and the pseudo-Goldstone gap. Furthermore, we recover previous predictions for the pseudo-Goldstone gap in type-I and II ObD with two-spin interactions in the large spin-S limit or the classical small temperature limit, by computing the gap explicitly for the type-II cubic compass model and the type-I square compass model. We show that these two limits correspond to the one-loop approximation for the effective potential. We also discuss other types of order by disorder due to m-spin interactions where m > 2.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
We investigate spin systems with extensive degeneracies in the classical ground states due to anisotropic frustrated spin interactions, where the degeneracy is not protected by symmetry. Using spin functional integration, we study the lifting of the degeneracies by fluctuations called order-by-disorder (ObD), and the associated gap in the spin-wave spectrum. It is shown that ObD corresponds to gradient-dependent anisotropic interactions of the pseudo-Goldstone modes, which vanish for a classical uniform spin configuration. Fluctuations generate a gradient-independent effective potential which determines the ground state and the pseudo-Goldstone gap. Furthermore, we recover previous predictions for the pseudo-Goldstone gap in type-I and II ObD with two-spin interactions in the large spin-S limit or the classical small temperature limit, by computing the gap explicitly for the type-II cubic compass model and the type-I square compass model. We show that these two limits correspond to the one-loop approximation for the effective potential. We also discuss other types of order by disorder due to m-spin interactions where m > 2. |  |
Heinsdorf, N.; Joshi, D. G.; Katsura, H.; Schnyder, A. P. Fate of Bosonic Topological Edge Modes in the Presence of Many-Body Interactions Journal Article Phys. Rev. Lett. 135, 146702 (2025). @article{heinsdorf_fate_2025,
title = {Fate of Bosonic Topological Edge Modes in the Presence of Many-Body Interactions},
author = {N. Heinsdorf and D. G. Joshi and H. Katsura and A. P. Schnyder},
url = {https://link.aps.org/doi/10.1103/1pty-fvpf},
doi = {10.1103/1pty-fvpf},
year = {2025},
date = {2025-10-03},
urldate = {2025-10-01},
journal = {Phys. Rev. Lett.},
volume = {135},
number = {14},
pages = {146702},
abstract = {Many magnetic materials are predicted to exhibit bosonic topological edge modes in their excitation spectra, because of the nontrivial topology of their magnon, triplon, or other quasiparticle band structures. However, there is a discrepancy between theory prediction and experimental observation, which suggests some underlying mechanism that intrinsically suppresses the expected experimental signatures, like the thermal Hall current. Many-body interactions that are not accounted for in the noninteracting quasiparticle picture are most often identified as the reason for the absence of the topological edge modes. Here we report persistent bosonic edge modes at the boundaries of a ladder quantum paramagnet with gapped triplon excitations in the presence of the full many-body interaction. We use tensor network methods to resolve topological edge modes in the time-dependent spin-spin correlations and the dynamical structure factor, which is directly accessible experimentally. We further show that signatures of these edge modes survive even when the noninteracting quasiparticle theory breaks down; we discuss the topological phase diagram of the model, demonstrate the fractionalization of its low-lying excitations, and propose potential material candidates.},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
Many magnetic materials are predicted to exhibit bosonic topological edge modes in their excitation spectra, because of the nontrivial topology of their magnon, triplon, or other quasiparticle band structures. However, there is a discrepancy between theory prediction and experimental observation, which suggests some underlying mechanism that intrinsically suppresses the expected experimental signatures, like the thermal Hall current. Many-body interactions that are not accounted for in the noninteracting quasiparticle picture are most often identified as the reason for the absence of the topological edge modes. Here we report persistent bosonic edge modes at the boundaries of a ladder quantum paramagnet with gapped triplon excitations in the presence of the full many-body interaction. We use tensor network methods to resolve topological edge modes in the time-dependent spin-spin correlations and the dynamical structure factor, which is directly accessible experimentally. We further show that signatures of these edge modes survive even when the noninteracting quasiparticle theory breaks down; we discuss the topological phase diagram of the model, demonstrate the fractionalization of its low-lying excitations, and propose potential material candidates. |  |
Ginga, V. A.; Shen, B.; Uykur, E.; Giordano, N.; Gegenwart, P.; Tsirlin, A. A. Pressure-tuned spin chains in brochantite, Cu4SO4(OH)6 Journal Article Phys. Rev. Mater. 9, 094412 (2025). @article{ginga_pressure-tuned_2025,
title = {Pressure-tuned spin chains in brochantite, Cu_{4}SO_{4}(OH)_{6}},
author = {V. A. Ginga and B. Shen and E. Uykur and N. Giordano and P. Gegenwart and A. A. Tsirlin},
url = {https://link.aps.org/doi/10.1103/g459-sxb7},
doi = {10.1103/g459-sxb7},
year = {2025},
date = {2025-09-24},
urldate = {2025-09-01},
journal = {Phys. Rev. Mater.},
volume = {9},
number = {9},
pages = {094412},
abstract = {Using high-pressure single-crystal x-ray diffraction combined with thermodynamic measurements and density-functional calculations, we uncover the microscopic magnetic model of the mineral brochantite, Cu4SO4(OH)6, and its evolution upon compression. The formation of antiferromagnetic spin chains with the effective intrachain coupling of 𝐽≃100K is attributed to the occurrence of longer Cu–Cu distances and larger Cu–O–Cu bond angles between the structural chains within the layers of the brochantite structure. These zigzag spin chains are additionally stabilized by ferromagnetic couplings 𝐽2 between second neighbors and moderately frustrated by several antiferromagnetic couplings that manifest themselves in the reduced Néel temperature of the material. Pressure tuning of the brochantite structure keeps its monoclinic symmetry unchanged and leads to the growth of antiferromagnetic 𝐽 with the rate of 3.2 K/GPa, although this trend is primarily caused by the enhanced ferromagnetic couplings 𝐽2. Our results show that the nature of magnetic couplings in brochantite and in other layered Cu2+ minerals is controlled by the size of the lattice translation along their structural chains and by the extent of the layer buckling.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
Using high-pressure single-crystal x-ray diffraction combined with thermodynamic measurements and density-functional calculations, we uncover the microscopic magnetic model of the mineral brochantite, Cu4SO4(OH)6, and its evolution upon compression. The formation of antiferromagnetic spin chains with the effective intrachain coupling of 𝐽≃100K is attributed to the occurrence of longer Cu–Cu distances and larger Cu–O–Cu bond angles between the structural chains within the layers of the brochantite structure. These zigzag spin chains are additionally stabilized by ferromagnetic couplings 𝐽2 between second neighbors and moderately frustrated by several antiferromagnetic couplings that manifest themselves in the reduced Néel temperature of the material. Pressure tuning of the brochantite structure keeps its monoclinic symmetry unchanged and leads to the growth of antiferromagnetic 𝐽 with the rate of 3.2 K/GPa, although this trend is primarily caused by the enhanced ferromagnetic couplings 𝐽2. Our results show that the nature of magnetic couplings in brochantite and in other layered Cu2+ minerals is controlled by the size of the lattice translation along their structural chains and by the extent of the layer buckling. | |
Ghara, S.; Winkler, M.; Schmid, S. W.; Prodan, L.; Geirhos, K.; Tsurkan, V.; Ge, Wenbo; Wu, Weida; Halbritter, A.; Krohns, S.; Kézsmárki, I. Nonvolatile electric control of antiferromagnetic states on nanosecond timescales Journal Article Phys. Rev. Lett. 135, 126704 (2025). @article{ghara_nonvolatile_2025,
title = {Nonvolatile electric control of antiferromagnetic states on nanosecond timescales},
author = {S. Ghara and M. Winkler and S. W. Schmid and L. Prodan and K. Geirhos and V. Tsurkan and Wenbo Ge and Weida Wu and A. Halbritter and S. Krohns and I. Kézsmárki},
url = {https://link.aps.org/doi/10.1103/yzrk-h3rz},
doi = {10.1103/yzrk-h3rz},
year = {2025},
date = {2025-09-18},
urldate = {2025-09-01},
journal = {Phys. Rev. Lett.},
volume = {135},
number = {12},
pages = {126704},
abstract = {Electrical manipulation of antiferromagnetic (AFM) states, a cornerstone of AFM spintronics, is a great challenge, requiring novel material platforms. Here we report the full control over AFM states by voltage pulses in the insulating Co3O4 spinel well below its Néel temperature. We show that the strong linear magnetoelectric effect is fully governed by the orientation of the Néel vector. As a unique feature of Co3O4, the magnetoelectric energy can easily overcome the weak magnetocrystalline anisotropy; thus, the Néel vector can be manipulated on demand, either rotated smoothly or reversed suddenly, by combined electric and magnetic fields. We achieve the nonvolatile switching within a few tens of nanoseconds between time-reversed AFM states in macroscopic volumes by voltage pulses. These observations render quasicubic antiferromagnets, like Co3O4, an ideal platform for the ultrafast (picosecond to nanosecond) manipulation of microscopic AFM domains and may pave the way for the realization of AFM spintronic devices.},
keywords = {A4, C2},
pubstate = {published},
tppubtype = {article}
}
Electrical manipulation of antiferromagnetic (AFM) states, a cornerstone of AFM spintronics, is a great challenge, requiring novel material platforms. Here we report the full control over AFM states by voltage pulses in the insulating Co3O4 spinel well below its Néel temperature. We show that the strong linear magnetoelectric effect is fully governed by the orientation of the Néel vector. As a unique feature of Co3O4, the magnetoelectric energy can easily overcome the weak magnetocrystalline anisotropy; thus, the Néel vector can be manipulated on demand, either rotated smoothly or reversed suddenly, by combined electric and magnetic fields. We achieve the nonvolatile switching within a few tens of nanoseconds between time-reversed AFM states in macroscopic volumes by voltage pulses. These observations render quasicubic antiferromagnets, like Co3O4, an ideal platform for the ultrafast (picosecond to nanosecond) manipulation of microscopic AFM domains and may pave the way for the realization of AFM spintronic devices. |  |
Wang, Z.; Cui, X.; Treu, T.; Guo, J.; Liu, X.; Klinger, M.; Heil, C.; Ma, N.; Sheng, X.; Deng, Z.; Lu, X.; Wang, X.; Li, W.; Gegenwart, P.; Jin, C.; Zhao, K. Antiferromagnetic ordering and critical behavior induced giant magnetocaloric effect in distorted kagome lattice Gd3BWO9 Journal Article Phys. Rev. Mater. 9, 094407 (2025). @article{wang_antiferromagnetic_2025,
title = {Antiferromagnetic ordering and critical behavior induced giant magnetocaloric effect in distorted kagome lattice Gd_{3}BWO_{9}},
author = {Z. Wang and X. Cui and T. Treu and J. Guo and X. Liu and M. Klinger and C. Heil and N. Ma and X. Sheng and Z. Deng and X. Lu and X. Wang and W. Li and P. Gegenwart and C. Jin and K. Zhao},
url = {https://link.aps.org/doi/10.1103/7l6y-hdw5},
doi = {10.1103/7l6y-hdw5},
year = {2025},
date = {2025-09-16},
urldate = {2025-09-01},
journal = {Phys. Rev. Mater.},
volume = {9},
number = {9},
pages = {094407},
keywords = {B3},
pubstate = {published},
tppubtype = {article}
}
| |
Neehus, A.; Pollmann, F.; Knolle, J. Genuine Topological Anderson Insulator from Impurity Induced Chirality Reversal Journal Article Phys. Rev. Lett. 135, 126604 (2025). @article{neehus_genuine_2025,
title = {Genuine Topological Anderson Insulator from Impurity Induced Chirality Reversal},
author = {A. Neehus and F. Pollmann and J. Knolle},
url = {https://link.aps.org/doi/10.1103/7p8y-2mp6},
doi = {10.1103/7p8y-2mp6},
year = {2025},
date = {2025-09-16},
urldate = {2025-09-01},
journal = {Phys. Rev. Lett.},
volume = {135},
number = {12},
pages = {126604},
abstract = {We investigate a model of Dirac fermions with mass impurities that open a global topological gap even in the dilute limit. Surprisingly, we find that the chirality of this mass term, i.e., the sign of the Chern number, can be reversed by tuning the magnitude of the single-impurity scattering. Consequently, the disorder induces a phase disconnected from the simple clean limit of the topological insulator, which is achieved via an impurity resonance inducing additional bands with Chern number 2. Thus, we call this impurity induced phase a genuine topological Anderson insulator. In seeming contradiction to the expectation that mass disorder is an irrelevant perturbation to the Dirac semimetal, the tricritical point separating these two Chern insulating phases and a thermal metal phase is located at zero impurity density and connected to the appearance of a zero energy bound state in the continuum that corresponds to a perfectly resonant mass impurity. Our conclusions based on the 𝑇
-matrix expansion are substantiated by large scale Chebyshev-polynomial Green’s function numerics. We discuss possible experimental platforms.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We investigate a model of Dirac fermions with mass impurities that open a global topological gap even in the dilute limit. Surprisingly, we find that the chirality of this mass term, i.e., the sign of the Chern number, can be reversed by tuning the magnitude of the single-impurity scattering. Consequently, the disorder induces a phase disconnected from the simple clean limit of the topological insulator, which is achieved via an impurity resonance inducing additional bands with Chern number 2. Thus, we call this impurity induced phase a genuine topological Anderson insulator. In seeming contradiction to the expectation that mass disorder is an irrelevant perturbation to the Dirac semimetal, the tricritical point separating these two Chern insulating phases and a thermal metal phase is located at zero impurity density and connected to the appearance of a zero energy bound state in the continuum that corresponds to a perfectly resonant mass impurity. Our conclusions based on the 𝑇
-matrix expansion are substantiated by large scale Chebyshev-polynomial Green’s function numerics. We discuss possible experimental platforms. | |
Ferreira-Carvalho, M. M.; Rößler, S.; Chang, C. F.; Hu, Z.; Valvidares, S. M.; Gargiani, P.; Haverkort, M. W.; Mukharjee, P. K.; Gegenwart, P.; Tsirlin, A. A.; Tjeng, L. H. Trigonal distortion in the Kitaev candidate honeycomb magnet BaCo2(AsO4)2 Journal Article Phys. Rev. B 112, 125135 (2025). @article{ferreira-carvalho_trigonal_2025,
title = {Trigonal distortion in the Kitaev candidate honeycomb magnet BaCo_{2}(AsO_{4})_{2}},
author = {M. M. Ferreira-Carvalho and S. Rößler and C. F. Chang and Z. Hu and S. M. Valvidares and P. Gargiani and M. W. Haverkort and P. K. Mukharjee and P. Gegenwart and A. A. Tsirlin and L. H. Tjeng},
url = {https://link.aps.org/doi/10.1103/2sdd-pyx1},
doi = {10.1103/2sdd-pyx1},
year = {2025},
date = {2025-09-16},
urldate = {2025-09-01},
journal = {Phys. Rev. B},
volume = {112},
number = {12},
pages = {125135},
abstract = {We conducted x-ray absorption (XAS) and magnetic circular dichroism (XMCD) measurements at the Co 𝐿2,3 edges on single crystals of the Kitaev candidate honeycomb lattice compound BaCo2(AsO4)2. The measurements employed the inverse partial fluorescence yield technique, which is ideal for acquiring reliable x-ray absorption spectra from highly insulating samples, enabling precise quantitative analysis. Our experimental results revealed a significant linear dichroic signal, indicating strong trigonal distortion in the CoO6 octahedra in BaCo2(AsO4)2. We performed a detailed analysis of the experimental XAS and XMCD spectra using a full-multiplet configuration-interaction cluster model. This analysis unveiled that the 𝑡2𝑔 hole density is predominantly localized in the 𝑎1𝑔 orbital. Through XMCD sum rules and theoretical calculations, we quantified both the spin and orbital magnetic moments. Our study demonstrates that the local electronic structure of the CoO6 octahedra displays an effective trigonal distortion of approximately −0.114 eV. This distortion is larger than the Co 3𝑑 spin-orbit coupling constant, emphasizing the crucial impact of local structural distortions on the electronic and magnetic properties of BaCo2(AsO4)2.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
We conducted x-ray absorption (XAS) and magnetic circular dichroism (XMCD) measurements at the Co 𝐿2,3 edges on single crystals of the Kitaev candidate honeycomb lattice compound BaCo2(AsO4)2. The measurements employed the inverse partial fluorescence yield technique, which is ideal for acquiring reliable x-ray absorption spectra from highly insulating samples, enabling precise quantitative analysis. Our experimental results revealed a significant linear dichroic signal, indicating strong trigonal distortion in the CoO6 octahedra in BaCo2(AsO4)2. We performed a detailed analysis of the experimental XAS and XMCD spectra using a full-multiplet configuration-interaction cluster model. This analysis unveiled that the 𝑡2𝑔 hole density is predominantly localized in the 𝑎1𝑔 orbital. Through XMCD sum rules and theoretical calculations, we quantified both the spin and orbital magnetic moments. Our study demonstrates that the local electronic structure of the CoO6 octahedra displays an effective trigonal distortion of approximately −0.114 eV. This distortion is larger than the Co 3𝑑 spin-orbit coupling constant, emphasizing the crucial impact of local structural distortions on the electronic and magnetic properties of BaCo2(AsO4)2. | |
Birnkammer, S.; Knap, M.; Knolle, J.; Mook, A.; Bastianello, A. Scattering theory of chiral edge modes in topological magnon insulators Journal Article Phys. Rev. B 112, 094417 (2025). @article{birnkammer_scattering_2025,
title = {Scattering theory of chiral edge modes in topological magnon insulators},
author = {S. Birnkammer and M. Knap and J. Knolle and A. Mook and A. Bastianello},
url = {https://link.aps.org/doi/10.1103/btt2-mp62},
doi = {10.1103/btt2-mp62},
year = {2025},
date = {2025-09-09},
urldate = {2025-09-01},
journal = {Phys. Rev. B},
volume = {112},
number = {9},
pages = {094417},
abstract = {Topological magnon insulators exhibit robust edge modes with chiral properties similar to quantum Hall edge states. However, due to their strong localization at the edges, interactions between these chiral edge magnons can be significant, as we show in a model of coupled magnon-conserving spin chains in an electric field gradient. The chiral edge modes remain edge-localized and do not scatter into the bulk, and we characterize their scattering phase: for strongly localized edge modes, we observe significant deviation from the bare scattering phase. This renormalization of edge scattering can be attributed to bound bulk modes resonating with the chiral edge magnons in the spirit of Feshbach resonances in atomic physics. We argue that the scattering dynamics can be probed experimentally with a real-time measurement protocol using inelastic scanning tunneling spectroscopy. Our results show that interaction among magnons can be encoded in an effective edge model of reduced dimensionality, where the interactions with the bulk renormalize the effective couplings. Our work introduces a systematic way to determine the many-body effective theory for edge states in topological magnon insulators.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
Topological magnon insulators exhibit robust edge modes with chiral properties similar to quantum Hall edge states. However, due to their strong localization at the edges, interactions between these chiral edge magnons can be significant, as we show in a model of coupled magnon-conserving spin chains in an electric field gradient. The chiral edge modes remain edge-localized and do not scatter into the bulk, and we characterize their scattering phase: for strongly localized edge modes, we observe significant deviation from the bare scattering phase. This renormalization of edge scattering can be attributed to bound bulk modes resonating with the chiral edge magnons in the spirit of Feshbach resonances in atomic physics. We argue that the scattering dynamics can be probed experimentally with a real-time measurement protocol using inelastic scanning tunneling spectroscopy. Our results show that interaction among magnons can be encoded in an effective edge model of reduced dimensionality, where the interactions with the bulk renormalize the effective couplings. Our work introduces a systematic way to determine the many-body effective theory for edge states in topological magnon insulators. | |
Huber, N.; Volkau, I.; Engelhardt, A.; Sheikin, I.; Bauer, A.; Pfleiderer, C.; Wilde, M. A. Fermi surface and magnetic breakdown in PdGa Journal Article Phys. Rev. B 112, 085116 (2025). @article{huber_fermi_2025,
title = {Fermi surface and magnetic breakdown in PdGa},
author = {N. Huber and I. Volkau and A. Engelhardt and I. Sheikin and A. Bauer and C. Pfleiderer and M. A. Wilde},
url = {https://link.aps.org/doi/10.1103/kwgt-cryz},
doi = {10.1103/kwgt-cryz},
year = {2025},
date = {2025-08-08},
urldate = {2025-08-01},
journal = {Phys. Rev. B},
volume = {112},
number = {8},
pages = {085116},
abstract = {We study the electronic structure of the chiral semimetal PdGa by means of the de Haas–van Alphen and Shubnikov–de Haas effect. We find that the Fermi surface of PdGa comprises multiple pockets split by spin-orbit coupling. We compare our experimental findings with the band structure calculated ab initio. We demonstrate that the quantum oscillation spectra can be fully understood by considering topological nodal plane degeneracies at the Brillouin zone boundary and magnetic breakdown between individual Fermi-surface pockets. Expanding traditional analysis methods, we explicitly calculate magnetic breakdown frequencies and cyclotron masses while taking into account that extremal breakdown trajectories may reside away from the planes of the single-band orbits. We further analyze high-frequency contributions arising from breakdown trajectories involving multiple revolutions around the Fermi surface which are distinct from conventional harmonic frequencies. Our results highlight the existence of gaps induced by spin-orbit coupling throughout the band structure of PdGa, the relevance of nodal planes on the Brillouin zone boundary, and the necessity for a comprehensive analysis of magnetic breakdown.},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
We study the electronic structure of the chiral semimetal PdGa by means of the de Haas–van Alphen and Shubnikov–de Haas effect. We find that the Fermi surface of PdGa comprises multiple pockets split by spin-orbit coupling. We compare our experimental findings with the band structure calculated ab initio. We demonstrate that the quantum oscillation spectra can be fully understood by considering topological nodal plane degeneracies at the Brillouin zone boundary and magnetic breakdown between individual Fermi-surface pockets. Expanding traditional analysis methods, we explicitly calculate magnetic breakdown frequencies and cyclotron masses while taking into account that extremal breakdown trajectories may reside away from the planes of the single-band orbits. We further analyze high-frequency contributions arising from breakdown trajectories involving multiple revolutions around the Fermi surface which are distinct from conventional harmonic frequencies. Our results highlight the existence of gaps induced by spin-orbit coupling throughout the band structure of PdGa, the relevance of nodal planes on the Brillouin zone boundary, and the necessity for a comprehensive analysis of magnetic breakdown. | |
Rao, P.; Moessner, R.; Knolle, J. Dynamical response theory of interacting Majorana fermions and its application to generic Kitaev quantum spin liquids in a field Journal Article Phys. Rev. B 112, 024440 (2025). @article{rao_dynamical_2025,
title = {Dynamical response theory of interacting Majorana fermions and its application to generic Kitaev quantum spin liquids in a field},
author = {P. Rao and R. Moessner and J. Knolle},
url = {https://link.aps.org/doi/10.1103/f4b4-h1yr},
doi = {10.1103/f4b4-h1yr},
year = {2025},
date = {2025-07-28},
urldate = {2025-07-01},
journal = {Phys. Rev. B},
volume = {112},
number = {2},
pages = {024440},
abstract = {Motivated by the appearance of Majorana fermions in a broad range of correlated and topological electronic systems, we develop a general method to compute the dynamical response of interacting Majorana fermions in the random-phase approximation (RPA). This can be applied self-consistently on top of Majorana mean-field theory backgrounds, thereby in particular providing a powerful tool to analyze generic behavior in the vicinity of (various heavily studied) exactly soluble models. Prime examples are quantum spin liquids (QSL) with emergent Majorana excitations, with the celebrated exact solution of Kitaev. We employ the RPA to study in considerable detail phase structure and dynamics of the extended Kitaev honeycomb 𝐾𝐽Γ model, with and without an applied field. First, we benchmark our method with Kitaev's exactly soluble model, finding a remarkable agreement. The interactions between Majorana fermions even turn out to mimic the effect of local ℤ2 flux excitations, which we explain analytically. Second, we show how small non-Kitaev couplings 𝐽 and Γ induce Majorana bound states, resulting in sharp features in the dynamical structure factor in the presence of fractionalization: such “spinon excitons” naturally appear, and can coexist and interact with the broad Majorana continuum. Third, for increasing couplings or field, our theory predicts instabilities of the Kitaev QSL (KQSL) triggered by the condensation of the sharp modes. From the high-symmetry momenta of the condensation we can deduce which magnetically ordered phases surround the KQSL, in good agreement with previous finite-size numerics. We discuss implications for experiments and the broad range of applicability of our method to other QSL and Majorana systems.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
Motivated by the appearance of Majorana fermions in a broad range of correlated and topological electronic systems, we develop a general method to compute the dynamical response of interacting Majorana fermions in the random-phase approximation (RPA). This can be applied self-consistently on top of Majorana mean-field theory backgrounds, thereby in particular providing a powerful tool to analyze generic behavior in the vicinity of (various heavily studied) exactly soluble models. Prime examples are quantum spin liquids (QSL) with emergent Majorana excitations, with the celebrated exact solution of Kitaev. We employ the RPA to study in considerable detail phase structure and dynamics of the extended Kitaev honeycomb 𝐾𝐽Γ model, with and without an applied field. First, we benchmark our method with Kitaev's exactly soluble model, finding a remarkable agreement. The interactions between Majorana fermions even turn out to mimic the effect of local ℤ2 flux excitations, which we explain analytically. Second, we show how small non-Kitaev couplings 𝐽 and Γ induce Majorana bound states, resulting in sharp features in the dynamical structure factor in the presence of fractionalization: such “spinon excitons” naturally appear, and can coexist and interact with the broad Majorana continuum. Third, for increasing couplings or field, our theory predicts instabilities of the Kitaev QSL (KQSL) triggered by the condensation of the sharp modes. From the high-symmetry momenta of the condensation we can deduce which magnetically ordered phases surround the KQSL, in good agreement with previous finite-size numerics. We discuss implications for experiments and the broad range of applicability of our method to other QSL and Majorana systems. | |
Papaefstathiou, I.; Malz, D.; Cirac, J. I.; Bañuls, M. C. Efficient tensor network simulation of multiemitter non-Markovian systems Journal Article Phys. Rev. A 112, 013721 (2025). @article{papaefstathiou_efficient_2025,
title = {Efficient tensor network simulation of multiemitter non-Markovian systems},
author = {I. Papaefstathiou and D. Malz and J. I. Cirac and M. C. Bañuls},
url = {https://link.aps.org/doi/10.1103/hmbj-lg7p},
doi = {10.1103/hmbj-lg7p},
year = {2025},
date = {2025-07-24},
urldate = {2025-07-24},
journal = {Phys. Rev. A},
volume = {112},
number = {1},
pages = {013721},
keywords = {C5},
pubstate = {published},
tppubtype = {article}
}
| |
Schilberth, F.; Jiang, M. -C.; Mardelé, F. Le; Papp, L. B.; Mohelsky, I.; Kassem, M. A.; Tabata, Y.; Waki, T.; Nakamura, H.; Guo, G. -Y.; Orlita, M.; Arita, R.; Kézsmárki, I.; Bordács, S. Generation of a nodal line and Weyl points by magnetization reorientation in Co3Sn2S2 Journal Article npj Quantum Mater. 10, 67 (2025). @article{schilberth_generation_2025,
title = {Generation of a nodal line and Weyl points by magnetization reorientation in Co_{3}Sn_{2}S_{2}},
author = {F. Schilberth and M. -C. Jiang and F. Le Mardelé and L. B. Papp and I. Mohelsky and M. A. Kassem and Y. Tabata and T. Waki and H. Nakamura and G. -Y. Guo and M. Orlita and R. Arita and I. Kézsmárki and S. Bordács},
url = {https://doi.org/10.1038/s41535-025-00785-0},
doi = {10.1038/s41535-025-00785-0},
year = {2025},
date = {2025-07-01},
urldate = {2025-07-01},
journal = {npj Quantum Mater.},
volume = {10},
number = {1},
pages = {67},
abstract = {Topological magnets exhibit fascinating physics like topologically protected surface states and anomalous transport. Although these states and phenomena are expected to strongly depend on the magnetic order, their experimental manipulation has been scarcely studied. Here, we demonstrate the magnetic field control of the topological band structure in Co3Sn2S2 by magneto-optical spectroscopy. We resolve a magnetic field-induced redshift of the nodal loop resonance as the magnetization is rotated into the kagome plane. Our material-specific theory, capturing the observed field-induced spectral reconstruction, reveals the emergence of a gapless nodal loop for one of the in-plane magnetization directions. The calculations show that the additionally created Weyl points for in-plane fields marginally contribute to the optical response. These findings demonstrate that breaking underlying crystal symmetries with external fields provides an efficient way to manipulate topological band features. Moreover, our results highlight the potential of low-energy magneto-optical spectroscopy in probing variations of quantum geometry.},
keywords = {A1},
pubstate = {published},
tppubtype = {article}
}
Topological magnets exhibit fascinating physics like topologically protected surface states and anomalous transport. Although these states and phenomena are expected to strongly depend on the magnetic order, their experimental manipulation has been scarcely studied. Here, we demonstrate the magnetic field control of the topological band structure in Co3Sn2S2 by magneto-optical spectroscopy. We resolve a magnetic field-induced redshift of the nodal loop resonance as the magnetization is rotated into the kagome plane. Our material-specific theory, capturing the observed field-induced spectral reconstruction, reveals the emergence of a gapless nodal loop for one of the in-plane magnetization directions. The calculations show that the additionally created Weyl points for in-plane fields marginally contribute to the optical response. These findings demonstrate that breaking underlying crystal symmetries with external fields provides an efficient way to manipulate topological band features. Moreover, our results highlight the potential of low-energy magneto-optical spectroscopy in probing variations of quantum geometry. | |
Sharma, S.; Chioncel, L.; Marco, I. Di Exploring strong electronic correlations in the breathing kagome metal Fe3Sn Journal Article Phys. Rev. B 111, 235127 (2025). @article{sharma_exploring_2025,
title = {Exploring strong electronic correlations in the breathing kagome metal Fe_{3}Sn},
author = {S. Sharma and L. Chioncel and I. Di Marco},
url = {https://link.aps.org/doi/10.1103/xmmr-mfv4},
doi = {10.1103/xmmr-mfv4},
year = {2025},
date = {2025-06-16},
urldate = {2025-06-16},
journal = {Phys. Rev. B},
volume = {111},
number = {23},
pages = {235127},
abstract = {Kagome metals have emerged as pivotal materials in condensed matter physics due to their unique geometric arrangement and intriguing electronic properties. Understanding the origin of magnetism in these materials, particularly in iron-rich Fe-Sn binary compounds such as Fe3Sn, holds a significant importance, as they represent potential candidates for permanent magnets with a high Curie temperature and a strong magnetic anisotropy. In the present study, we employ density functional theory and dynamical mean-field theory to analyze the electronic structure and magnetic properties of Fe3Sn. Our investigation reveals the presence of several nearly flat bands and Weyl nodes at low excitation energies. The inclusion of local correlation effects is shown to push these features even closer to the Fermi energy, which may be important for their manipulation via external stimuli. Regarding magnetism, the Hubbard-like interaction leads to an increase of orbital polarization at the expenses of a minor reduction of the spin moment. The magnetic anisotropy energy exhibits a strong dependence on the particular choice of the Coulomb interaction parameters. Additionally, our detailed analysis of the interatomic exchange interactions indicates a significant contribution from the antisymmetric exchange, i.e., the Dzyaloshinskii-Moriya interaction, which showcases the existence of magnetic chirality in the system. Overall, our investigation highlights a strong interplay between the flat bands near the Fermi level, the local Coulomb interaction, and the triangular geometry of the lattice, which plays a crucial role in driving the magnetic properties of this material.},
keywords = {A5},
pubstate = {published},
tppubtype = {article}
}
Kagome metals have emerged as pivotal materials in condensed matter physics due to their unique geometric arrangement and intriguing electronic properties. Understanding the origin of magnetism in these materials, particularly in iron-rich Fe-Sn binary compounds such as Fe3Sn, holds a significant importance, as they represent potential candidates for permanent magnets with a high Curie temperature and a strong magnetic anisotropy. In the present study, we employ density functional theory and dynamical mean-field theory to analyze the electronic structure and magnetic properties of Fe3Sn. Our investigation reveals the presence of several nearly flat bands and Weyl nodes at low excitation energies. The inclusion of local correlation effects is shown to push these features even closer to the Fermi energy, which may be important for their manipulation via external stimuli. Regarding magnetism, the Hubbard-like interaction leads to an increase of orbital polarization at the expenses of a minor reduction of the spin moment. The magnetic anisotropy energy exhibits a strong dependence on the particular choice of the Coulomb interaction parameters. Additionally, our detailed analysis of the interatomic exchange interactions indicates a significant contribution from the antisymmetric exchange, i.e., the Dzyaloshinskii-Moriya interaction, which showcases the existence of magnetic chirality in the system. Overall, our investigation highlights a strong interplay between the flat bands near the Fermi level, the local Coulomb interaction, and the triangular geometry of the lattice, which plays a crucial role in driving the magnetic properties of this material. | |
Natori, W.; Yang, Y.; Jin, H. -K.; Knolle, J.; Perkins, N. B. Ferrimagnetic Kitaev spin liquids in mixed spin-1/2 and spin-3/2 honeycomb magnets Journal Article Phys. Rev. B 111, 214411 (2025). @article{natori_ferrimagnetic_2025,
title = {Ferrimagnetic Kitaev spin liquids in mixed spin-1/2 and spin-3/2 honeycomb magnets},
author = {W. Natori and Y. Yang and H. -K. Jin and J. Knolle and N. B. Perkins},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.214411},
doi = {10.1103/PhysRevB.111.214411},
year = {2025},
date = {2025-06-04},
urldate = {2025-06-01},
journal = {Phys. Rev. B},
volume = {111},
number = {21},
pages = {214411},
abstract = {We explore the phase diagram of a mixed-spin Kitaev model, where spin-1/2 and spin-3/2 ions form a staggered pattern on a honeycomb lattice. Enabled by an exact mapping of local conserved flux operators onto 𝑍2 gauge fields, we perform a parton mean-field theory for the model with a single-ion anisotropy. The phase diagram contains four types of quantum spin liquids distinguished by quadrupolar parameters. These analytical results are quantitatively confirmed by state-of-the-art DMRG simulations. We also explore the potential experimental realization of the mixed-spin Kitaev model in materials such as Zr0.5Ru0.5Cl3. By developing a superexchange theory specifically for this mixed-spin system, we identify the conditions under which dominant Kitaev-like interactions emerge. Our findings highlight the importance of spin-orbital couplings and quadrupolar order parameters in stabilizing exotic phases, providing a foundation for exploring mixed-spin Kitaev magnets.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
We explore the phase diagram of a mixed-spin Kitaev model, where spin-1/2 and spin-3/2 ions form a staggered pattern on a honeycomb lattice. Enabled by an exact mapping of local conserved flux operators onto 𝑍2 gauge fields, we perform a parton mean-field theory for the model with a single-ion anisotropy. The phase diagram contains four types of quantum spin liquids distinguished by quadrupolar parameters. These analytical results are quantitatively confirmed by state-of-the-art DMRG simulations. We also explore the potential experimental realization of the mixed-spin Kitaev model in materials such as Zr0.5Ru0.5Cl3. By developing a superexchange theory specifically for this mixed-spin system, we identify the conditions under which dominant Kitaev-like interactions emerge. Our findings highlight the importance of spin-orbital couplings and quadrupolar order parameters in stabilizing exotic phases, providing a foundation for exploring mixed-spin Kitaev magnets. | |
Parshukov, K.; Wiedmann, R.; Schnyder, A. P. Topological crossings in two-dimensional altermagnets: Symmetry classification and topological responses Journal Article Phys. Rev. B 111, 224406 (2025). @article{parshukov_topological_2025,
title = {Topological crossings in two-dimensional altermagnets: Symmetry classification and topological responses},
author = {K. Parshukov and R. Wiedmann and A. P. Schnyder},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.224406},
doi = {10.1103/PhysRevB.111.224406},
year = {2025},
date = {2025-06-04},
urldate = {2025-06-01},
journal = {Phys. Rev. B},
volume = {111},
number = {22},
pages = {224406},
abstract = {We study the symmetry requirements for topologically protected spin-polarized Dirac points in 2D altermagnets. The topology is characterized by a quantized 𝜋-Berry phase and the degeneracy is protected by spin-space group symmetries. Gapped phases with finite Chern and/or spin/chirality Chern numbers emerge under different symmetry-breaking mass terms. We investigate the surface and transport properties of these gapped phases using representative electronic tight-binding and magnonic linear spin-wave models. In particular, we calculate the electronic and magnonic Hall currents and discuss implications for experiments.},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
We study the symmetry requirements for topologically protected spin-polarized Dirac points in 2D altermagnets. The topology is characterized by a quantized 𝜋-Berry phase and the degeneracy is protected by spin-space group symmetries. Gapped phases with finite Chern and/or spin/chirality Chern numbers emerge under different symmetry-breaking mass terms. We investigate the surface and transport properties of these gapped phases using representative electronic tight-binding and magnonic linear spin-wave models. In particular, we calculate the electronic and magnonic Hall currents and discuss implications for experiments. | |
Prodan, L.; Evans, D. M.; Sukhanov, A. S.; Nikitin, S. E.; Tsirlin, A. A.; Puntigam, L.; Rahn, M. C.; Chioncel, L.; Tsurkan, V.; Kézsmárki, I. Easy-cone state mediating the spin reorientation in the topological kagome magnet Fe3Sn2 Journal Article Phys. Rev. B 111, 184442 (2025). @article{prodan_easy-cone_2025,
title = {Easy-cone state mediating the spin reorientation in the topological kagome magnet Fe_{3}Sn_{2}},
author = {L. Prodan and D. M. Evans and A. S. Sukhanov and S. E. Nikitin and A. A. Tsirlin and L. Puntigam and M. C. Rahn and L. Chioncel and V. Tsurkan and I. Kézsmárki},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.184442},
doi = {10.1103/PhysRevB.111.184442},
year = {2025},
date = {2025-05-30},
urldate = {2025-05-01},
journal = {Phys. Rev. B},
volume = {111},
number = {18},
pages = {184442},
abstract = {We investigated temperature-driven spin reorientation (SR) in the itinerant kagome magnet Fe3Sn2 using high-resolution synchrotron x-ray diffraction, neutron diffraction, magnetometry, and magnetic force microscopy (MFM), further supported by phenomenological analysis. Our study reveals a crossover from the state with easy-plane anisotropy to the high-temperature state with uniaxial easy-axis anisotropy taking place between ∼40 and 130 K through an intermediate easy-cone (or tilted spin) state. This state, induced by the interplay between the anisotropy constants 𝐾1 and 𝐾2, is clearly manifested in the thermal evolution of the magnetic structure factor, which reveals a gradual change of the SR angle 𝜃 between 40 and 130 K. We also found that the SR is accompanied by a magnetoelastic effect. Zero-field MFM images across the SR range show a transformation in surface magnetic patterns from a dendritic structure at 120 K to domain-wall-dominated MFM contrast at 40 K. Our analysis suggests that the SR and associated microstructural transformations are the results of competing first- and second-order anisotropy constants.},
keywords = {A4, B1},
pubstate = {published},
tppubtype = {article}
}
We investigated temperature-driven spin reorientation (SR) in the itinerant kagome magnet Fe3Sn2 using high-resolution synchrotron x-ray diffraction, neutron diffraction, magnetometry, and magnetic force microscopy (MFM), further supported by phenomenological analysis. Our study reveals a crossover from the state with easy-plane anisotropy to the high-temperature state with uniaxial easy-axis anisotropy taking place between ∼40 and 130 K through an intermediate easy-cone (or tilted spin) state. This state, induced by the interplay between the anisotropy constants 𝐾1 and 𝐾2, is clearly manifested in the thermal evolution of the magnetic structure factor, which reveals a gradual change of the SR angle 𝜃 between 40 and 130 K. We also found that the SR is accompanied by a magnetoelastic effect. Zero-field MFM images across the SR range show a transformation in surface magnetic patterns from a dendritic structure at 120 K to domain-wall-dominated MFM contrast at 40 K. Our analysis suggests that the SR and associated microstructural transformations are the results of competing first- and second-order anisotropy constants. |  |
Sakrikar, P.; Shen, B.; Poldi, Eduardo H. T.; Bahrami, F.; Hu, X.; Kenney, E. M.; Wang, Q.; Fruhling, K. W.; Wang, C.; Gupta, R.; Khasanov, R.; Luetkens, H.; Calder, S. A.; Aczel, A. A.; Fabbris, G.; Hemley, R. J.; Plumb, K. W.; Ran, Y.; Gegenwart, P.; Tsirlin, A. A.; Haskel, D.; Graf, M. J.; Tafti, F. Pressure tuning of competing interactions on a honeycomb lattice Journal Article Nat. Commun. 16, 4712 (2025). @article{sakrikar_pressure_2025,
title = {Pressure tuning of competing interactions on a honeycomb lattice},
author = {P. Sakrikar and B. Shen and Eduardo H. T. Poldi and F. Bahrami and X. Hu and E. M. Kenney and Q. Wang and K. W. Fruhling and C. Wang and R. Gupta and R. Khasanov and H. Luetkens and S. A. Calder and A. A. Aczel and G. Fabbris and R. J. Hemley and K. W. Plumb and Y. Ran and P. Gegenwart and A. A. Tsirlin and D. Haskel and M. J. Graf and F. Tafti},
url = {https://doi.org/10.1038/s41467-025-59897-7},
doi = {10.1038/s41467-025-59897-7},
year = {2025},
date = {2025-05-21},
urldate = {2025-05-21},
journal = {Nat. Commun.},
volume = {16},
number = {1},
pages = {4712},
abstract = {Exchange interactions are mediated via orbital overlaps across chemical bonds. Thus, modifying the bond angles by physical pressure or strain can tune the relative strength of competing interactions. Here we present a remarkable case of such tuning between the Heisenberg (J) and Kitaev (K) exchange, which respectively establish magnetically ordered and spin liquid phases on a honeycomb lattice. We observe a rapid suppression of the Néel temperature (TN) with pressure in Ag3LiRh2O6, a spin-1/2 honeycomb lattice with both J and K couplings. Using a combined analysis of x-ray data and first-principles calculations, we find that pressure modifies the bond angles in a way that increases the ∣K/J∣ ratio and thereby suppresses TN. Consistent with this picture, we observe a spontaneous onset of muon spin relaxation (μSR) oscillations below TN at low pressure, whereas in the high pressure phase, oscillations appear only when T < TN/2. Unlike other candidate Kitaev materials, Ag3LiRh2O6is tuned toward a quantum critical point by pressure while avoiding a structural dimerization in the relevant pressure range.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
Exchange interactions are mediated via orbital overlaps across chemical bonds. Thus, modifying the bond angles by physical pressure or strain can tune the relative strength of competing interactions. Here we present a remarkable case of such tuning between the Heisenberg (J) and Kitaev (K) exchange, which respectively establish magnetically ordered and spin liquid phases on a honeycomb lattice. We observe a rapid suppression of the Néel temperature (TN) with pressure in Ag3LiRh2O6, a spin-1/2 honeycomb lattice with both J and K couplings. Using a combined analysis of x-ray data and first-principles calculations, we find that pressure modifies the bond angles in a way that increases the ∣K/J∣ ratio and thereby suppresses TN. Consistent with this picture, we observe a spontaneous onset of muon spin relaxation (μSR) oscillations below TN at low pressure, whereas in the high pressure phase, oscillations appear only when T < TN/2. Unlike other candidate Kitaev materials, Ag3LiRh2O6is tuned toward a quantum critical point by pressure while avoiding a structural dimerization in the relevant pressure range. | |
Xu, W. -T.; Pollmann, F.; Knap, M. Critical behavior of Fredenhagen-Marcu string order parameters at topological phase transitions with emergent higher-form symmetries Journal Article npj Quantum Inf. 11, 74 (2025). @article{xu_critical_2025,
title = {Critical behavior of Fredenhagen-Marcu string order parameters at topological phase transitions with emergent higher-form symmetries},
author = {W. -T. Xu and F. Pollmann and M. Knap},
url = {https://doi.org/10.1038/s41534-025-01030-z},
doi = {10.1038/s41534-025-01030-z},
year = {2025},
date = {2025-05-09},
urldate = {2025-05-01},
journal = {npj Quantum Inf.},
volume = {11},
number = {1},
pages = {74},
abstract = {A nonlocal string order parameter detecting topological order and deconfinement has been proposed by Fredenhagen and Marcu (FM). However, due to the lack of exact internal symmetries for lattice models and the nonlinear dependence of the FM string order parameter on ground states, it is a priori not guaranteed that it is a genuine order parameter for topological phase transitions. In this work, we find that the FM string order parameter exhibits universal scaling behavior near critical points of charge condensation transitions, by directly evaluating the FM string order parameter in the infinite string-length limit using infinite Projected Entangled Pair States (iPEPS) for the toric code in a magnetic field. Our results thus demonstrate that the FM string order parameter represents a quantitatively well-behaved order parameter. We find that only in the presence of an emergent 1-form symmetry the corresponding FM string order parameter can faithfully detect topological transitions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A nonlocal string order parameter detecting topological order and deconfinement has been proposed by Fredenhagen and Marcu (FM). However, due to the lack of exact internal symmetries for lattice models and the nonlinear dependence of the FM string order parameter on ground states, it is a priori not guaranteed that it is a genuine order parameter for topological phase transitions. In this work, we find that the FM string order parameter exhibits universal scaling behavior near critical points of charge condensation transitions, by directly evaluating the FM string order parameter in the infinite string-length limit using infinite Projected Entangled Pair States (iPEPS) for the toric code in a magnetic field. Our results thus demonstrate that the FM string order parameter represents a quantitatively well-behaved order parameter. We find that only in the presence of an emergent 1-form symmetry the corresponding FM string order parameter can faithfully detect topological transitions. | |
Szaller, D.; Prodan, L.; Geirhos, K.; Felea, V.; Skourski, Y.; Gorbunov, D.; Förster, T.; Helm, T.; Nomura, T.; Miyata, A.; Zherlitsyn, S.; Wosnitza, J.; Tsirlin, A. A.; Tsurkan, V.; Kézsmárki, I. Coexistence of antiferromagnetism and ferrimagnetism in adjacent honeycomb layers Journal Article Phys. Rev. B 111, 184404 (2025). @article{szaller_coexistence_2025,
title = {Coexistence of antiferromagnetism and ferrimagnetism in adjacent honeycomb layers},
author = {D. Szaller and L. Prodan and K. Geirhos and V. Felea and Y. Skourski and D. Gorbunov and T. Förster and T. Helm and T. Nomura and A. Miyata and S. Zherlitsyn and J. Wosnitza and A. A. Tsirlin and V. Tsurkan and I. Kézsmárki},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.184404},
doi = {10.1103/PhysRevB.111.184404},
year = {2025},
date = {2025-05-02},
urldate = {2025-05-02},
journal = {Phys. Rev. B},
volume = {111},
number = {18},
pages = {184404},
abstract = {Ferro-/ferri- and antiferromagnetically ordered phases are typically exclusive in nature, thus, their coexistence in atomic-scale proximity is expected only in heterostructures. Breaking this paradigm and broadening the range of unconventional magnetic states, we report here on the observation of a new, atomic-scale hybrid spin state. This ordering is stabilized in three-dimensional crystals of the polar antiferromagnet Co2Mo3O8 by magnetic fields applied perpendicular to the Co honeycomb layers and possesses a spontaneous in-plane ferromagnetic moment. Our microscopic spin model, capturing the observed field dependence of the longitudinal and transverse magnetization as well as the magnetoelectric/elastic properties, reveals that this novel spin state is composed of an alternating stacking of antiferromagnetic and ferrimagnetic honeycomb layers. The strong intralayer and the weak interlayer exchange couplings together with competing anisotropies at octahedral and tetrahedral Co sites are identified as the key ingredients to stabilize antiferromagnetic and ferrimagnetic layers in such close proximity. We show that the proper balance of magnetic interactions can extend the stability range of this hybrid phase down to zero magnetic field. The possibility to realize a layer-by-layer stacking of such distinct spin orders via suitable combinations of microscopic interactions opens a new dimension toward the nanoscale engineering of magnetic states.},
keywords = {B1, C2},
pubstate = {published},
tppubtype = {article}
}
Ferro-/ferri- and antiferromagnetically ordered phases are typically exclusive in nature, thus, their coexistence in atomic-scale proximity is expected only in heterostructures. Breaking this paradigm and broadening the range of unconventional magnetic states, we report here on the observation of a new, atomic-scale hybrid spin state. This ordering is stabilized in three-dimensional crystals of the polar antiferromagnet Co2Mo3O8 by magnetic fields applied perpendicular to the Co honeycomb layers and possesses a spontaneous in-plane ferromagnetic moment. Our microscopic spin model, capturing the observed field dependence of the longitudinal and transverse magnetization as well as the magnetoelectric/elastic properties, reveals that this novel spin state is composed of an alternating stacking of antiferromagnetic and ferrimagnetic honeycomb layers. The strong intralayer and the weak interlayer exchange couplings together with competing anisotropies at octahedral and tetrahedral Co sites are identified as the key ingredients to stabilize antiferromagnetic and ferrimagnetic layers in such close proximity. We show that the proper balance of magnetic interactions can extend the stability range of this hybrid phase down to zero magnetic field. The possibility to realize a layer-by-layer stacking of such distinct spin orders via suitable combinations of microscopic interactions opens a new dimension toward the nanoscale engineering of magnetic states. |  |
Kern, L. -M.; Kuchkin, V. M.; Deinhart, V.; Klose, C.; Sidiropoulos, T.; Auer, M.; Gaebel, S.; Gerlinger, K.; Battistelli, R.; Wittrock, S.; Karaman, T.; Schneider, M.; Günther, C. M.; Engel, D.; Will, I.; Wintz, S.; Weigand, M.; Büttner, F.; Höflich, K.; Eisebitt, S.; Pfau, B. Controlled Formation of Skyrmion Bags Journal Article Adv. Mater. 2501250 (2025), (contributed). @article{kern_controlled_2025,
title = {Controlled Formation of Skyrmion Bags},
author = {L. -M. Kern and V. M. Kuchkin and V. Deinhart and C. Klose and T. Sidiropoulos and M. Auer and S. Gaebel and K. Gerlinger and R. Battistelli and S. Wittrock and T. Karaman and M. Schneider and C. M. Günther and D. Engel and I. Will and S. Wintz and M. Weigand and F. Büttner and K. Höflich and S. Eisebitt and B. Pfau},
url = {https://advanced.onlinelibrary.wiley.com/doi/abs/10.1002/adma.202501250},
doi = {10.1002/adma.202501250},
year = {2025},
date = {2025-04-28},
urldate = {2025-04-01},
journal = {Adv. Mater.},
pages = {2501250},
abstract = {Abstract Topologically non-trivial magnetic solitons are complex spin textures with a distinct single-particle nature. Although magnetic skyrmions, especially those with unity topological charge, have attracted substantial interest due to their potential applications, more complex topological textures remain largely theoretical. In this work, the stabilization of isolated higher-order skyrmion bags beyond the prototypical π-skyrmion in ferromagnetic thin films is experimentally demonstrate, which has posed considerable challenges to date. Specifically, controlled generation of skyrmionium (2π-skyrmion), target skyrmion (3π-skyrmion), and skyrmion bags (with variable topological charge) are achieved through the introduction of artificially engineered anisotropy defects via local ion irradiation. They act as preferential sites for the field- or laser-induced nucleation of skyrmion bags. Remarkably, ultrafast laser pulses achieve a substantially higher conversion rate transforming skyrmions into higher-order skyrmion bags compared to their formation driven by magnetic fields. High-resolution x-ray imaging enables direct observation of the resulting skyrmion bags. Complementary micromagnetic simulations reveal the pivotal role of defect geometry–particularly diameter–in stabilizing closed-loop domain textures. The findings not only broaden the experimental horizon for skyrmion research, but also suggest strategies for exploiting complex topological spin textures within a unified material platform for practical applications.},
note = {(contributed)},
keywords = {C2},
pubstate = {published},
tppubtype = {article}
}
Abstract Topologically non-trivial magnetic solitons are complex spin textures with a distinct single-particle nature. Although magnetic skyrmions, especially those with unity topological charge, have attracted substantial interest due to their potential applications, more complex topological textures remain largely theoretical. In this work, the stabilization of isolated higher-order skyrmion bags beyond the prototypical π-skyrmion in ferromagnetic thin films is experimentally demonstrate, which has posed considerable challenges to date. Specifically, controlled generation of skyrmionium (2π-skyrmion), target skyrmion (3π-skyrmion), and skyrmion bags (with variable topological charge) are achieved through the introduction of artificially engineered anisotropy defects via local ion irradiation. They act as preferential sites for the field- or laser-induced nucleation of skyrmion bags. Remarkably, ultrafast laser pulses achieve a substantially higher conversion rate transforming skyrmions into higher-order skyrmion bags compared to their formation driven by magnetic fields. High-resolution x-ray imaging enables direct observation of the resulting skyrmion bags. Complementary micromagnetic simulations reveal the pivotal role of defect geometry–particularly diameter–in stabilizing closed-loop domain textures. The findings not only broaden the experimental horizon for skyrmion research, but also suggest strategies for exploiting complex topological spin textures within a unified material platform for practical applications. | |
Metternich, D.; Litzius, K.; Wintz, S.; Gerlinger, K.; Petz, S.; Engel, D.; Sidiropoulos, T.; Battistelli, R.; Steinbach, F.; Weigand, M.; Wittrock, S.; Schmising, C. Korff; Büttner, F. Defects in magnetic domain walls after single-shot all-optical switching Journal Article Struct. Dyn. 12, 024504 (2025). @article{metternich_defects_2025,
title = {Defects in magnetic domain walls after single-shot all-optical switching},
author = {D. Metternich and K. Litzius and S. Wintz and K. Gerlinger and S. Petz and D. Engel and T. Sidiropoulos and R. Battistelli and F. Steinbach and M. Weigand and S. Wittrock and C. Korff Schmising and F. Büttner},
url = {https://doi.org/10.1063/4.0000287},
doi = {10.1063/4.0000287},
year = {2025},
date = {2025-04-18},
urldate = {2025-04-01},
journal = {Struct. Dyn.},
volume = {12},
number = {2},
pages = {024504},
abstract = {Helicity-independent all-optical switching (HI-AOS) is the fastest known way to switch the magnetic order parameter. While the switching process of extended areas is well understood, the formation of domain walls enclosing switched areas remains less explored. Here, we study domain walls around all-optically nucleated magnetic domains using x-ray vector spin imaging and observe a high density of vertical Bloch line defects. Surprisingly, the defect density appears to be independent of optical pulse parameters, significantly varies between materials, and is only slightly higher than in domain walls generated by field cycling. A possible explanation is given by time-resolved Kerr microscopy, which reveals that magnetic domains considerably expand after the initial AOS process. During this expansion, and likewise during field cycling, domain walls propagate at speeds above the Walker breakdown. Micromagnetic simulations suggest that at such speeds, domain walls accumulate defects when moving over magnetic pinning sites, explaining similar defect densities after two very different switching processes. The slightly larger defect density after AOS compared to field-induced switching indicates that some defects are created already when the domain wall comes into existence. Our work shows that engineered low-pinning materials are a key ingredient to uncover the intrinsic dynamics of domain wall formation during ultrafast all-optical switching.},
keywords = {C2},
pubstate = {published},
tppubtype = {article}
}
Helicity-independent all-optical switching (HI-AOS) is the fastest known way to switch the magnetic order parameter. While the switching process of extended areas is well understood, the formation of domain walls enclosing switched areas remains less explored. Here, we study domain walls around all-optically nucleated magnetic domains using x-ray vector spin imaging and observe a high density of vertical Bloch line defects. Surprisingly, the defect density appears to be independent of optical pulse parameters, significantly varies between materials, and is only slightly higher than in domain walls generated by field cycling. A possible explanation is given by time-resolved Kerr microscopy, which reveals that magnetic domains considerably expand after the initial AOS process. During this expansion, and likewise during field cycling, domain walls propagate at speeds above the Walker breakdown. Micromagnetic simulations suggest that at such speeds, domain walls accumulate defects when moving over magnetic pinning sites, explaining similar defect densities after two very different switching processes. The slightly larger defect density after AOS compared to field-induced switching indicates that some defects are created already when the domain wall comes into existence. Our work shows that engineered low-pinning materials are a key ingredient to uncover the intrinsic dynamics of domain wall formation during ultrafast all-optical switching. | |
Mangeolle, L.; Knolle, J. Anomalous Quantum Oscillations from Boson-Mediated Interband Scattering Journal Article Phys. Rev. Lett. 134, 146502 (2025). @article{mangeolle_anomalous_2025-1,
title = {Anomalous Quantum Oscillations from Boson-Mediated Interband Scattering},
author = {L. Mangeolle and J. Knolle},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.134.146502},
doi = {10.1103/PhysRevLett.134.146502},
year = {2025},
date = {2025-04-09},
urldate = {2025-04-01},
journal = {Phys. Rev. Lett.},
volume = {134},
number = {14},
pages = {146502},
abstract = {Quantum oscillations (QOs) in metals refer to the periodic variation of thermodynamic and transport properties as a function of inverse applied magnetic field. QO frequencies are normally associated with semiclassical trajectories of Fermi surface orbits, but recent experiments challenge the canonical description. We develop a theory of composite frequency quantum oscillations (CFQOs) in two-dimensional Fermi liquids with several Fermi surfaces and interband scattering mediated by a dynamical boson, e.g., phonons or spin fluctuations. Specifically, we show that CFQOs arise from oscillations in the fermionic self-energy with anomalous frequency splitting and distinct strongly non-Lifshitz–Kosevich temperature dependences. Our theory goes beyond the framework of semiclassical Fermi surface trajectories highlighting the role of interaction effects. We provide experimental predictions and discuss the effect of nonequilibrium boson occupation in driven systems.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
Quantum oscillations (QOs) in metals refer to the periodic variation of thermodynamic and transport properties as a function of inverse applied magnetic field. QO frequencies are normally associated with semiclassical trajectories of Fermi surface orbits, but recent experiments challenge the canonical description. We develop a theory of composite frequency quantum oscillations (CFQOs) in two-dimensional Fermi liquids with several Fermi surfaces and interband scattering mediated by a dynamical boson, e.g., phonons or spin fluctuations. Specifically, we show that CFQOs arise from oscillations in the fermionic self-energy with anomalous frequency splitting and distinct strongly non-Lifshitz–Kosevich temperature dependences. Our theory goes beyond the framework of semiclassical Fermi surface trajectories highlighting the role of interaction effects. We provide experimental predictions and discuss the effect of nonequilibrium boson occupation in driven systems. | |
Hua, N.; Breitner, F.; Jesche, A.; Huang, S. -W.; Rüegg, C.; Gegenwart, P. Structural and magnetic properties of β-Li2IrO3 after grazing-angle focused ion beam thinning Journal Article Acta Crystallogr. B 81, 202 (2025). @article{hua_structural_2025,
title = {Structural and magnetic properties of β-Li_{2}IrO_{3} after grazing-angle focused ion beam thinning},
author = {N. Hua and F. Breitner and A. Jesche and S. -W. Huang and C. Rüegg and P. Gegenwart},
url = {https://doi.org/10.1107/S2052520625000587},
doi = {10.1107/S2052520625000587},
year = {2025},
date = {2025-04-01},
urldate = {2025-04-01},
journal = {Acta Crystallogr. B},
volume = {81},
number = {2},
pages = {202},
abstract = {Manipulating the size and orientation of quantum materials is often used to tune emergent phenomena, but precise control of these parameters is also necessary from an experimental point of view. Various synthesis techniques already exist, such as epitaxial thin film growth and chemical etching, that are capable of producing specific sample dimensions with high precision. However, certain materials exist as single crystals that are often difficult to manipulate, thereby limiting their studies to a certain subset of experimental techniques. One particular class of these materials includes lithium and sodium iridates, which are promising candidates for hosting a Kitaev quantum spin liquid state. Here a controlled method of using a focused ion beam at grazing incidence to reduce the size of a β-Li_2IrO_3 single crystal to a thickness of 1–2𝜇m is presented. Subsequent X-ray diffraction measurements show the lattice remains intact, albeit with a larger mosaic spread. The integrity of the magnetic order is also preserved as the temperature dependent magnetic diffraction peak follows the same trend as its bulk counterpart with a transition temperature at textitT = 37.5K. Our study demonstrates a technique that opens up the possibility of nonequilibrium experiments where submicron thin samples are often essential.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
Manipulating the size and orientation of quantum materials is often used to tune emergent phenomena, but precise control of these parameters is also necessary from an experimental point of view. Various synthesis techniques already exist, such as epitaxial thin film growth and chemical etching, that are capable of producing specific sample dimensions with high precision. However, certain materials exist as single crystals that are often difficult to manipulate, thereby limiting their studies to a certain subset of experimental techniques. One particular class of these materials includes lithium and sodium iridates, which are promising candidates for hosting a Kitaev quantum spin liquid state. Here a controlled method of using a focused ion beam at grazing incidence to reduce the size of a β-Li_2IrO_3 single crystal to a thickness of 1–2𝜇m is presented. Subsequent X-ray diffraction measurements show the lattice remains intact, albeit with a larger mosaic spread. The integrity of the magnetic order is also preserved as the temperature dependent magnetic diffraction peak follows the same trend as its bulk counterpart with a transition temperature at textitT = 37.5K. Our study demonstrates a technique that opens up the possibility of nonequilibrium experiments where submicron thin samples are often essential. | |
Vivanco, F. J.; Schuckert, A.; Huang, S.; Schumacher, G. L.; Assumpção, G. G. T.; Ji, Y.; Chen, J.; Knap, M.; Navon, N. The strongly driven Fermi polaron Journal Article Nat. Phys. 21, 564 (2025). @article{vivanco_strongly_2025,
title = {The strongly driven Fermi polaron},
author = {F. J. Vivanco and A. Schuckert and S. Huang and G. L. Schumacher and G. G. T. Assumpção and Y. Ji and J. Chen and M. Knap and N. Navon},
url = {https://doi.org/10.1038/s41567-025-02799-8},
doi = {10.1038/s41567-025-02799-8},
year = {2025},
date = {2025-04-01},
urldate = {2023-01-01},
journal = {Nat. Phys.},
volume = {21},
number = {4},
pages = {564},
abstract = {Quasiparticles are emergent excitations of matter that underlie much of our understanding of quantum many-body systems. Therefore, the prospect of controlling their properties has both fundamental and practical implications. However, in solid-state materials, it is often challenging to understand how quasiparticles are modified by external fields due to their complex interplay with other collective excitations. Here we demonstrate the manipulation of Fermi polarons—quasiparticles formed by impurities interacting with a Fermi gas—in a homogeneous atomic gas using fast radio-frequency control. Exploiting two internal states of the impurity species, we develop a steady-state spectroscopy, from which we extract the energy of the driven polaron. By varying the drive Rabi frequency, we measure the decay rate and the quasiparticle residue of the polaron in the weak-drive limit. At large Rabi frequencies, we observe signs that the drive causes a hybridization of the driven polaron with an incoherent background, leading to the breakdown of a description in terms of textbook quasiparticles. Our experiment establishes the driven Fermi polaron as a promising platform for studying controllable quasiparticles in strongly driven quantum matter and calls for a controlled theoretical framework to describe the dynamics of this strongly interacting quantum system.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quasiparticles are emergent excitations of matter that underlie much of our understanding of quantum many-body systems. Therefore, the prospect of controlling their properties has both fundamental and practical implications. However, in solid-state materials, it is often challenging to understand how quasiparticles are modified by external fields due to their complex interplay with other collective excitations. Here we demonstrate the manipulation of Fermi polarons—quasiparticles formed by impurities interacting with a Fermi gas—in a homogeneous atomic gas using fast radio-frequency control. Exploiting two internal states of the impurity species, we develop a steady-state spectroscopy, from which we extract the energy of the driven polaron. By varying the drive Rabi frequency, we measure the decay rate and the quasiparticle residue of the polaron in the weak-drive limit. At large Rabi frequencies, we observe signs that the drive causes a hybridization of the driven polaron with an incoherent background, leading to the breakdown of a description in terms of textbook quasiparticles. Our experiment establishes the driven Fermi polaron as a promising platform for studying controllable quasiparticles in strongly driven quantum matter and calls for a controlled theoretical framework to describe the dynamics of this strongly interacting quantum system. | |
Uykur, E.; Janson, O.; Ginga, V. A.; Schmidt, M.; Giordano, N.; Tsirlin, A. A. Tunable Dirac nodal line in orthorhombic RuO2 Journal Article Phys. Rev. B 111, 134114 (2025). @article{uykur_tunable_2025,
title = {Tunable Dirac nodal line in orthorhombic RuO_{2}},
author = {E. Uykur and O. Janson and V. A. Ginga and M. Schmidt and N. Giordano and A. A. Tsirlin},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.134114},
doi = {10.1103/PhysRevB.111.134114},
year = {2025},
date = {2025-04-01},
urldate = {2025-04-01},
journal = {Phys. Rev. B},
volume = {111},
number = {13},
pages = {134114},
abstract = {The pressure evolution of RuO2 is studied using single-crystal x-ray diffraction in a diamond anvil cell, combined with ab initio band-structure calculations. The tetragonal rutile structure transforms into the orthorhombic CaCl2-type structure above 13 GPa under quasihydrostatic pressure conditions. This second-order transition is ferroelastic in nature and accompanied by tilts of the RuO6 octahedra. Orthorhombic RuO2 is expected to be a paramagnetic metal, similar to ambient-pressure RuO2. It shows the increased 𝑡2𝑔−𝑒𝑔 crystal-field splitting that is responsible for the pressure-induced color change. It further features the Dirac nodal line that shifts across the Fermi level upon compression.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
The pressure evolution of RuO2 is studied using single-crystal x-ray diffraction in a diamond anvil cell, combined with ab initio band-structure calculations. The tetragonal rutile structure transforms into the orthorhombic CaCl2-type structure above 13 GPa under quasihydrostatic pressure conditions. This second-order transition is ferroelastic in nature and accompanied by tilts of the RuO6 octahedra. Orthorhombic RuO2 is expected to be a paramagnetic metal, similar to ambient-pressure RuO2. It shows the increased 𝑡2𝑔−𝑒𝑔 crystal-field splitting that is responsible for the pressure-induced color change. It further features the Dirac nodal line that shifts across the Fermi level upon compression. | |
Halloran, T.; Wang, Y.; Plumb, K. W.; Stone, M. B.; Winn, B.; Graves-Brook, M. K.; Rodriguez-Rivera, J. A.; Qui, Y.; Chauhan, P.; Knolle, J.; Moessner, R.; Armitage, N. P.; Takayama, T.; Takagi, H.; Broholm, C. Continuum of magnetic excitations in the Kitaev honeycomb iridate D3LiIr2O6 Journal Article npj Quantum Mater. 10, 35 (2025). @article{halloran_continuum_2025,
title = {Continuum of magnetic excitations in the Kitaev honeycomb iridate D_{3}LiIr_{2}O_{6}},
author = {T. Halloran and Y. Wang and K. W. Plumb and M. B. Stone and B. Winn and M. K. Graves-Brook and J. A. Rodriguez-Rivera and Y. Qui and P. Chauhan and J. Knolle and R. Moessner and N. P. Armitage and T. Takayama and H. Takagi and C. Broholm},
url = {https://www.nature.com/articles/s41535-025-00748-5},
doi = {10.1038/s41535-025-00748-5},
year = {2025},
date = {2025-03-29},
urldate = {2025-03-29},
journal = {npj Quantum Mater.},
volume = {10},
pages = {35},
abstract = {Inelastic neutron scattering (INS) measurements of powder D3LiIr2O6 reveal low energy magnetic excitations with a scattering cross-section that is broad in ∣Q∣ and energy transfer. The magnetic nature of the excitation spectrum is demonstrated by longitudinally polarized neutron scattering. The total magnetic moment of 1.8(4)μB/Ir inferred from the observed magnetic scattering cross-section is consistent with the effective moment inferred from magnetic susceptibility data and expectations for the Jeff = 1/2 single ion state. The rise in the dynamic correlation function S(Q, ω) for ℏω < 5 meV can be described by a simple model assuming nearest-neighbor anisotropic spin exchange, such as that found in the Kitaev model. Exchange disorder associated with the D site likely plays an important role in stabilizing the low T quantum fluctuating state.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Inelastic neutron scattering (INS) measurements of powder D3LiIr2O6 reveal low energy magnetic excitations with a scattering cross-section that is broad in ∣Q∣ and energy transfer. The magnetic nature of the excitation spectrum is demonstrated by longitudinally polarized neutron scattering. The total magnetic moment of 1.8(4)μB/Ir inferred from the observed magnetic scattering cross-section is consistent with the effective moment inferred from magnetic susceptibility data and expectations for the Jeff = 1/2 single ion state. The rise in the dynamic correlation function S(Q, ω) for ℏω < 5 meV can be described by a simple model assuming nearest-neighbor anisotropic spin exchange, such as that found in the Kitaev model. Exchange disorder associated with the D site likely plays an important role in stabilizing the low T quantum fluctuating state. | |
Que, X.; He, Q.; Zhou, L.; Lei, S.; Schoop, L.; Huang, D.; Takagi, H. Visualizing the internal structure of the charge-density-wave state in CeSbTe Journal Article Nat. Commun. 16, 3053 (2025). @article{que_visualizing_2025,
title = {Visualizing the internal structure of the charge-density-wave state in CeSbTe},
author = {X. Que and Q. He and L. Zhou and S. Lei and L. Schoop and D. Huang and H. Takagi},
url = {https://doi.org/10.1038/s41467-025-58417-x},
doi = {10.1038/s41467-025-58417-x},
year = {2025},
date = {2025-03-28},
urldate = {2025-03-01},
journal = {Nat. Commun.},
volume = {16},
number = {1},
pages = {3053},
abstract = {The collective reorganization of electrons into a charge density wave has long served as a textbook example of an ordered phase in condensed matter physics. Two-dimensional square lattices with p electrons are well-suited to the realization of charge density waves, due to the anisotropy of the p orbitals and the resulting one dimensionality of the electronic structure. In spite of a long history of study of charge density waves in square-lattice systems, few reports have recognized the significance of a hidden orbital degree of freedom. The degeneracy of px and py electrons may give rise to orbital patterns in real space that endow the charge density wave with additional broken symmetries or unusual order parameters. Here, we use scanning tunneling microscopy to visualize the internal structure of the charge-density-wave state of CeSbTe, which contains Sb square lattices with 5p electrons. We image atomic-sized, anisotropic lobes of charge density with periodically modulating anisotropy, which we interpret in terms of a superposition of px and py bond density waves. Our results support the fact that delocalized p orbitals can reorganize into emergent electronic states of matter.},
keywords = {A3},
pubstate = {published},
tppubtype = {article}
}
The collective reorganization of electrons into a charge density wave has long served as a textbook example of an ordered phase in condensed matter physics. Two-dimensional square lattices with p electrons are well-suited to the realization of charge density waves, due to the anisotropy of the p orbitals and the resulting one dimensionality of the electronic structure. In spite of a long history of study of charge density waves in square-lattice systems, few reports have recognized the significance of a hidden orbital degree of freedom. The degeneracy of px and py electrons may give rise to orbital patterns in real space that endow the charge density wave with additional broken symmetries or unusual order parameters. Here, we use scanning tunneling microscopy to visualize the internal structure of the charge-density-wave state of CeSbTe, which contains Sb square lattices with 5p electrons. We image atomic-sized, anisotropic lobes of charge density with periodically modulating anisotropy, which we interpret in terms of a superposition of px and py bond density waves. Our results support the fact that delocalized p orbitals can reorganize into emergent electronic states of matter. | |
Hayashida, S.; Gretarsson, H.; Puphal, P.; Isobe, M.; Goering, E.; Matsumoto, Y.; Nuss, J.; Takagi, H.; Hepting, M.; Keimer, B. Magnetic ground state of the dimer-based hexagonal perovskite Ba3ZnRu2O9 Journal Article Phys. Rev. B 111, 104418 (2025). @article{hayashida_magnetic_2025,
title = {Magnetic ground state of the dimer-based hexagonal perovskite Ba_{3}ZnRu_{2}O_{9}},
author = {S. Hayashida and H. Gretarsson and P. Puphal and M. Isobe and E. Goering and Y. Matsumoto and J. Nuss and H. Takagi and M. Hepting and B. Keimer},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.104418},
doi = {10.1103/PhysRevB.111.104418},
year = {2025},
date = {2025-03-13},
urldate = {2025-03-01},
journal = {Phys. Rev. B},
volume = {111},
number = {10},
pages = {104418},
abstract = {We investigate the magnetic ground state of single crystals of the ruthenium-dimer-based hexagonal perovskite Ba3ZnRu2O9 using magnetic susceptibility and resonant inelastic x-ray scattering (RIXS) measurements. While a previous study on powder samples exhibited intriguing magnetic behavior, questions about whether the spin state within a Ru2O9 dimer is a conventional 𝑆=3/2 dimer or an orbital-selective 𝑆=1 dimer were raised. The RIXS spectra reveal magnetic excitations from Hund's intraionic multiplet and intradimer spin-triplet transitions. The observed transition energies of the Hund's intraionic multiplets align with the 𝑆=3/2 ground state, contrasting with the theoretically proposed orbital-selective 𝑆=1 dimer state. High-temperature magnetic susceptibility analysis confirms the realization of the spin 𝑆=3/2 dimer state, and the extracted intradimer coupling is consistent with the spin-triplet transition energy observed in the RIXS spectra. These results highlights the ability of “spectroscopic fingerprinting” by RIXS to determine the magnetic ground states of complex materials.},
keywords = {B2},
pubstate = {published},
tppubtype = {article}
}
We investigate the magnetic ground state of single crystals of the ruthenium-dimer-based hexagonal perovskite Ba3ZnRu2O9 using magnetic susceptibility and resonant inelastic x-ray scattering (RIXS) measurements. While a previous study on powder samples exhibited intriguing magnetic behavior, questions about whether the spin state within a Ru2O9 dimer is a conventional 𝑆=3/2 dimer or an orbital-selective 𝑆=1 dimer were raised. The RIXS spectra reveal magnetic excitations from Hund's intraionic multiplet and intradimer spin-triplet transitions. The observed transition energies of the Hund's intraionic multiplets align with the 𝑆=3/2 ground state, contrasting with the theoretically proposed orbital-selective 𝑆=1 dimer state. High-temperature magnetic susceptibility analysis confirms the realization of the spin 𝑆=3/2 dimer state, and the extracted intradimer coupling is consistent with the spin-triplet transition energy observed in the RIXS spectra. These results highlights the ability of “spectroscopic fingerprinting” by RIXS to determine the magnetic ground states of complex materials. | |
Telang, P.; Treu, T.; Klinger, M.; Tsirlin, A. A.; Gegenwart, P.; Jesche, A. Adiabatic demagnetization refrigeration with antiferromagnetically ordered NaGdP2O7 Journal Article Phys. Rev. B 111, 064431 (2025). @article{telang_adiabatic_2025,
title = {Adiabatic demagnetization refrigeration with antiferromagnetically ordered NaGdP_{2}O_{7}},
author = {P. Telang and T. Treu and M. Klinger and A. A. Tsirlin and P. Gegenwart and A. Jesche},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.064431},
doi = {10.1103/PhysRevB.111.064431},
year = {2025},
date = {2025-02-28},
urldate = {2025-02-01},
journal = {Phys. Rev. B},
volume = {111},
number = {6},
pages = {064431},
keywords = {B3},
pubstate = {published},
tppubtype = {article}
}
| |
Leeb, V.; Huber, N.; Pfleiderer, C.; Knolle, J.; Wilde, M. A. A Field Guide to Non-Onsager Quantum Oscillations in Metals Journal Article Adv. Phys. Res. 4, 2400134 (2025). @article{leeb_field_2025,
title = {A Field Guide to Non-Onsager Quantum Oscillations in Metals},
author = {V. Leeb and N. Huber and C. Pfleiderer and J. Knolle and M. A. Wilde},
url = {https://doi.org/10.1002/apxr.202400134},
doi = {10.1002/apxr.202400134},
year = {2025},
date = {2025-02-25},
urldate = {2025-02-28},
journal = {Adv. Phys. Res.},
volume = {4},
number = {4},
pages = {2400134},
abstract = {Abstract Quantum oscillation (QO) measurements constitute a powerful method to measure the Fermi surface (FS) properties of metals. The observation of QOs is usually taken as strong evidence for the existence of extremal cross-sectional areas of the FS according to the famous Onsager relation. Here, mechanisms that generate QO frequencies that defy the Onsager relation are reviewed and material candidates are discussed. These include magnetic breakdown, magnetic interaction, chemical potential oscillations, and Stark quantum interference, most of which lead to signals occurring at combinations of ?parent? Onsager frequencies. A special emphasis is put on the recently discovered mechanism of quasi-particle lifetime oscillations (QPLOs). This work aims to provide a field guide that allows, on the one hand, to distinguish such non-Onsager QOs from conventional QOs arising from extremal cross sections and, on the other hand, to distinguish the various non-Onsager mechanisms from each other. A practical classification of non-Onsager QOs is given in terms of the prerequisites for their occurrence and their characteristics. It is shown that, in particular, the recently discovered QPLOs may pose significant challenges for the interpretation of QO spectra, as they may occur quite generically as frequency differences in multi-orbit systems, without the necessity of visible ?parent? frequencies in the spectrum, owing to a strongly suppressed temperature dephasing of QPLOs. An extensive list of material candidates is presented where QPLOs may represent an alternative explanation for the observation of unexpected QO frequencies.},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
Abstract Quantum oscillation (QO) measurements constitute a powerful method to measure the Fermi surface (FS) properties of metals. The observation of QOs is usually taken as strong evidence for the existence of extremal cross-sectional areas of the FS according to the famous Onsager relation. Here, mechanisms that generate QO frequencies that defy the Onsager relation are reviewed and material candidates are discussed. These include magnetic breakdown, magnetic interaction, chemical potential oscillations, and Stark quantum interference, most of which lead to signals occurring at combinations of ?parent? Onsager frequencies. A special emphasis is put on the recently discovered mechanism of quasi-particle lifetime oscillations (QPLOs). This work aims to provide a field guide that allows, on the one hand, to distinguish such non-Onsager QOs from conventional QOs arising from extremal cross sections and, on the other hand, to distinguish the various non-Onsager mechanisms from each other. A practical classification of non-Onsager QOs is given in terms of the prerequisites for their occurrence and their characteristics. It is shown that, in particular, the recently discovered QPLOs may pose significant challenges for the interpretation of QO spectra, as they may occur quite generically as frequency differences in multi-orbit systems, without the necessity of visible ?parent? frequencies in the spectrum, owing to a strongly suppressed temperature dephasing of QPLOs. An extensive list of material candidates is presented where QPLOs may represent an alternative explanation for the observation of unexpected QO frequencies. | |
Kong, D.; Kovács, A.; Charilaou, M.; Altthaler, M.; Prodan, L.; Tsurkan, V.; Meier, D.; Han, X.; Kézsmárki, I.; Dunin-Borkowski, R. E. Strain Engineering of Magnetic Anisotropy in the Kagome Magnet Fe3Sn2 Journal Article ACS Nano 19, 8142–8151 (2025). @article{kong_strain_2025,
title = {Strain Engineering of Magnetic Anisotropy in the Kagome Magnet Fe_{3}Sn_{2}},
author = {D. Kong and A. Kovács and M. Charilaou and M. Altthaler and L. Prodan and V. Tsurkan and D. Meier and X. Han and I. Kézsmárki and R. E. Dunin-Borkowski},
url = {https://doi.org/10.1021/acsnano.4c16603},
doi = {10.1021/acsnano.4c16603},
year = {2025},
date = {2025-02-24},
urldate = {2025-03-01},
journal = {ACS Nano},
volume = {19},
number = {8},
pages = {8142–8151},
abstract = {The ability to control magnetism with strain offers innovative pathways for the modulation of magnetic domain configurations and for the manipulation of magnetic states in materials on the nanoscale. Although the effect of strain on magnetic domains has been recognized since the early work of C. Kittel, detailed local observations have been elusive. Here, we use mechanical strain to achieve reversible control of magnetic textures in a kagome-type Fe3Sn2 ferromagnet without the use of an external electric current or magnetic field in situ in a transmission electron microscope at room temperature. We use Fresnel defocus imaging, off-axis electron holography and micromagnetic simulations to show that tensile strain modifies the structures of dipolar skyrmions and switches the magnetization between out-of-plane and in-plane configurations. We also present quantitative measurements of magnetic domain wall structures and their transformations as a function of strain. Our results demonstrate the fundamental importance of anisotropy effects and their interplay with magnetoelastic and magnetocrystalline energies, providing opportunities for the development of strain-controlled devices for spintronic applications.},
keywords = {A4},
pubstate = {published},
tppubtype = {article}
}
The ability to control magnetism with strain offers innovative pathways for the modulation of magnetic domain configurations and for the manipulation of magnetic states in materials on the nanoscale. Although the effect of strain on magnetic domains has been recognized since the early work of C. Kittel, detailed local observations have been elusive. Here, we use mechanical strain to achieve reversible control of magnetic textures in a kagome-type Fe3Sn2 ferromagnet without the use of an external electric current or magnetic field in situ in a transmission electron microscope at room temperature. We use Fresnel defocus imaging, off-axis electron holography and micromagnetic simulations to show that tensile strain modifies the structures of dipolar skyrmions and switches the magnetization between out-of-plane and in-plane configurations. We also present quantitative measurements of magnetic domain wall structures and their transformations as a function of strain. Our results demonstrate the fundamental importance of anisotropy effects and their interplay with magnetoelastic and magnetocrystalline energies, providing opportunities for the development of strain-controlled devices for spintronic applications. | |
Zahn, M.; Müller, A. M.; Kelley, K. P.; Neumayer, S.; Kalinin, S. V.; Kézsmarki, I.; Fiebig, M.; Lottermoser, T.; Domingo, N.; Meier, D.; Schultheiß, J. Reversible long-range domain wall motion in an improper ferroelectric Journal Article Nat. Commun. 16, 1781 (2025). @article{zahn_reversible_2025,
title = {Reversible long-range domain wall motion in an improper ferroelectric},
author = {M. Zahn and A. M. Müller and K. P. Kelley and S. Neumayer and S. V. Kalinin and I. Kézsmarki and M. Fiebig and T. Lottermoser and N. Domingo and D. Meier and J. Schultheiß},
url = {https://doi.org/10.1038/s41467-025-57062-8},
doi = {10.1038/s41467-025-57062-8},
year = {2025},
date = {2025-02-19},
urldate = {2025-02-19},
journal = {Nat. Commun.},
volume = {16},
number = {1},
pages = {1781},
abstract = {Reversible ferroelectric domain wall movements beyond the 10 nm range associated with Rayleigh behavior are usually restricted to specific defect-engineered systems. Here, we demonstrate that such long-range movements naturally occur in the improper ferroelectric ErMnO3 during electric-field-cycling. We study the electric-field-driven motion of domain walls, showing that they readily return to their initial position after having traveled distances exceeding 250 nm. By applying switching spectroscopy band-excitation piezoresponse force microscopy, we track the domain wall movement with nanometric spatial precision and analyze the local switching behavior. Phase field simulations show that the reversible long-range motion is intrinsic to the hexagonal manganites, linking it to their improper ferroelectricity and topologically protected structural vortex lines, which serve as anchor point for the ferroelectric domain walls. Our results give new insight into the local dynamics of domain walls in improper ferroelectrics and demonstrate the possibility to reversibly displace domain walls over much larger distances than commonly expected for ferroelectric systems in their pristine state, ensuring predictable device behavior for applications such as tunable capacitors or sensors.},
keywords = {A4},
pubstate = {published},
tppubtype = {article}
}
Reversible ferroelectric domain wall movements beyond the 10 nm range associated with Rayleigh behavior are usually restricted to specific defect-engineered systems. Here, we demonstrate that such long-range movements naturally occur in the improper ferroelectric ErMnO3 during electric-field-cycling. We study the electric-field-driven motion of domain walls, showing that they readily return to their initial position after having traveled distances exceeding 250 nm. By applying switching spectroscopy band-excitation piezoresponse force microscopy, we track the domain wall movement with nanometric spatial precision and analyze the local switching behavior. Phase field simulations show that the reversible long-range motion is intrinsic to the hexagonal manganites, linking it to their improper ferroelectricity and topologically protected structural vortex lines, which serve as anchor point for the ferroelectric domain walls. Our results give new insight into the local dynamics of domain walls in improper ferroelectrics and demonstrate the possibility to reversibly displace domain walls over much larger distances than commonly expected for ferroelectric systems in their pristine state, ensuring predictable device behavior for applications such as tunable capacitors or sensors. | |
Wenzel, M.; Uykur, E.; Rößler, S.; Schmidt, M.; Janson, O.; Tiwari, A.; Dressel, M.; Tsirlin, A. A. Fermi-liquid behavior of nonaltermagnetic RuO2 Journal Article Phys. Rev. B 111, L041115 (2025). @article{wenzel_fermi-liquid_2025,
title = {Fermi-liquid behavior of nonaltermagnetic RuO_{2}},
author = {M. Wenzel and E. Uykur and S. Rößler and M. Schmidt and O. Janson and A. Tiwari and M. Dressel and A. A. Tsirlin},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.L041115},
doi = {10.1103/PhysRevB.111.L041115},
year = {2025},
date = {2025-01-28},
urldate = {2025-01-28},
journal = {Phys. Rev. B},
volume = {111},
number = {4},
pages = {L041115},
abstract = {The presence of magnetism in potentially altermagnetic RuO2 has been a subject of intense debate. Using broadband infrared spectroscopy combined with density-functional band-structure calculations, we show that the optical conductivity of RuO2, the bulk probe of its electronic structure, is best described by a nonmagnetic model. The sharp Pauli edge demonstrates the presence of a Dirac nodal line lying 45 meV below the Fermi level. An excellent match between the experimental and ab initio plasma frequencies underpins the weakness of electronic correlations. The intraband part of the optical conductivity indicates Fermi-liquid behavior with two distinct scattering rates below 150 K. Fermi-liquid theory also accounts for the temperature-dependent magnetic susceptibility of RuO2 and allows a consistent description of this material as a paramagnetic metal.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
The presence of magnetism in potentially altermagnetic RuO2 has been a subject of intense debate. Using broadband infrared spectroscopy combined with density-functional band-structure calculations, we show that the optical conductivity of RuO2, the bulk probe of its electronic structure, is best described by a nonmagnetic model. The sharp Pauli edge demonstrates the presence of a Dirac nodal line lying 45 meV below the Fermi level. An excellent match between the experimental and ab initio plasma frequencies underpins the weakness of electronic correlations. The intraband part of the optical conductivity indicates Fermi-liquid behavior with two distinct scattering rates below 150 K. Fermi-liquid theory also accounts for the temperature-dependent magnetic susceptibility of RuO2 and allows a consistent description of this material as a paramagnetic metal. | |
Shen, B.; Insuasti Pazmino, E.; Dhakal, R.; Freund, F.; Gegenwart, P.; Winter, S. M.; Tsirlin, A. A. Pressure-dependent magnetism of the Kitaev candidate Li2RhO3 Journal Article npj Quantum Mater. 10, 9 (2025). @article{shen_pressure-dependent_2025,
title = {Pressure-dependent magnetism of the Kitaev candidate Li_{2}RhO_{3}},
author = {B. Shen and Insuasti Pazmino, E. and R. Dhakal and F. Freund and P. Gegenwart and S. M. Winter and A. A. Tsirlin},
url = {https://doi.org/10.1038/s41535-025-00730-1},
doi = {10.1038/s41535-025-00730-1},
year = {2025},
date = {2025-01-22},
urldate = {2025-01-22},
journal = {npj Quantum Mater.},
volume = {10},
number = {1},
pages = {9},
abstract = {We use magnetization measurements under pressure along with ab initio and cluster many-body calculations to investigate magnetism of the Kitaev candidate Li2RhO3. Hydrostatic compression leads to a decrease in the magnitude of the nearest-neighbor ferromagnetic Kitaev coupling K1 and the corresponding increase in the off-diagonal anisotropy Γ1, whereas the experimental Curie-Weiss temperature changes from negative to positive with the slope of +40 K/GPa. On the other hand, spin freezing persists up to at least 3.46 GPa with the almost constant freezing temperature of 5 K that does not follow the large changes in the exchange couplings and indicates the likely extrinsic origin of spin freezing. Magnetic frustration in Li2RhO3 is mainly related to the interplay between ferromagnetic K1 and antiferromagnetic Γ1, along with the weakness of the third-neighbor coupling J3 that would otherwise stabilize zigzag order. The small J3 distinguishes Li2RhO3 from other Kitaev candidates.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
We use magnetization measurements under pressure along with ab initio and cluster many-body calculations to investigate magnetism of the Kitaev candidate Li2RhO3. Hydrostatic compression leads to a decrease in the magnitude of the nearest-neighbor ferromagnetic Kitaev coupling K1 and the corresponding increase in the off-diagonal anisotropy Γ1, whereas the experimental Curie-Weiss temperature changes from negative to positive with the slope of +40 K/GPa. On the other hand, spin freezing persists up to at least 3.46 GPa with the almost constant freezing temperature of 5 K that does not follow the large changes in the exchange couplings and indicates the likely extrinsic origin of spin freezing. Magnetic frustration in Li2RhO3 is mainly related to the interplay between ferromagnetic K1 and antiferromagnetic Γ1, along with the weakness of the third-neighbor coupling J3 that would otherwise stabilize zigzag order. The small J3 distinguishes Li2RhO3 from other Kitaev candidates. | |
Papaefstathiou, I.; Knolle, J.; Bañuls, M. C. Real-time scattering in the lattice Schwinger model Journal Article Phys. Rev. D 111, 014504 (2025). @article{papaefstathiou_real-time_2025,
title = {Real-time scattering in the lattice Schwinger model},
author = {I. Papaefstathiou and J. Knolle and M. C. Bañuls},
url = {https://link.aps.org/doi/10.1103/PhysRevD.111.014504},
doi = {10.1103/PhysRevD.111.014504},
year = {2025},
date = {2025-01-15},
urldate = {2025-01-15},
journal = {Phys. Rev. D},
volume = {111},
number = {1},
pages = {014504},
keywords = {C5, C6},
pubstate = {published},
tppubtype = {article}
}
| |
Xu, W. -T.; Rakovszky, T.; Knap, M.; Pollmann, F. Entanglement Properties of Gauge Theories from Higher-Form Symmetries Journal Article Phys. Rev. X 15, 011001 (2025). @article{xu_entanglement_2025,
title = {Entanglement Properties of Gauge Theories from Higher-Form Symmetries},
author = {W. -T. Xu and T. Rakovszky and M. Knap and F. Pollmann},
doi = {10.1103/PhysRevX.15.011001},
year = {2025},
date = {2025-01-02},
urldate = {2025-01-01},
journal = {Phys. Rev. X},
volume = {15},
number = {1},
pages = {011001},
abstract = {We explore the relationship between higher-form symmetries and entanglement properties in lattice gauge theories with discrete gauge groups, which can exhibit both topologically ordered phases and higher-form symmetry-protected topological (SPT) phases. Our study centers on a generalization of the Fradkin-Shenker model describing ℤ2 lattice gauge theory with matter, where the Gauss law constraint can be either emergent or exact. The phase diagram includes a topologically ordered deconfined phase and a nontrivial SPT phase protected by a 1-form and a 0-form symmetry, among others. We obtain the following key findings: First, the entanglement properties of the model depend on whether the 1-form symmetries and the Gauss law constraint are exact or emergent. For the emergent Gauss law, the entanglement spectrum (ES) of the nontrivial SPT phase exhibits degeneracies, which are robust at low energies against weak perturbations that explicitly break the exact 1-form symmetry. When the Gauss law and the 1-form symmetry are both exact, the ES degeneracy is extensive. This extensive degeneracy turns out to be fragile and can be removed completely by infinitesimal perturbations that explicitly break the exact 1-form symmetry while keeping the Gauss law exact. Second, we consider the ES in the topologically ordered phase where 1-form symmetries are spontaneously broken. In contrast to the ES of the nontrivial SPT phase, we find that spontaneous higher-form symmetry breaking removes “half” of the ES levels, leading to a nondegenerate ES in the topologically ordered phase, in general. Third, we derive a connection between spontaneous higher-form symmetry breaking and the topological entanglement entropy (TEE). Using this relation, we investigate the entanglement entropy that can be distilled in the deconfined phase of the original Fradkin-Shenker model using gauge-invariant measurements. We show that the TEE is robust against the measurement when the 1-form symmetry is emergent but it is fragile when the 1-form symmetry is exact. Our results demonstrate the advantage of higher-form symmetries for understanding entanglement properties of gauge theories.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We explore the relationship between higher-form symmetries and entanglement properties in lattice gauge theories with discrete gauge groups, which can exhibit both topologically ordered phases and higher-form symmetry-protected topological (SPT) phases. Our study centers on a generalization of the Fradkin-Shenker model describing ℤ2 lattice gauge theory with matter, where the Gauss law constraint can be either emergent or exact. The phase diagram includes a topologically ordered deconfined phase and a nontrivial SPT phase protected by a 1-form and a 0-form symmetry, among others. We obtain the following key findings: First, the entanglement properties of the model depend on whether the 1-form symmetries and the Gauss law constraint are exact or emergent. For the emergent Gauss law, the entanglement spectrum (ES) of the nontrivial SPT phase exhibits degeneracies, which are robust at low energies against weak perturbations that explicitly break the exact 1-form symmetry. When the Gauss law and the 1-form symmetry are both exact, the ES degeneracy is extensive. This extensive degeneracy turns out to be fragile and can be removed completely by infinitesimal perturbations that explicitly break the exact 1-form symmetry while keeping the Gauss law exact. Second, we consider the ES in the topologically ordered phase where 1-form symmetries are spontaneously broken. In contrast to the ES of the nontrivial SPT phase, we find that spontaneous higher-form symmetry breaking removes “half” of the ES levels, leading to a nondegenerate ES in the topologically ordered phase, in general. Third, we derive a connection between spontaneous higher-form symmetry breaking and the topological entanglement entropy (TEE). Using this relation, we investigate the entanglement entropy that can be distilled in the deconfined phase of the original Fradkin-Shenker model using gauge-invariant measurements. We show that the TEE is robust against the measurement when the 1-form symmetry is emergent but it is fragile when the 1-form symmetry is exact. Our results demonstrate the advantage of higher-form symmetries for understanding entanglement properties of gauge theories. | |
Shiotani, T.; Waki, T.; Tabata, Y.; Kézsmárki, I.; Nakamura, H. Novel family of near-room-temperature compensated itinerant pyrochlore ferrimagnets, RInCo4 (R = Dy-Tm) Unpublished (2025), arXiv:2510.04287. @unpublished{shiotani_novel_2025,
title = {Novel family of near-room-temperature compensated itinerant pyrochlore ferrimagnets, RInCo_{4} (R = Dy-Tm)},
author = {T. Shiotani and T. Waki and Y. Tabata and I. Kézsmárki and H. Nakamura},
url = {https://arxiv.org/abs/2510.04287},
doi = {10.48550/arXiv.2510.04287},
year = {2025},
date = {2025-10-05},
urldate = {2025-10-05},
abstract = {We successfully synthesized single crystals of a series of C15b Laves phase compounds, RInCo4 (R=Dy-Tm), with Co-pyrochlore and R-fcc sublattices, and systematically studied their magnetic properties via magnetometry measurements. These itinerant cubic compounds, with Curie temperatures above room temperature, show compensated ferrimagnetism featuring an antiferromagnetic coupling between the two sublattices. From this series, DyInCo4 exhibits the highest T_C (= 368 K) and a near-room-temperature compensation point T_cp (= 295 K). T_C does not change drastically with the R atom, whereas T_cp depends on the de Gennes factor of R^3+. Another magnetization anomaly is observed in all the compounds at low temperatures, which may be indicative of changes in the lattice or magnetic structure. The easy axis the ferrimagnetic moment of DyInCo4, ErInCo4, and TmInCo4 is found at T = 5 K to be along the [001], [111] and [110] directions, respectively. However, the simple easy-axis or easy-plane ferrimagnetic picture cannot be applied to HoInCo4. These observations suggest that the R sublattice determines magnetic anisotropy and compensation, while the Co sublattice plays a role in strong magnetic ordering. The high Curie temperature, together with the magnetization compensation point near room temperature, renders these itinerant pyrochlore magnets interesting for spintronic applications. },
note = {arXiv:2510.04287},
keywords = {A4},
pubstate = {published},
tppubtype = {unpublished}
}
We successfully synthesized single crystals of a series of C15b Laves phase compounds, RInCo4 (R=Dy-Tm), with Co-pyrochlore and R-fcc sublattices, and systematically studied their magnetic properties via magnetometry measurements. These itinerant cubic compounds, with Curie temperatures above room temperature, show compensated ferrimagnetism featuring an antiferromagnetic coupling between the two sublattices. From this series, DyInCo4 exhibits the highest T_C (= 368 K) and a near-room-temperature compensation point T_cp (= 295 K). T_C does not change drastically with the R atom, whereas T_cp depends on the de Gennes factor of R^3+. Another magnetization anomaly is observed in all the compounds at low temperatures, which may be indicative of changes in the lattice or magnetic structure. The easy axis the ferrimagnetic moment of DyInCo4, ErInCo4, and TmInCo4 is found at T = 5 K to be along the [001], [111] and [110] directions, respectively. However, the simple easy-axis or easy-plane ferrimagnetic picture cannot be applied to HoInCo4. These observations suggest that the R sublattice determines magnetic anisotropy and compensation, while the Co sublattice plays a role in strong magnetic ordering. The high Curie temperature, together with the magnetization compensation point near room temperature, renders these itinerant pyrochlore magnets interesting for spintronic applications. | |
Tang, N.; Glamsch, S.; Aqeel, A.; Scheuchenpflug, L.; Schulze, M.; Liebald, C.; Rytz, D.; Guguschev, C.; Albrecht, M.; Gegenwart, P. Observation via spin Seebeck effect of macroscopic magnetic transport from emergent magnetic monopoles Unpublished (2025), arXiv:2509.18422. @unpublished{tang_observation_2025,
title = {Observation via spin Seebeck effect of macroscopic magnetic transport from emergent magnetic monopoles},
author = {N. Tang and S. Glamsch and A. Aqeel and L. Scheuchenpflug and M. Schulze and C. Liebald and D. Rytz and C. Guguschev and M. Albrecht and P. Gegenwart},
url = {https://arxiv.org/abs/2509.18422},
doi = {10.48550/arXiv.2509.18422},
year = {2025},
date = {2025-09-22},
urldate = {2025-09-22},
abstract = {Magnetic monopoles, elusive in high-energy physics, have been realised as emergent quasiparticles in solid-state systems, where their unique properties hold promise for novel spintronic applications. Magnetic monopoles have been invoked in diverse platforms, including skyrmion lattices, chiral magnets, soft ferromagnets, aritifical nanomagnets. Yet, a demonstration of their role in magnetic transport has remained elusive. Here, we report such an observation via the spin Seebeck effect in the bulk insulating pyrochlore oxide, spin ice Dy2Ti2O7. By applying a thermal gradient perpendicular to a [111]-oriented magnetic field, we detect a transverse spin Seebeck voltage marked by a dominant peak at the onset of monopole proliferation, accompanied by a secondary feature and frequency-dependent behavior. Our findings establish a direct link between monopole dynamics and magnetic transport in an insulating medium, establishing a new pathway for probing fractionalized excitations and advancing towards novel spintronic applications.},
note = {arXiv:2509.18422},
keywords = {A2, B5},
pubstate = {published},
tppubtype = {unpublished}
}
Magnetic monopoles, elusive in high-energy physics, have been realised as emergent quasiparticles in solid-state systems, where their unique properties hold promise for novel spintronic applications. Magnetic monopoles have been invoked in diverse platforms, including skyrmion lattices, chiral magnets, soft ferromagnets, aritifical nanomagnets. Yet, a demonstration of their role in magnetic transport has remained elusive. Here, we report such an observation via the spin Seebeck effect in the bulk insulating pyrochlore oxide, spin ice Dy2Ti2O7. By applying a thermal gradient perpendicular to a [111]-oriented magnetic field, we detect a transverse spin Seebeck voltage marked by a dominant peak at the onset of monopole proliferation, accompanied by a secondary feature and frequency-dependent behavior. Our findings establish a direct link between monopole dynamics and magnetic transport in an insulating medium, establishing a new pathway for probing fractionalized excitations and advancing towards novel spintronic applications. | |
Nandi, S.; Das, R.; Mahapatra, S.; Sichelschmidt, J.; Hemmida, M.; von Nidda, H. -A. Krug; Schuller, M.; Büttgen, N.; Wilkinson, J.; Saravanan, M. P.; Dasgupta, I.; Mahajan, A. V. Novel Quantum Spin Liquid states in the S = 1/2 three-dimensional compound Y3Cu2Sb3O14 Unpublished (2025), arXiv:2509.15835. @unpublished{nandi_novel_2025,
title = {Novel Quantum Spin Liquid states in the S = 1/2 three-dimensional compound Y_{3}Cu_{2}Sb_{3}O_{14}},
author = {S. Nandi and R. Das and S. Mahapatra and J. Sichelschmidt and M. Hemmida and H. -A. Krug von Nidda and M. Schuller and N. Büttgen and J. Wilkinson and M. P. Saravanan and I. Dasgupta and A. V. Mahajan},
url = {https://arxiv.org/abs/2509.15835},
doi = {10.48550/arXiv.2509.15835},
year = {2025},
date = {2025-09-19},
urldate = {2025-09-19},
abstract = {The three-dimensional S=1/2 system Y3Cu2Sb3O14 consists of two inequivalent Cu2+ ions, each forming edge shared triangular lattices. Our magnetic susceptibility chi(T)=M/H , specific heat C_p(T), Y nuclear magnetic resonance (NMR), muon spin relaxation (µSR), and electron spin resonance (ESR) measurements on this system confirm the absence of any long-range magnetic ordering and the persistence of spin dynamics down to 0.077 K. From ^89Y NMR we find evidence of a transition at about 120 K which we suggest to arise from a fraction of the spins condensing into a singlet (a valence bond solid VBS or a quantum spin liquid QSL) state. A plateau in the muon relaxation rate is observed between 60 K and 10 K (signifying the VBS/QSL state from a fraction of the spins) followed by an increase and another plateau below about 1 K (presumably signifying the VBS/QSL state from all the spins). Our density functional theory calculations find a dominant antiferromagnetic interaction along the body diagonal with inequivalent Cu(1) and Cu(2) ions alternately occupying the corners of the cube. All other near neighbour interactions between the Cu ions are also found to be antiferromagnetic and are thought to drive the frustration.},
note = {arXiv:2509.15835},
keywords = {B4},
pubstate = {published},
tppubtype = {unpublished}
}
The three-dimensional S=1/2 system Y3Cu2Sb3O14 consists of two inequivalent Cu2+ ions, each forming edge shared triangular lattices. Our magnetic susceptibility chi(T)=M/H , specific heat C_p(T), Y nuclear magnetic resonance (NMR), muon spin relaxation (µSR), and electron spin resonance (ESR) measurements on this system confirm the absence of any long-range magnetic ordering and the persistence of spin dynamics down to 0.077 K. From ^89Y NMR we find evidence of a transition at about 120 K which we suggest to arise from a fraction of the spins condensing into a singlet (a valence bond solid VBS or a quantum spin liquid QSL) state. A plateau in the muon relaxation rate is observed between 60 K and 10 K (signifying the VBS/QSL state from a fraction of the spins) followed by an increase and another plateau below about 1 K (presumably signifying the VBS/QSL state from all the spins). Our density functional theory calculations find a dominant antiferromagnetic interaction along the body diagonal with inequivalent Cu(1) and Cu(2) ions alternately occupying the corners of the cube. All other near neighbour interactions between the Cu ions are also found to be antiferromagnetic and are thought to drive the frustration. | |
Schilberth, F.; Kondákor, M.; Ukolov, D.; Pawbake, A.; Vasin, K.; Ercem, O.; Prodan, L.; Tsurkan, V.; Tsirlin, A. A.; Faugeras, C.; Lemmens, P.; Penc, K.; Kézsmárki, I.; Bordács, S.; Deisenhofer, J. Optical phonons as a testing ground for spin group symmetries Unpublished (2025), arXiv.2508.09793. @unpublished{schilberth_optical_2025,
title = {Optical phonons as a testing ground for spin group symmetries},
author = {F. Schilberth and M. Kondákor and D. Ukolov and A. Pawbake and K. Vasin and O. Ercem and L. Prodan and V. Tsurkan and A. A. Tsirlin and C. Faugeras and P. Lemmens and K. Penc and I. Kézsmárki and S. Bordács and J. Deisenhofer},
url = {https://arxiv.org/abs/2508.09793},
doi = {10.48550/arXiv.2508.09793},
year = {2025},
date = {2025-08-13},
urldate = {2025-08-01},
abstract = {Lattice vibrations are highly sensitive to crystal symmetries and their changes across phase transitions. The latter can modify irreducible (co)representations and corresponding infrared and Raman selection rules of phonons. This concept is established for relativistic magnetic point groups, simultaneously transforming spatial and spin coordinates. However, in altermagnets described by non-relativistic spin groups with disjunct symmetry operations for both vector spaces, the phonon selection rules have remained unexplored. Here, we present a detailed study of the infrared- and Raman-active modes in the collinear antiferromagnet and altermagnet candidate Co2Mo3O8. Comparing to ab initio calculations accurately capturing the eigenfrequencies, we identify all expected phonon modes at room temperature and deduce their selection rules using both symmetry approaches. Importantly, we observe the change of selection rules upon antiferromagnetic ordering, agreeing with the relativistic symmetry approach, while the spin group formalism predicts no changes. Therefore, optical phonons can reveal the appropriate symmetry treatment.},
note = {arXiv.2508.09793},
keywords = {B1, C4},
pubstate = {published},
tppubtype = {unpublished}
}
Lattice vibrations are highly sensitive to crystal symmetries and their changes across phase transitions. The latter can modify irreducible (co)representations and corresponding infrared and Raman selection rules of phonons. This concept is established for relativistic magnetic point groups, simultaneously transforming spatial and spin coordinates. However, in altermagnets described by non-relativistic spin groups with disjunct symmetry operations for both vector spaces, the phonon selection rules have remained unexplored. Here, we present a detailed study of the infrared- and Raman-active modes in the collinear antiferromagnet and altermagnet candidate Co2Mo3O8. Comparing to ab initio calculations accurately capturing the eigenfrequencies, we identify all expected phonon modes at room temperature and deduce their selection rules using both symmetry approaches. Importantly, we observe the change of selection rules upon antiferromagnetic ordering, agreeing with the relativistic symmetry approach, while the spin group formalism predicts no changes. Therefore, optical phonons can reveal the appropriate symmetry treatment. | |
Magar, A.; Somesh, K.; Saravanan, M. P.; Sichelschmidt, J.; Skourski, Y.; Telling, M. T. F.; Ginga, V. A.; Tsirlin, A. A.; Nath, R. Proximate spin-liquid behavior in the double trillium lattice antiferromagnet K2Co2(SO4)3 Unpublished (2025), arXiv.2508.07687. @unpublished{magar_proximate_2025,
title = {Proximate spin-liquid behavior in the double trillium lattice antiferromagnet K_{2}Co_{2}(SO_{4})_{3}},
author = {A. Magar and K. Somesh and M. P. Saravanan and J. Sichelschmidt and Y. Skourski and M. T. F. Telling and V. A. Ginga and A. A. Tsirlin and R. Nath},
url = {https://arxiv.org/abs/2508.07687},
doi = {10.48550/arXiv.2508.07687},
year = {2025},
date = {2025-08-11},
urldate = {2025-08-11},
abstract = {We report proximate quantum spin liquid behavior in K2Co2(SO4)3 with the magnetic Co2+ ions embedded on a highly frustrated three-dimensional double trillium lattice. Single-crystal and high-resolution synchrotron powder x-ray diffraction experiments reveal a structural phase transition at Tt=125K from high-temperature cubic to low-temperature monoclinic phase with the three-fold superstructure. Magnetization and heat capacity consistently show the formation of the Jee=1/2 state of Co2+ below 50 K. In zero field, K2Co2(SO4)3 shows signatures of static magnetic order formed below T*=0.6K, but muon spin relaxation experiments reveal a large fluctuating component that persists down to at least 50mK, reminiscent of quantum spin liquid (QSL). Static order is completely suppressed in the small magnetic field of 1T, and low-temperature heat capacity demonstrates the Tˆ2 behavior above this field, another fingerprint of QSL. Ab initio calculations show a competition of several antiferromagnetic couplings that render K2Co2(SO4)3 a promising pseudospin-1/2 material for studying quantum magnetism in the double trillium lattice geometry.},
note = {arXiv.2508.07687},
keywords = {B3},
pubstate = {published},
tppubtype = {unpublished}
}
We report proximate quantum spin liquid behavior in K2Co2(SO4)3 with the magnetic Co2+ ions embedded on a highly frustrated three-dimensional double trillium lattice. Single-crystal and high-resolution synchrotron powder x-ray diffraction experiments reveal a structural phase transition at Tt=125K from high-temperature cubic to low-temperature monoclinic phase with the three-fold superstructure. Magnetization and heat capacity consistently show the formation of the Jee=1/2 state of Co2+ below 50 K. In zero field, K2Co2(SO4)3 shows signatures of static magnetic order formed below T*=0.6K, but muon spin relaxation experiments reveal a large fluctuating component that persists down to at least 50mK, reminiscent of quantum spin liquid (QSL). Static order is completely suppressed in the small magnetic field of 1T, and low-temperature heat capacity demonstrates the Tˆ2 behavior above this field, another fingerprint of QSL. Ab initio calculations show a competition of several antiferromagnetic couplings that render K2Co2(SO4)3 a promising pseudospin-1/2 material for studying quantum magnetism in the double trillium lattice geometry. | |
Toyoda, S.; Kocsis, V.; Tokunaga, Y.; Kézsmárki, I.; Taguchi, Y.; Arima, T.; Tokura, Y.; Ogawa, N. All-optical control of antiferromagnetic domains via an inverse optical magnetoelectric effect Unpublished (2025), arXiv:2506.07051. @unpublished{toyoda_all-optical_2025,
title = {All-optical control of antiferromagnetic domains via an inverse optical magnetoelectric effect},
author = {S. Toyoda and V. Kocsis and Y. Tokunaga and I. Kézsmárki and Y. Taguchi and T. Arima and Y. Tokura and N. Ogawa},
url = {https://arxiv.org/abs/2506.07051},
doi = {10.48550/arXiv.2506.07051},
year = {2025},
date = {2025-06-08},
urldate = {2025-06-01},
abstract = {Antiferromagnets are a promising platform for next-generation spintronics due to their ultrafast spin dynamics and robustness to external fields. All-optical control of antiferromagnetic order is essential to fully exploit their potential in energy-efficient and high-speed spintronic and memory applications. However, optical writing of antiferromagnetic domains remains a fundamental challenge, as conventional magneto-optical techniques rely on net magnetization, which is absent in antiferromagnets. In certain multiferroic antiferromagnets, the magnetic toroidal moment provides an additional degree of freedom through its inherent magnetoelectric coupling. This coupling at higher frequencies results in the optical magnetoelectric effect (OME), which manifests as a directional asymmetry in light propagation and enables optical probing of antiferromagnetic states. Here, we demonstrate all-optical writing of antiferromagnetic domains using the inverse optical magnetoelectric effect (IOME) in ferrotoroidic LiNiPO4. The writing process is nonvolatile, non-thermal, and deterministic, driven solely by reversing the light propagation direction. This directional control arises from a strong coupling between the photon linear momentum and the magnetic toroidal moment, enabling the repeatable switching between time-reversed domains with arbitrary light polarization. Our findings establish IOME as a distinct mechanism for manipulating antiferromagnetic order, opening a new paradigm in opto-magnetism driven by photon momentum.},
note = {arXiv:2506.07051},
keywords = {C2},
pubstate = {published},
tppubtype = {unpublished}
}
Antiferromagnets are a promising platform for next-generation spintronics due to their ultrafast spin dynamics and robustness to external fields. All-optical control of antiferromagnetic order is essential to fully exploit their potential in energy-efficient and high-speed spintronic and memory applications. However, optical writing of antiferromagnetic domains remains a fundamental challenge, as conventional magneto-optical techniques rely on net magnetization, which is absent in antiferromagnets. In certain multiferroic antiferromagnets, the magnetic toroidal moment provides an additional degree of freedom through its inherent magnetoelectric coupling. This coupling at higher frequencies results in the optical magnetoelectric effect (OME), which manifests as a directional asymmetry in light propagation and enables optical probing of antiferromagnetic states. Here, we demonstrate all-optical writing of antiferromagnetic domains using the inverse optical magnetoelectric effect (IOME) in ferrotoroidic LiNiPO4. The writing process is nonvolatile, non-thermal, and deterministic, driven solely by reversing the light propagation direction. This directional control arises from a strong coupling between the photon linear momentum and the magnetic toroidal moment, enabling the repeatable switching between time-reversed domains with arbitrary light polarization. Our findings establish IOME as a distinct mechanism for manipulating antiferromagnetic order, opening a new paradigm in opto-magnetism driven by photon momentum. | |
Schilberth, F.; DeFreitas, L.; Zhao, K.; LeMardelé, F.; Mohelsky, I.; Orlita, M.; Gegenwart, P.; Chen, H.; Kézsmárki, I.; Bordács, S. Large magnetoreflectance and optical anisotropy due to 4f flat bands in the frustrated kagome magnet HoAgGe Unpublished (2025), arXiv.2504.10274. @unpublished{schilberth_large_2025,
title = {Large magnetoreflectance and optical anisotropy due to 4f flat bands in the frustrated kagome magnet HoAgGe},
author = {F. Schilberth and L. DeFreitas and K. Zhao and F. LeMardelé and I. Mohelsky and M. Orlita and P. Gegenwart and H. Chen and I. Kézsmárki and S. Bordács},
url = {https://arxiv.org/abs/2504.10274},
doi = {10.48550/arXiv.2504.10274},
year = {2025},
date = {2025-04-14},
urldate = {2025-04-01},
abstract = {We report peculiar optical properties of the frustrated itinerant magnet HoAgGe, which exhibits multiple magnetically ordered states obeying the kagome spin-ice rule. The optical conductivity is surprisingly higher for light polarization perpendicular to the kagome plane, both for the free carrier response and the interband transitions. The latter ones have strong contributions from Ho 4f flat bands located near the Fermi level, as revealed by our textbackslashtextitab initio calculations, explaining the unusual anisotropy of the optical properties and the pronounced temperature dependence of the interband transitions for out–of–plane light polarization. The key role of Ho 4f states is further supported by the large variation of the reflectivity upon the metamagnetic transitions, that follows the field dependence of the magnetization, in contrast to that of the dc magnetotransport data. Such heavy-electron bands near the Fermi level offer an efficient way to control transport and optical properties.},
note = {arXiv.2504.10274},
keywords = {A1, B3},
pubstate = {published},
tppubtype = {unpublished}
}
We report peculiar optical properties of the frustrated itinerant magnet HoAgGe, which exhibits multiple magnetically ordered states obeying the kagome spin-ice rule. The optical conductivity is surprisingly higher for light polarization perpendicular to the kagome plane, both for the free carrier response and the interband transitions. The latter ones have strong contributions from Ho 4f flat bands located near the Fermi level, as revealed by our textbackslashtextitab initio calculations, explaining the unusual anisotropy of the optical properties and the pronounced temperature dependence of the interband transitions for out–of–plane light polarization. The key role of Ho 4f states is further supported by the large variation of the reflectivity upon the metamagnetic transitions, that follows the field dependence of the magnetization, in contrast to that of the dc magnetotransport data. Such heavy-electron bands near the Fermi level offer an efficient way to control transport and optical properties. | |
Scheuchenpflug, L.; Esser, S.; Gruhl, R.; Hirschberger, M.; Gegenwart, P. Current-linear emergent induction of pinned skyrmion textures in an oxide bilayer Unpublished (2025), arXiv:2503.10600. @unpublished{scheuchenpflug_current-linear_2025,
title = {Current-linear emergent induction of pinned skyrmion textures in an oxide bilayer},
author = {L. Scheuchenpflug and S. Esser and R. Gruhl and M. Hirschberger and P. Gegenwart},
url = {https://arxiv.org/abs/2503.10600},
doi = {10.48550/arXiv.2503.10600},
year = {2025},
date = {2025-03-13},
urldate = {2025-03-13},
abstract = {Emergent electromagnetic induction (EEMI) induced through current-driven spin dynamics was recently predicted and subsequently observed in helical spin magnets, opening a new direction in spintronics and paving the way towards further miniaturization of electronic circuit elements. In contrast to conventional inductors consisting of coil-like structures whose inductance shows a linear dependence on the cross-section , emergent inductors exhibit an inverse (textasciitildeAˆ-1) proportionality, favorable for the miniaturization of electrical devices. However, the expected current-linear response of the EEMI voltage has not been demonstrated. Magnetic skyrmions hold promise as a simple platform to study the conceptual foundations of EEMI from current-driven spin dynamics. We fabricated devices of thin film bilayers of ferromagnetic SrRuO3 and paramagnetic SrIrO3, which are known to host interfacial Néel skyrmions detected by the appearance of a topological Hall-effect (THE). A large, positive and current-linear inductive response is found to accompany the THE. In our experiment, the current-induced dynamics of pinned magnetic skyrmions creates a voltage both parallel and perpendicular to the applied electric current flow, corresponding to longitudinal and transverse induction, respectively. This is the first report of transverse EEMI, indicating an angle of 80° between skyrmion motion and the applied current. Our observation of current-linear longitudinal and transverse EEMI is a hallmark of pinned dynamics of magnetic skyrmion textures in oxide heterostructures.},
note = {arXiv:2503.10600},
keywords = {B5},
pubstate = {published},
tppubtype = {unpublished}
}
Emergent electromagnetic induction (EEMI) induced through current-driven spin dynamics was recently predicted and subsequently observed in helical spin magnets, opening a new direction in spintronics and paving the way towards further miniaturization of electronic circuit elements. In contrast to conventional inductors consisting of coil-like structures whose inductance shows a linear dependence on the cross-section , emergent inductors exhibit an inverse (textasciitildeAˆ-1) proportionality, favorable for the miniaturization of electrical devices. However, the expected current-linear response of the EEMI voltage has not been demonstrated. Magnetic skyrmions hold promise as a simple platform to study the conceptual foundations of EEMI from current-driven spin dynamics. We fabricated devices of thin film bilayers of ferromagnetic SrRuO3 and paramagnetic SrIrO3, which are known to host interfacial Néel skyrmions detected by the appearance of a topological Hall-effect (THE). A large, positive and current-linear inductive response is found to accompany the THE. In our experiment, the current-induced dynamics of pinned magnetic skyrmions creates a voltage both parallel and perpendicular to the applied electric current flow, corresponding to longitudinal and transverse induction, respectively. This is the first report of transverse EEMI, indicating an angle of 80° between skyrmion motion and the applied current. Our observation of current-linear longitudinal and transverse EEMI is a hallmark of pinned dynamics of magnetic skyrmion textures in oxide heterostructures. | |
Nandi, S.; Jawale, M.; Bachhar, S.; Kumar, Rahul; Schuller, M.; Bag, R.; Wilkinson, J.; Sichelschmidt, J.; Sundaresan, A.; Haravifard, S.; Büttgen, N.; Mahajan, A. V. Observation of the dimer-singlet phase in the one-dimensional S = 1/2 Heisenberg antiferromagnet Cu(Ampy)ClBr (Ampy= C6H8N2 = 2-(Aminomethyl)pyridine) Unpublished (2025), arXiv.2503.10290. @unpublished{nandi_observation_2025,
title = {Observation of the dimer-singlet phase in the one-dimensional S = 1/2 Heisenberg antiferromagnet Cu(Ampy)ClBr (Ampy= C_{6}H_{8}N_{2} = 2-(Aminomethyl)pyridine)},
author = {S. Nandi and M. Jawale and S. Bachhar and Rahul Kumar and M. Schuller and R. Bag and J. Wilkinson and J. Sichelschmidt and A. Sundaresan and S. Haravifard and N. Büttgen and A. V. Mahajan},
url = {https://arxiv.org/abs/2503.10290},
doi = {10.48550/arXiv.2503.10290},
year = {2025},
date = {2025-03-13},
urldate = {2025-03-01},
abstract = {Spin-1/2 Heisenberg antiferromagnetic frustrated spin chain systems display exotic ground states with unconventional excitations and distinct quantum phase transitions as the ratio of next-nearest-neighbor to nearest-neighbor coupling is tuned. We present a comprehensive investigation of the structural, magnetic, and thermodynamics properties of the spin-1/2 compound, Cu(Ampy)ClBr (Ampy= C6H8N2 = 2-(Aminomethyl)pyridine) via x-ray diffraction, magnetization, specific heat, 1H nuclear magnetic resonance (NMR), electron spin resonance (ESR), and muon spin relaxation (muSR) techniques. The crystal structure features an anisotropic triangular chain lattice of magnetic Cu2+ ions. Our bulk and local probe experiments detect neither long-range magnetic ordering nor spin freezing down to 0.06 K despite the presence of moderate antiferromagnetic interaction between Cu2+ spins as reflected by a Curie-Weiss temperature of about -9 K from the bulk susceptibility data. A broad maximum is observed at about 9 K in magnetic susceptibility and specific heat data, indicating the onset of short-range spin correlations. At low temperatures, the zero-field magnetic specific heat and the 1H NMR spin-lattice relaxation rate follow an exponential temperature dependence, indicating the presence of gapped magnetic excitations. Furthermore, persistent spin dynamics down to 0.088 K observed by zero-field muSR evidences lack of any static magnetism. We attribute these experimental results to the stabilization of a dimer-singlet phase in the presence of a next-near neighbor interaction and of a randomness in the exchange coupling driven by Cl/Br mixing. },
note = {arXiv.2503.10290},
keywords = {B4},
pubstate = {published},
tppubtype = {unpublished}
}
Spin-1/2 Heisenberg antiferromagnetic frustrated spin chain systems display exotic ground states with unconventional excitations and distinct quantum phase transitions as the ratio of next-nearest-neighbor to nearest-neighbor coupling is tuned. We present a comprehensive investigation of the structural, magnetic, and thermodynamics properties of the spin-1/2 compound, Cu(Ampy)ClBr (Ampy= C6H8N2 = 2-(Aminomethyl)pyridine) via x-ray diffraction, magnetization, specific heat, 1H nuclear magnetic resonance (NMR), electron spin resonance (ESR), and muon spin relaxation (muSR) techniques. The crystal structure features an anisotropic triangular chain lattice of magnetic Cu2+ ions. Our bulk and local probe experiments detect neither long-range magnetic ordering nor spin freezing down to 0.06 K despite the presence of moderate antiferromagnetic interaction between Cu2+ spins as reflected by a Curie-Weiss temperature of about -9 K from the bulk susceptibility data. A broad maximum is observed at about 9 K in magnetic susceptibility and specific heat data, indicating the onset of short-range spin correlations. At low temperatures, the zero-field magnetic specific heat and the 1H NMR spin-lattice relaxation rate follow an exponential temperature dependence, indicating the presence of gapped magnetic excitations. Furthermore, persistent spin dynamics down to 0.088 K observed by zero-field muSR evidences lack of any static magnetism. We attribute these experimental results to the stabilization of a dimer-singlet phase in the presence of a next-near neighbor interaction and of a randomness in the exchange coupling driven by Cl/Br mixing. | |
Shen, B.; Du, F.; Breitner, F.; Ginga, V. A.; Uykur, E.; Tsirlin, A. A.; Gegenwart, P. Pressure-induced strange metal phase in a metallic kagome ferromagnet Unpublished (2025), arXiv.2503.09524. @unpublished{shen_pressure-induced_2025,
title = {Pressure-induced strange metal phase in a metallic kagome ferromagnet},
author = {B. Shen and F. Du and F. Breitner and V. A. Ginga and E. Uykur and A. A. Tsirlin and P. Gegenwart},
url = {https://arxiv.org/abs/2503.09524},
doi = {10.48550/arXiv.2503.09524},
year = {2025},
date = {2025-03-12},
urldate = {2025-03-12},
abstract = {Strange metallicity with T-linear electrical resistance preceding high-Tc superconductivity remains an enigmatic, yet crucial, signature of correlation physics. Using electrical transport and magnetization measurements up to 50 GPa, we show that such a strange-metal phase is formed in pressurized kagome ferromagnet CrNiAs. In contrast to other kagome materials, a linear suppression of the Curie temperature is found, with the ferromagnetic quantum critical point at pc=12.5GPa. Remarkably, from pc up to the highest measured pressure, characteristic strange-metal behavior is observed, whereas magnetic field reinstates the Fermi liquid. Electronic structure calculations reveal robust weakly dispersive bands persisting unchanged beyond pc, possibly at the origin of the T-linear electrical resistance. This establishes pressurized kagome ferromagnets as an intriguing platform for strange-metal behavior.},
note = {arXiv.2503.09524},
keywords = {B3},
pubstate = {published},
tppubtype = {unpublished}
}
Strange metallicity with T-linear electrical resistance preceding high-Tc superconductivity remains an enigmatic, yet crucial, signature of correlation physics. Using electrical transport and magnetization measurements up to 50 GPa, we show that such a strange-metal phase is formed in pressurized kagome ferromagnet CrNiAs. In contrast to other kagome materials, a linear suppression of the Curie temperature is found, with the ferromagnetic quantum critical point at pc=12.5GPa. Remarkably, from pc up to the highest measured pressure, characteristic strange-metal behavior is observed, whereas magnetic field reinstates the Fermi liquid. Electronic structure calculations reveal robust weakly dispersive bands persisting unchanged beyond pc, possibly at the origin of the T-linear electrical resistance. This establishes pressurized kagome ferromagnets as an intriguing platform for strange-metal behavior. | |
2024
|
Tang, N.; Gen, M.; Rotter, M.; Man, H.; Matsuhira, K.; Matsuo, A.; Kindo, K.; Ikeda, A.; Matsuda, Y.; Gegenwart, P.; Nakatsuji, S.; Kohama, Y. Crystal field magnetostriction of spin ice under ultrahigh magnetic fields Journal Article Phys. Rev. B 110, 214414 (2024). @article{tang_crystal_2024,
title = {Crystal field magnetostriction of spin ice under ultrahigh magnetic fields},
author = {N. Tang and M. Gen and M. Rotter and H. Man and K. Matsuhira and A. Matsuo and K. Kindo and A. Ikeda and Y. Matsuda and P. Gegenwart and S. Nakatsuji and Y. Kohama},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.214414},
doi = {10.1103/PhysRevB.110.214414},
year = {2024},
date = {2024-12-09},
urldate = {2024-12-01},
journal = {Phys. Rev. B},
volume = {110},
number = {21},
pages = {214414},
abstract = {We present a comprehensive study of the magnetoelastic properties of the Ising pyrochlore oxide Ho2Ti2O7, known as spin ice, by means of high-field magnetostriction measurements and numerical calculations. When a magnetic field is applied along the crystallographic ⟨111⟩ axis, the longitudinal magnetostriction exhibits a broad maximum in the low-field regime around 30 T, followed by a dramatic lattice contraction due to crystal-field (CF) level crossing at 𝐵cf∼65 T. The transverse magnetostriction exhibits a contrasting behavior, highlighting the anisotropic nature of the CF striction. By applying a magnetic field at varying sweep rates, we identify distinct timescales of spin dynamics that are relevant to monopole formation and annihilation, as well as CF-phonon dynamics. Our mean-field calculations, based on a point-charge model, successfully reproduce the overall magnetostriction behavior, revealing the competition between the exchange striction and CF striction. A signature of the CF level crossing is also observed through adiabatic magnetocaloric-effect measurements, consistent with our magnetostriction data.},
keywords = {B3, B5},
pubstate = {published},
tppubtype = {article}
}
We present a comprehensive study of the magnetoelastic properties of the Ising pyrochlore oxide Ho2Ti2O7, known as spin ice, by means of high-field magnetostriction measurements and numerical calculations. When a magnetic field is applied along the crystallographic ⟨111⟩ axis, the longitudinal magnetostriction exhibits a broad maximum in the low-field regime around 30 T, followed by a dramatic lattice contraction due to crystal-field (CF) level crossing at 𝐵cf∼65 T. The transverse magnetostriction exhibits a contrasting behavior, highlighting the anisotropic nature of the CF striction. By applying a magnetic field at varying sweep rates, we identify distinct timescales of spin dynamics that are relevant to monopole formation and annihilation, as well as CF-phonon dynamics. Our mean-field calculations, based on a point-charge model, successfully reproduce the overall magnetostriction behavior, revealing the competition between the exchange striction and CF striction. A signature of the CF level crossing is also observed through adiabatic magnetocaloric-effect measurements, consistent with our magnetostriction data. | |
Winkler, M.; Geirhos, K.; Tyborowski, T.; Tóth, B.; Farkas, D. G.; White, J. S.; Ito, T.; Krohns, S.; Lunkenheimer, P.; Bordács, S.; Kézsmárki, I. Anisotropic magnetocapacitance of antiferromagnetic cycloids in BiFeO3 Journal Article Appl. Phys. Lett. 125, 252902 (2024). @article{winkler_anisotropic_2024,
title = {Anisotropic magnetocapacitance of antiferromagnetic cycloids in BiFeO_{3}},
author = {M. Winkler and K. Geirhos and T. Tyborowski and B. Tóth and D. G. Farkas and J. S. White and T. Ito and S. Krohns and P. Lunkenheimer and S. Bordács and I. Kézsmárki},
url = {https://doi.org/10.1063/5.0237659},
doi = {10.1063/5.0237659},
year = {2024},
date = {2024-12-01},
urldate = {2024-12-01},
journal = {Appl. Phys. Lett.},
volume = {125},
number = {25},
pages = {252902},
abstract = {Distinguishing different antiferromagnetic domains by electrical probes is a challenging task, which in itinerant compounds can be achieved, e.g., via the anisotropic magnetoresistance. Here, we demonstrate that in insulators, the anisotropic magnetocapacitance can be exploited for the same purpose. We studied the magnetic field dependence of the dielectric response in BiFeO3, one of the few room-temperature multiferroics. We observed a sizeable dielectric anisotropy upon the rotation of the modulation vector of the antiferromagnetic cycloid in the plane normal to the rhombohedral axis. Importantly, this anisotropy is characteristic of the cycloidal mono-domain state even in zero magnetic field, thus facilitating the determination of the antiferromagnetic domain population. This approach can be utilized to electrically distinguish between antiferromagnetic domains even in complex magnets, such as modulated spin structures, via the magnetodielectric coupling.},
keywords = {A4},
pubstate = {published},
tppubtype = {article}
}
Distinguishing different antiferromagnetic domains by electrical probes is a challenging task, which in itinerant compounds can be achieved, e.g., via the anisotropic magnetoresistance. Here, we demonstrate that in insulators, the anisotropic magnetocapacitance can be exploited for the same purpose. We studied the magnetic field dependence of the dielectric response in BiFeO3, one of the few room-temperature multiferroics. We observed a sizeable dielectric anisotropy upon the rotation of the modulation vector of the antiferromagnetic cycloid in the plane normal to the rhombohedral axis. Importantly, this anisotropy is characteristic of the cycloidal mono-domain state even in zero magnetic field, thus facilitating the determination of the antiferromagnetic domain population. This approach can be utilized to electrically distinguish between antiferromagnetic domains even in complex magnets, such as modulated spin structures, via the magnetodielectric coupling. | |
Leeb, V.; Knolle, J. Numerical study of quantum oscillations of quasiparticle lifetime: Impurity spectroscopy and electric field and strain effects Journal Article Phys. Rev. B 110, 195143 (2024). @article{leeb_numerical_2024,
title = {Numerical study of quantum oscillations of quasiparticle lifetime: Impurity spectroscopy and electric field and strain effects},
author = {V. Leeb and J. Knolle},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.195143},
doi = {10.1103/PhysRevB.110.195143},
year = {2024},
date = {2024-11-21},
urldate = {2024-11-01},
journal = {Phys. Rev. B},
volume = {110},
number = {19},
pages = {195143},
abstract = {Quantum oscillation (QO) measurements constitute one of the most powerful methods for determining the Fermi surface (FS) of metals, exploiting the famous Onsager relation between the FS area and the QO frequency. The recent observation of non-Onsager QOs with a frequency set by the difference of two FS orbits in a bulk three-dimensional metal can be understood as the QO of quasiparticle lifetime (QPL) due to interorbital scattering [N. Huber et al., Nature (London) 621, 276 (2023)]. QPL oscillations (QPLOs) generalize magnetointersubband oscillations known from coupled two-dimensional metals. They may provide a novel tool for extracting otherwise hard-to-measure intraband versus interband scattering times of quasiparticles. Here, we provide a numerical lattice study of QPLOs comparing transport and thermodynamic observables. We explore the effect of different imperfections like general impurities, Hall-effect-induced electric fields, various forms of strain from bending, and magnetic field inhomogeneities. We confirm the basic phenomenology of QPLOs as predicted in analytical calculations and identify additional nonperturbative features. Remarkably, we find that some imperfections can stabilize, or even enhance, non-Onsager QPLOs in contrast to standard QO frequencies. We discuss various avenues for identifying QPLOs in experiments and how to use their dependence on imperfections to extract material properties.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quantum oscillation (QO) measurements constitute one of the most powerful methods for determining the Fermi surface (FS) of metals, exploiting the famous Onsager relation between the FS area and the QO frequency. The recent observation of non-Onsager QOs with a frequency set by the difference of two FS orbits in a bulk three-dimensional metal can be understood as the QO of quasiparticle lifetime (QPL) due to interorbital scattering [N. Huber et al., Nature (London) 621, 276 (2023)]. QPL oscillations (QPLOs) generalize magnetointersubband oscillations known from coupled two-dimensional metals. They may provide a novel tool for extracting otherwise hard-to-measure intraband versus interband scattering times of quasiparticles. Here, we provide a numerical lattice study of QPLOs comparing transport and thermodynamic observables. We explore the effect of different imperfections like general impurities, Hall-effect-induced electric fields, various forms of strain from bending, and magnetic field inhomogeneities. We confirm the basic phenomenology of QPLOs as predicted in analytical calculations and identify additional nonperturbative features. Remarkably, we find that some imperfections can stabilize, or even enhance, non-Onsager QPLOs in contrast to standard QO frequencies. We discuss various avenues for identifying QPLOs in experiments and how to use their dependence on imperfections to extract material properties. | |
Abdeldaim, A. H.; Gretarsson, H.; Day, S. J.; Le, M. D.; Stenning, G. B. G.; Manuel, P.; Perry, R. S.; Tsirlin, A. A.; Nilsen, G. J.; Clark, L. Kitaev Interactions Through an Extended Superexchange Pathway in the jeff = 1/2 Ru3+ Honeycomb Magnet RuP3SiO11 Journal Article Nat. Commun. 15, 9778 (2024). @article{abdeldaim_kitaev_2024,
title = {Kitaev Interactions Through an Extended Superexchange Pathway in the j_{eff} = 1/2 Ru^{3+} Honeycomb Magnet RuP_{3}SiO_{11}},
author = {A. H. Abdeldaim and H. Gretarsson and S. J. Day and M. D. Le and G. B. G. Stenning and P. Manuel and R. S. Perry and A. A. Tsirlin and G. J. Nilsen and L. Clark},
doi = {10.1038/s41467-024-53900-3},
year = {2024},
date = {2024-11-15},
urldate = {2024-11-15},
journal = {Nat. Commun.},
volume = {15},
number = {1},
pages = {9778},
abstract = {Magnetic materials are composed of the simple building blocks of magnetic moments on a crystal lattice that interact via magnetic exchange. Yet from this simplicity emerges a remarkable diversity of magnetic states. Some reveal the deep quantum mechanical origins of magnetism, for example, quantum spin liquid (QSL) states in which magnetic moments remain disordered at low temperatures despite being strongly correlated through quantum entanglement. A promising theoretical model of a QSL is the Kitaev model, composed of unusual bond-dependent exchange interactions, but experimentally, this model is challenging to realise. Here we show that the material requirements for the Kitaev QSL survive an extended pseudo-edge-sharing superexchange pathway of Ru3+ octahedra within the honeycomb layers of the inorganic framework solid, RuP3SiO11. We confirm the requisite
state of Ru3+ in RuP3SiO11 and resolve the hierarchy of exchange interactions that provide experimental access to an unexplored region of the Kitaev model.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
Magnetic materials are composed of the simple building blocks of magnetic moments on a crystal lattice that interact via magnetic exchange. Yet from this simplicity emerges a remarkable diversity of magnetic states. Some reveal the deep quantum mechanical origins of magnetism, for example, quantum spin liquid (QSL) states in which magnetic moments remain disordered at low temperatures despite being strongly correlated through quantum entanglement. A promising theoretical model of a QSL is the Kitaev model, composed of unusual bond-dependent exchange interactions, but experimentally, this model is challenging to realise. Here we show that the material requirements for the Kitaev QSL survive an extended pseudo-edge-sharing superexchange pathway of Ru3+ octahedra within the honeycomb layers of the inorganic framework solid, RuP3SiO11. We confirm the requisite
state of Ru3+ in RuP3SiO11 and resolve the hierarchy of exchange interactions that provide experimental access to an unexplored region of the Kitaev model. |  |
Kamenskyi, D.; Vasin, K.; Prodan, L.; Kutko, K.; Khrustalyov, V.; Pavlov, S. G.; Hübers, H. -W. Terahertz Resonant Emission by Optically Excited Infrared-Active Shear Phonons in KY(MoO4)2 Journal Article Adv. Sci. 12, 2407028 (2024). @article{kamenskyi_terahertz_2024,
title = {Terahertz Resonant Emission by Optically Excited Infrared-Active Shear Phonons in KY(MoO_{4})_{2}},
author = {D. Kamenskyi and K. Vasin and L. Prodan and K. Kutko and V. Khrustalyov and S. G. Pavlov and H. -W. Hübers},
url = {https://advanced.onlinelibrary.wiley.com/doi/abs/10.1002/advs.202407028},
doi = {10.1002/advs.202407028},
year = {2024},
date = {2024-11-13},
urldate = {2024-11-01},
journal = {Adv. Sci.},
volume = {12},
number = {2},
pages = {2407028},
abstract = {Abstract The generation of monochromatic electromagnetic radiation in the terahertz (THz) frequency range has remained a challenging task for many decades. Here, the emission of monochromatic sub-THz radiation by optical phonons in the dielectric material KY(MoO4)2 is demonstrated. The layered crystal structure of KY(MoO4)2 causes infrared-active shear lattice vibrations to have energies below 3.7 meV, corresponding to frequencies lower than 900 GHz where solid-state-based monochromatic radiation sources are rare. Directly excited by a 5 ps long broadband THz pulse, infrared-active optical vibrations in KY(MoO4)2 re-emit narrowband sub-THz radiation as a time-varying dipole for tens of picoseconds, which is exceptionally long for oscillators with frequencies below 1 THz. Such a long coherent emission allows for the detection of more than 50 periods of radiation with frequencies of 568 and 860 GHz. The remarkably long decay time together with the chemical stability of the employed material suggests a variety of possible applications in THz technology.},
keywords = {C4},
pubstate = {published},
tppubtype = {article}
}
Abstract The generation of monochromatic electromagnetic radiation in the terahertz (THz) frequency range has remained a challenging task for many decades. Here, the emission of monochromatic sub-THz radiation by optical phonons in the dielectric material KY(MoO4)2 is demonstrated. The layered crystal structure of KY(MoO4)2 causes infrared-active shear lattice vibrations to have energies below 3.7 meV, corresponding to frequencies lower than 900 GHz where solid-state-based monochromatic radiation sources are rare. Directly excited by a 5 ps long broadband THz pulse, infrared-active optical vibrations in KY(MoO4)2 re-emit narrowband sub-THz radiation as a time-varying dipole for tens of picoseconds, which is exceptionally long for oscillators with frequencies below 1 THz. Such a long coherent emission allows for the detection of more than 50 periods of radiation with frequencies of 568 and 860 GHz. The remarkably long decay time together with the chemical stability of the employed material suggests a variety of possible applications in THz technology. | |
Langmann, J.; Eickerling, G.; Prodan, L.; Tsirlin, A. A.; Winkler, M.; Bordács, S.; Tsurkan, V.; Kézsmárki, I. Atomic-Scale Polar Helix in Inorganic Crystals Journal Article Chem. Mater. 36, 11180–11188 (2024). @article{langmann_atomic-scale_2024,
title = {Atomic-Scale Polar Helix in Inorganic Crystals},
author = {J. Langmann and G. Eickerling and L. Prodan and A. A. Tsirlin and M. Winkler and S. Bordács and V. Tsurkan and I. Kézsmárki},
url = {https://doi.org/10.1021/acs.chemmater.4c02060},
doi = {10.1021/acs.chemmater.4c02060},
year = {2024},
date = {2024-11-04},
urldate = {2024-11-01},
journal = {Chem. Mater.},
volume = {36},
number = {22},
pages = {11180–11188},
abstract = {Chiral structures, noncentrosymmetric objects with a given handedness, emerge on all scales in nature. The most well-known chiral form, the helix, has numerous materializations not only on the microscopic scale (DNA, cholesteric liquid crystals, and spin helices) but also on macroscopic and even cosmological scales. The ongoing quest for new types of chiral structures is fueled by a wide range of fascinating phenomena observed in chiral materials, such as nonreciprocal transport and optical processes, electro-optical effects, and chiral amplification and induction. Here, we report a novel route to chirality in antipolar GaTa4Se8 crystals, where the rotation of the electric polarization vector through the unit cell traces out a helix. The determination of atomic positions using X-ray diffraction combined with ab initio calculations reveals that quasi-molecular Ta4Se4 clusters distort upon a phase transition and evoke significant local electric polarization within structural layers of the unit cell. This polarization is found to rotate in 90° steps between neighboring layers, either clockwise or anticlockwise. A similar analysis performed on two archetypal chiral compounds, α-quartz and tellurium, implies that antipolar crystals with screw-axis symmetry may generally host atomic-scale polarization helices with emergent functionalities.},
keywords = {A4, B1},
pubstate = {published},
tppubtype = {article}
}
Chiral structures, noncentrosymmetric objects with a given handedness, emerge on all scales in nature. The most well-known chiral form, the helix, has numerous materializations not only on the microscopic scale (DNA, cholesteric liquid crystals, and spin helices) but also on macroscopic and even cosmological scales. The ongoing quest for new types of chiral structures is fueled by a wide range of fascinating phenomena observed in chiral materials, such as nonreciprocal transport and optical processes, electro-optical effects, and chiral amplification and induction. Here, we report a novel route to chirality in antipolar GaTa4Se8 crystals, where the rotation of the electric polarization vector through the unit cell traces out a helix. The determination of atomic positions using X-ray diffraction combined with ab initio calculations reveals that quasi-molecular Ta4Se4 clusters distort upon a phase transition and evoke significant local electric polarization within structural layers of the unit cell. This polarization is found to rotate in 90° steps between neighboring layers, either clockwise or anticlockwise. A similar analysis performed on two archetypal chiral compounds, α-quartz and tellurium, implies that antipolar crystals with screw-axis symmetry may generally host atomic-scale polarization helices with emergent functionalities. | |
Jin, H. -K.; Knolle, J. Floquet Prethermal Order by Disorder Journal Article Phys. Rev. Research 6, L042033 (2024). @article{jin_floquet_2024,
title = {Floquet Prethermal Order by Disorder},
author = {H. -K. Jin and J. Knolle},
url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.6.L042033},
doi = {10.1103/PhysRevResearch.6.L042033},
year = {2024},
date = {2024-11-04},
urldate = {2024-11-01},
journal = {Phys. Rev. Research},
volume = {6},
pages = {L042033},
abstract = {Frustrated magnets can have accidental ground state degeneracies which may be lifted by various forms of disorder, for example in the form of thermal or quantum fluctuations. This order by disorder (ObD) paradigm is well established in equilibrium and here is generalized to Floquet many-body systems. Investigating a periodically-driven XXZ-compass model on the square lattice, we show that in a prethermal regime, dynamical fluctuations induced by high-frequency drives select a discrete set of states out of a degenerate ground state manifold of the lowest order Floquet Hamiltonian chosen as initial states. Remarkably, prior to the ObD selection, an unusual fluctuating regime emerges leading to a prethermalization timescale scaling linearly with the drive frequency. We argue that prethermal ObD with its unusual approach to the selected states is a generic phenomenon of driven frustrated systems and confirm it in the paradigmatic $J_1-J_2$ XX model.},
keywords = {C6},
pubstate = {published},
tppubtype = {article}
}
Frustrated magnets can have accidental ground state degeneracies which may be lifted by various forms of disorder, for example in the form of thermal or quantum fluctuations. This order by disorder (ObD) paradigm is well established in equilibrium and here is generalized to Floquet many-body systems. Investigating a periodically-driven XXZ-compass model on the square lattice, we show that in a prethermal regime, dynamical fluctuations induced by high-frequency drives select a discrete set of states out of a degenerate ground state manifold of the lowest order Floquet Hamiltonian chosen as initial states. Remarkably, prior to the ObD selection, an unusual fluctuating regime emerges leading to a prethermalization timescale scaling linearly with the drive frequency. We argue that prethermal ObD with its unusual approach to the selected states is a generic phenomenon of driven frustrated systems and confirm it in the paradigmatic $J_1-J_2$ XX model. | |
Radhakrishnan, P.; Rabinovich, K. S.; Boris, A. V.; Fürsich, K.; Minola, M.; Christiani, G.; Logvenov, G.; Keimer, B.; Benckiser, E. Imprinted atomic displacements drive spin–orbital order in a vanadate perovskite Journal Article Nat. Phys. 21, 126 (2024). @article{radhakrishnan_imprinted_2024,
title = {Imprinted atomic displacements drive spin–orbital order in a vanadate perovskite},
author = {P. Radhakrishnan and K. S. Rabinovich and A. V. Boris and K. Fürsich and M. Minola and G. Christiani and G. Logvenov and B. Keimer and E. Benckiser},
url = {https://doi.org/10.1038/s41567-024-02686-8},
doi = {10.1038/s41567-024-02686-8},
year = {2024},
date = {2024-10-29},
urldate = {2024-10-01},
journal = {Nat. Phys.},
volume = {21},
number = {1},
pages = {126},
abstract = {Perovskites with the generic composition ABO3 exhibit an enormous variety of quantum states, such as orbital order, magnetism and superconductivity. Their flexible and comparatively simple structure allows for straightforward chemical substitution and cube-on-cube combination of different compounds in atomically sharp epitaxial heterostructures. Many of the diverse physical properties of perovskites are determined by small deviations from the ideal cubic perovskite structure, which are challenging to control. Here we show that directional imprinting of atomic displacements in the antiferromagnetic Mott insulator YVO3 can be achieved by depositing epitaxial films on different facets of the same isostructural substrate. These facets were chosen such that other well-known control parameters, including lattice and polarity mismatch with the overlayer, remain nearly unchanged. We observe signatures of staggered orbital and magnetic order and demonstrate distinct spin–orbital ordering patterns on different facets. We attribute these results to the influence of specific octahedral rotation and cation displacement patterns, which are imprinted by the substrate facet, on the covalency of the bonds and the superexchange interactions in YVO3. Our results show that substrate-induced templating of lattice distortion patterns constitutes a pathway for materials design beyond established strain-engineering strategies.},
keywords = {B2},
pubstate = {published},
tppubtype = {article}
}
Perovskites with the generic composition ABO3 exhibit an enormous variety of quantum states, such as orbital order, magnetism and superconductivity. Their flexible and comparatively simple structure allows for straightforward chemical substitution and cube-on-cube combination of different compounds in atomically sharp epitaxial heterostructures. Many of the diverse physical properties of perovskites are determined by small deviations from the ideal cubic perovskite structure, which are challenging to control. Here we show that directional imprinting of atomic displacements in the antiferromagnetic Mott insulator YVO3 can be achieved by depositing epitaxial films on different facets of the same isostructural substrate. These facets were chosen such that other well-known control parameters, including lattice and polarity mismatch with the overlayer, remain nearly unchanged. We observe signatures of staggered orbital and magnetic order and demonstrate distinct spin–orbital ordering patterns on different facets. We attribute these results to the influence of specific octahedral rotation and cation displacement patterns, which are imprinted by the substrate facet, on the covalency of the bonds and the superexchange interactions in YVO3. Our results show that substrate-induced templating of lattice distortion patterns constitutes a pathway for materials design beyond established strain-engineering strategies. | |
Shen, B.; Breitner, F.; Gegenwart, P.; Jesche, A. Strong Enhancement of Magnetic Coercivity Induced by Uniaxial Stress Journal Article Phys. Rev. Lett. 133, 186702 (2024). @article{shen_strong_2024,
title = {Strong Enhancement of Magnetic Coercivity Induced by Uniaxial Stress},
author = {B. Shen and F. Breitner and P. Gegenwart and A. Jesche},
doi = {10.1103/PhysRevLett.133.186702},
year = {2024},
date = {2024-10-28},
urldate = {2024-10-28},
journal = {Phys. Rev. Lett.},
volume = {133},
number = {18},
pages = {186702},
abstract = {The performance of permanent magnets is intricately tied to their magnetic hysteresis loop. In this study, we investigate the heavy-fermion ferromagnet CeAgSb2 through magnetization measurements under uniaxial stress. We observe a 2400% increase in magnetic coercivity with just a modest stress of approximately 1 kbar. This effect persists even after pressure release, attributable to stress-induced defects that efficiently pin domain walls. Other magnetic properties such as ordering temperature and saturation moment exhibit only weak pressure dependencies and display full reversibility. Our findings offer a promising route for increasing coercive field strength and enhancing the energy product in ferromagnetic materials and are potentially applicable to a broad spectrum of commercial or emerging magnetic applications.},
keywords = {B1, B3},
pubstate = {published},
tppubtype = {article}
}
The performance of permanent magnets is intricately tied to their magnetic hysteresis loop. In this study, we investigate the heavy-fermion ferromagnet CeAgSb2 through magnetization measurements under uniaxial stress. We observe a 2400% increase in magnetic coercivity with just a modest stress of approximately 1 kbar. This effect persists even after pressure release, attributable to stress-induced defects that efficiently pin domain walls. Other magnetic properties such as ordering temperature and saturation moment exhibit only weak pressure dependencies and display full reversibility. Our findings offer a promising route for increasing coercive field strength and enhancing the energy product in ferromagnetic materials and are potentially applicable to a broad spectrum of commercial or emerging magnetic applications. | |
Davenport, H.; Knolle, J.; Schindler, F. Interaction-Induced Crystalline Topology of Excitons Journal Article Phys. Rev. Lett. 133, 176601 (2024). @article{davenport_interaction-induced_2024,
title = {Interaction-Induced Crystalline Topology of Excitons},
author = {H. Davenport and J. Knolle and F. Schindler},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.133.176601},
doi = {10.1103/PhysRevLett.133.176601},
year = {2024},
date = {2024-10-21},
urldate = {2024-10-01},
journal = {Phys. Rev. Lett.},
volume = {133},
number = {17},
pages = {176601},
abstract = {We apply the topological theory of symmetry indicators to interaction-induced exciton band structures in centrosymmetric semiconductors. Crucially, we distinguish between the topological invariants inherited from the underlying electron and hole bands and those that are intrinsic to the exciton wave function itself. Focusing on the latter, we show that there exists a class of exciton bands for which the maximally localized exciton Wannier states are shifted with respect to the electronic Wannier states by a quantized amount; we call these excitons shift excitons. Our analysis explains how the exciton spectrum can be topologically nontrivial and sustain exciton edge states in open boundary conditions even when the underlying noninteracting bands have a trivial atomic limit. We demonstrate the presence of shift excitons as the lowest energy neutral excitations of the Su-Schrieffer-Heeger model in its trivial phase when supplemented by local two-body interactions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We apply the topological theory of symmetry indicators to interaction-induced exciton band structures in centrosymmetric semiconductors. Crucially, we distinguish between the topological invariants inherited from the underlying electron and hole bands and those that are intrinsic to the exciton wave function itself. Focusing on the latter, we show that there exists a class of exciton bands for which the maximally localized exciton Wannier states are shifted with respect to the electronic Wannier states by a quantized amount; we call these excitons shift excitons. Our analysis explains how the exciton spectrum can be topologically nontrivial and sustain exciton edge states in open boundary conditions even when the underlying noninteracting bands have a trivial atomic limit. We demonstrate the presence of shift excitons as the lowest energy neutral excitations of the Su-Schrieffer-Heeger model in its trivial phase when supplemented by local two-body interactions. | |
Mukharjee, P. K.; Shen, B.; Erdmann, S.; Jesche, A.; Kaiser, J.; Baral, P. R.; Zaharko, O.; Gegenwart, P.; Tsirlin, A. A. Intermediate field-induced phase of the honeycomb magnet BaCo2(AsO4)2 Journal Article Phys. Rev. B 110, L140407 (2024). @article{mukharjee_intermediate_2024,
title = {Intermediate field-induced phase of the honeycomb magnet BaCo_{2}(AsO_{4})_{2}},
author = {P. K. Mukharjee and B. Shen and S. Erdmann and A. Jesche and J. Kaiser and P. R. Baral and O. Zaharko and P. Gegenwart and A. A. Tsirlin},
doi = {10.1103/PhysRevB.110.L140407},
year = {2024},
date = {2024-10-21},
urldate = {2024-10-21},
journal = {Phys. Rev. B},
volume = {110},
number = {14},
pages = {L140407},
abstract = {We use magnetometry, calorimetry, and high-resolution capacitive dilatometry, as well as single-crystal neutron diffraction to explore the temperature-field phase diagram of the anisotropic honeycomb magnet BaCo2(AsO4)2. Our data reveal four distinct ordered states observed for in-plane magnetic fields. Of particular interest is the narrow region between 0.51 and 0.54 T that separates the up-up-down order from the fully polarized state and coincides with the field range where signatures of the spin-liquid behavior have been reported. We show that magnetic Bragg peaks persist in this intermediate phase, thus ruling out its spin-liquid nature. However, the simultaneous nonmonotonic evolution of nuclear Bragg peaks suggests the involvement of the lattice, witnessed also in other regions of the phase diagram where large changes in the sample length are observed upon entering the magnetically ordered states. Our data highlight the importance of lattice effects in BaCo2(AsO4)2.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
We use magnetometry, calorimetry, and high-resolution capacitive dilatometry, as well as single-crystal neutron diffraction to explore the temperature-field phase diagram of the anisotropic honeycomb magnet BaCo2(AsO4)2. Our data reveal four distinct ordered states observed for in-plane magnetic fields. Of particular interest is the narrow region between 0.51 and 0.54 T that separates the up-up-down order from the fully polarized state and coincides with the field range where signatures of the spin-liquid behavior have been reported. We show that magnetic Bragg peaks persist in this intermediate phase, thus ruling out its spin-liquid nature. However, the simultaneous nonmonotonic evolution of nuclear Bragg peaks suggests the involvement of the lattice, witnessed also in other regions of the phase diagram where large changes in the sample length are observed upon entering the magnetically ordered states. Our data highlight the importance of lattice effects in BaCo2(AsO4)2. | |
Birnkammer, S.; Knolle, J.; Knap, M. Signatures of domain-wall confinement in Raman spectroscopy of Ising spin chains Journal Article Phys. Rev. B 110, 134408 (2024). @article{birnkammer_signatures_2024,
title = {Signatures of domain-wall confinement in Raman spectroscopy of Ising spin chains},
author = {S. Birnkammer and J. Knolle and M. Knap},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.134408},
doi = {10.1103/PhysRevB.110.134408},
year = {2024},
date = {2024-10-03},
urldate = {2024-10-01},
journal = {Phys. Rev. B},
volume = {110},
number = {13},
pages = {134408},
abstract = {Mesonic bound states of domain walls (DWs) can be stabilized in quasi-one-dimensional magnetic compounds. Here, we theoretically study the Raman light scattering response of a twisted Kitaev chain with tilted magnetic fields as a minimal model for confinement in CoNb2O6. By both numerical matrix product states and few-DW variational states, we show that confinement-induced bound states directly manifest themselves as sharp peaks in the Raman response. Remarkably, by tuning the polarization of the incident light field, we demonstrate that the Raman response offers insights into the intrinsic symmetry of the bound-state wave function.},
keywords = {C6},
pubstate = {published},
tppubtype = {article}
}
Mesonic bound states of domain walls (DWs) can be stabilized in quasi-one-dimensional magnetic compounds. Here, we theoretically study the Raman light scattering response of a twisted Kitaev chain with tilted magnetic fields as a minimal model for confinement in CoNb2O6. By both numerical matrix product states and few-DW variational states, we show that confinement-induced bound states directly manifest themselves as sharp peaks in the Raman response. Remarkably, by tuning the polarization of the incident light field, we demonstrate that the Raman response offers insights into the intrinsic symmetry of the bound-state wave function. | |
Säubert, S.; Franz, C.; Jochum, J. K.; Benka, G.; Bauer, A.; Shapiro, S. M.; Böni, P.; Pfleiderer, C. Evolution of spin dynamics during freezing in the spin-glass FexCr1-x Journal Article Phys. Rev. B 110, 094422 (2024). @article{saubert_evolution_2024,
title = {Evolution of spin dynamics during freezing in the spin-glass Fe_{x}Cr_{1-x}},
author = {S. Säubert and C. Franz and J. K. Jochum and G. Benka and A. Bauer and S. M. Shapiro and P. Böni and C. Pfleiderer},
doi = {10.1103/PhysRevB.110.094422},
year = {2024},
date = {2024-09-13},
urldate = {2024-09-13},
journal = {Phys. Rev. B},
volume = {110},
number = {9},
pages = {094422},
abstract = {In the iron–chromium system, Fe𝑥Cr1−𝑥, a wide dome of spin-glass behavior emerges when the ferromagnetism of iron is suppressed and the antiferromagnetism of chromium emerges as a function of increasing iron content 𝑥. As both, the high-temperature state and the characteristic cluster size vary as a function of 𝑥, different regimes of spin-glass behavior may be compared in a single, isostructural material system. Here, we report a study of the spin dynamics across the freezing process into the spin-glass state for different iron concentrations (𝑥=0.145, 0.175, 0.21) using modulation of intensity with zero effort (MIEZE) spectroscopy. In the parameter range studied, the relaxation process observed experimentally may be described well in terms of a stretched exponential. In the reentrant cluster-glass regime, 𝑥=0.145, this behavior persists up to high temperatures. In comparison, in the superparamagnetic regime, 𝑥=0.175 and 𝑥=0.21, a single relaxation time at elevated temperatures is observed. For all samples studied, the spin relaxation exhibits a momentum dependence consistent with a power law, providing evidence of a dispersive character of the spin relaxation.},
keywords = {C1, C3},
pubstate = {published},
tppubtype = {article}
}
In the iron–chromium system, Fe𝑥Cr1−𝑥, a wide dome of spin-glass behavior emerges when the ferromagnetism of iron is suppressed and the antiferromagnetism of chromium emerges as a function of increasing iron content 𝑥. As both, the high-temperature state and the characteristic cluster size vary as a function of 𝑥, different regimes of spin-glass behavior may be compared in a single, isostructural material system. Here, we report a study of the spin dynamics across the freezing process into the spin-glass state for different iron concentrations (𝑥=0.145, 0.175, 0.21) using modulation of intensity with zero effort (MIEZE) spectroscopy. In the parameter range studied, the relaxation process observed experimentally may be described well in terms of a stretched exponential. In the reentrant cluster-glass regime, 𝑥=0.145, this behavior persists up to high temperatures. In comparison, in the superparamagnetic regime, 𝑥=0.175 and 𝑥=0.21, a single relaxation time at elevated temperatures is observed. For all samples studied, the spin relaxation exhibits a momentum dependence consistent with a power law, providing evidence of a dispersive character of the spin relaxation. | |
Hofmeier, D.; Willsher, J.; Seifert, U. F. P.; Knolle, J. Spin-Peierls instability of deconfined quantum critical points Journal Article Phys. Rev. B 110, 125130 (2024). @article{hofmeier_spin-peierls_2024,
title = {Spin-Peierls instability of deconfined quantum critical points},
author = {D. Hofmeier and J. Willsher and U. F. P. Seifert and J. Knolle},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.125130},
doi = {10.1103/PhysRevB.110.125130},
year = {2024},
date = {2024-09-13},
urldate = {2024-09-01},
journal = {Phys. Rev. B},
volume = {110},
number = {12},
pages = {125130},
abstract = {Deconfined quantum critical points (DQCPs) are putative phase transitions beyond the Landau paradigm with emergent fractionalized degrees of freedom. The original example of a DQCP is the spin-1/2 quantum antiferromagnet on the square lattice which features a second-order transition between valence bond solid (VBS) and Néel order. The VBS order breaks a lattice symmetry, and the corresponding VBS order parameter may couple to lattice distortion modes (phonons) at appropriate momenta. We investigate a field-theoretic description of the DQCP in the presence of such a spin-lattice coupling. We show that treating phonons as classical lattice distortions leads to a relevant monopole-phonon interaction inducing an instability towards a distorted lattice by an analogous mechanism to the spin-Peierls instability in one dimension. Consequently, there is a breakdown of the DQCP which generally becomes a strong first-order transition. Taking into account the full quantum nature of the phonons, we argue that the continuous DQCP persists above a critical phonon frequency. Lastly, we comment on the connection to general gapless, deconfined gauge theories.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
Deconfined quantum critical points (DQCPs) are putative phase transitions beyond the Landau paradigm with emergent fractionalized degrees of freedom. The original example of a DQCP is the spin-1/2 quantum antiferromagnet on the square lattice which features a second-order transition between valence bond solid (VBS) and Néel order. The VBS order breaks a lattice symmetry, and the corresponding VBS order parameter may couple to lattice distortion modes (phonons) at appropriate momenta. We investigate a field-theoretic description of the DQCP in the presence of such a spin-lattice coupling. We show that treating phonons as classical lattice distortions leads to a relevant monopole-phonon interaction inducing an instability towards a distorted lattice by an analogous mechanism to the spin-Peierls instability in one dimension. Consequently, there is a breakdown of the DQCP which generally becomes a strong first-order transition. Taking into account the full quantum nature of the phonons, we argue that the continuous DQCP persists above a critical phonon frequency. Lastly, we comment on the connection to general gapless, deconfined gauge theories. | |
Prodan, L.; Chmeruk, A.; Chioncel, L.; Tsurkan, V.; Kézsmárki, I. Anisotropic charge transport in the easy-plane kagome ferromagnet Fe3Sn Journal Article Phys. Rev. B 110, 094407 (2024). @article{prodan_anisotropic_2024,
title = {Anisotropic charge transport in the easy-plane kagome ferromagnet Fe_{3}Sn},
author = {L. Prodan and A. Chmeruk and L. Chioncel and V. Tsurkan and I. Kézsmárki},
doi = {10.1103/PhysRevB.110.094407},
year = {2024},
date = {2024-09-05},
urldate = {2024-09-05},
journal = {Phys. Rev. B},
volume = {110},
number = {9},
pages = {094407},
abstract = {We report on the anisotropic electronic properties of the metallic kagome ferromagnet , as revealed by magnetotransport studies on single-crystalline samples and material-specific ab initio calculations. The longitudinal resistivity shows a remarkable anisotropy, where surprisingly the resistivity perpendicular to the kagome planes is about three times lower than the in-plane resistivity (𝜌𝑥𝑥). The ordinary Hall constants are negative for the magnetic field applied parallel to the 𝐇||𝐜 and positive for 𝐇||𝐚, indicating the coexistence of electron- and hole-like carriers at the Fermi surface. The anomalous Hall resistivity (𝜌𝐴𝑖𝑗) shows large values over a wide temperature range and exhibits a significant anisotropy ratio (𝜌𝑥𝑦/𝜌𝑧𝑦), with 𝜌𝑥𝑦 =8 µΩcm and 𝜌𝑧𝑦 =3.2 µΩcm at room temperature. Our study reveals that the anisotropy ratio scales almost linearly with the magnetocrystalline anisotropy constant (𝐾𝑢) over a broad temperature range (2 K ≤ T ≤ 300 K), indicating that spin-orbit coupling is the underlying mechanism driving both the anisotropic transport properties and the magnetocrystalline anisotropy energy. Material-specific ab initio calculations further demonstrate that the magnetic reconstruction of bands near the Fermi level, induced by the spin-orbit coupling, is predominantly responsible for the anisotropic behavior of the Berry curvature and, consequently, the large anomalous Hall effect observed in Fe3Sn. These results provide valuable insight into the complex interplay between charge transport and magnetism in kagome magnets, emphasizing the strong manifestation of spin-orbit coupling on kagome lattices.},
keywords = {A1, A5},
pubstate = {published},
tppubtype = {article}
}
We report on the anisotropic electronic properties of the metallic kagome ferromagnet , as revealed by magnetotransport studies on single-crystalline samples and material-specific ab initio calculations. The longitudinal resistivity shows a remarkable anisotropy, where surprisingly the resistivity perpendicular to the kagome planes is about three times lower than the in-plane resistivity (𝜌𝑥𝑥). The ordinary Hall constants are negative for the magnetic field applied parallel to the 𝐇||𝐜 and positive for 𝐇||𝐚, indicating the coexistence of electron- and hole-like carriers at the Fermi surface. The anomalous Hall resistivity (𝜌𝐴𝑖𝑗) shows large values over a wide temperature range and exhibits a significant anisotropy ratio (𝜌𝑥𝑦/𝜌𝑧𝑦), with 𝜌𝑥𝑦 =8 µΩcm and 𝜌𝑧𝑦 =3.2 µΩcm at room temperature. Our study reveals that the anisotropy ratio scales almost linearly with the magnetocrystalline anisotropy constant (𝐾𝑢) over a broad temperature range (2 K ≤ T ≤ 300 K), indicating that spin-orbit coupling is the underlying mechanism driving both the anisotropic transport properties and the magnetocrystalline anisotropy energy. Material-specific ab initio calculations further demonstrate that the magnetic reconstruction of bands near the Fermi level, induced by the spin-orbit coupling, is predominantly responsible for the anisotropic behavior of the Berry curvature and, consequently, the large anomalous Hall effect observed in Fe3Sn. These results provide valuable insight into the complex interplay between charge transport and magnetism in kagome magnets, emphasizing the strong manifestation of spin-orbit coupling on kagome lattices. | |
Jin, H. -K.; Kadow, W.; Knap, M.; Knolle, J. Kinetic ferromagnetism and topological magnons of the hole-doped Kitaev spin liquid Journal Article npj Quantum Mater. 9, 65 (2024). @article{jin_kinetic_2024,
title = {Kinetic ferromagnetism and topological magnons of the hole-doped Kitaev spin liquid},
author = {H. -K. Jin and W. Kadow and M. Knap and J. Knolle},
doi = {10.1038/s41535-024-00678-8},
year = {2024},
date = {2024-09-04},
urldate = {2024-09-01},
journal = {npj Quantum Mater.},
volume = {9},
number = {1},
pages = {65},
abstract = {We study the effect of hole doping on the Kitaev spin liquid (KSL) and find that for ferromagnetic (FM) Kitaev exchange K the system is very susceptible to the formation of a FM spin polarization. Through density matrix renormalization group simulations on finite systems, we uncover that the introduction of a single hole, corresponding to ≈1% hole doping for the system size we consider, with a hopping strength of just t textasciitilde 0.28K is enough to disrupt fractionalization and polarize the spins in the [001] direction due to an order-by-disorder mechanism. Taking into account a material relevant FM anisotropic exchange Γ drives the polarization towards the [111] direction via a transition into a topological FM state with chiral magnon excitations. We develop a parton mean-field theory incorporating fermionic holons and bosonic magnons, which accounts for the doping induced FM phases and topological magnon excitations. We discuss experimental implications for Kitaev candidate materials.},
keywords = {C6},
pubstate = {published},
tppubtype = {article}
}
We study the effect of hole doping on the Kitaev spin liquid (KSL) and find that for ferromagnetic (FM) Kitaev exchange K the system is very susceptible to the formation of a FM spin polarization. Through density matrix renormalization group simulations on finite systems, we uncover that the introduction of a single hole, corresponding to ≈1% hole doping for the system size we consider, with a hopping strength of just t textasciitilde 0.28K is enough to disrupt fractionalization and polarize the spins in the [001] direction due to an order-by-disorder mechanism. Taking into account a material relevant FM anisotropic exchange Γ drives the polarization towards the [111] direction via a transition into a topological FM state with chiral magnon excitations. We develop a parton mean-field theory incorporating fermionic holons and bosonic magnons, which accounts for the doping induced FM phases and topological magnon excitations. We discuss experimental implications for Kitaev candidate materials. | |
Chen, L.; Sun, Y.; Mankovsky, S.; Meier, T. N. G.; Kronseder, M.; Sun, C.; Orekhov, A.; Ebert, H.; Weiss, D.; Back, C. H. Signatures of magnetism control by flow of angular momentum Journal Article Nature 633, 548–553 (2024). @article{chen_signatures_2024,
title = {Signatures of magnetism control by flow of angular momentum},
author = {L. Chen and Y. Sun and S. Mankovsky and T. N. G. Meier and M. Kronseder and C. Sun and A. Orekhov and H. Ebert and D. Weiss and C. H. Back},
doi = {10.1038/s41586-024-07914-y},
issn = {1476-4687},
year = {2024},
date = {2024-09-04},
urldate = {2024-09-01},
journal = {Nature},
volume = {633},
number = {8030},
pages = {548–553},
abstract = {Exploring new strategies to manipulate the order parameter of magnetic materials by electrical means is of great importance not only for advancing our understanding of fundamental magnetism but also for unlocking potential applications. A well-established concept uses gate voltages to control magnetic properties by modulating the carrier population in a capacitor structure1–5. Here we show that, in Pt/Al/Fe/GaAs(001) multilayers, the application of an in-plane charge current in Pt leads to a shift in the ferromagnetic resonance field depending on the microwave frequency when the Fe film is sufficiently thin. The experimental observation is interpreted as a current-induced modification of the magnetocrystalline anisotropy ΔHA of Fe. We show that (1) ΔHA decreases with increasing Fe film thickness and is connected to the damping-like torque; and (2) ΔHA depends not only on the polarity of charge current but also on the magnetization direction, that is, ΔHA has an opposite sign when the magnetization direction is reversed. The symmetry of the modification is consistent with a current-induced spin6–8 and/or orbit9–13 accumulation, which, respectively, act on the spin and/or orbit component of the magnetization. In this study, as Pt is regarded as a typical spin current source6,14, the spin current can play a dominant part. The control of magnetism by a spin current results from the modified exchange splitting of the majority and minority spin bands, providing functionality that was previously unknown and could be useful in advanced spintronic devices.},
keywords = {A2},
pubstate = {published},
tppubtype = {article}
}
Exploring new strategies to manipulate the order parameter of magnetic materials by electrical means is of great importance not only for advancing our understanding of fundamental magnetism but also for unlocking potential applications. A well-established concept uses gate voltages to control magnetic properties by modulating the carrier population in a capacitor structure1–5. Here we show that, in Pt/Al/Fe/GaAs(001) multilayers, the application of an in-plane charge current in Pt leads to a shift in the ferromagnetic resonance field depending on the microwave frequency when the Fe film is sufficiently thin. The experimental observation is interpreted as a current-induced modification of the magnetocrystalline anisotropy ΔHA of Fe. We show that (1) ΔHA decreases with increasing Fe film thickness and is connected to the damping-like torque; and (2) ΔHA depends not only on the polarity of charge current but also on the magnetization direction, that is, ΔHA has an opposite sign when the magnetization direction is reversed. The symmetry of the modification is consistent with a current-induced spin6–8 and/or orbit9–13 accumulation, which, respectively, act on the spin and/or orbit component of the magnetization. In this study, as Pt is regarded as a typical spin current source6,14, the spin current can play a dominant part. The control of magnetism by a spin current results from the modified exchange splitting of the majority and minority spin bands, providing functionality that was previously unknown and could be useful in advanced spintronic devices. | |
Seifert, U. F. P.; Willsher, J.; Drescher, M.; Pollmann, F.; Knolle, J. Spin-Peierls instability of the U(1) Dirac spin liquid Journal Article Nat. Commun. 15, 7110 (2024). @article{seifert_spin-peierls_2024,
title = {Spin-Peierls instability of the U(1) Dirac spin liquid},
author = {U. F. P. Seifert and J. Willsher and M. Drescher and F. Pollmann and J. Knolle},
url = {https://doi.org/10.1038/s41467-024-51367-w},
doi = {10.1038/s41467-024-51367-w},
year = {2024},
date = {2024-08-19},
urldate = {2024-08-01},
journal = {Nat. Commun.},
volume = {15},
number = {1},
pages = {7110},
abstract = {Quantum fluctuations can inhibit long-range ordering in frustrated magnets and potentially lead to quantum spin liquid (QSL) phases. A prime example are gapless QSLs with emergent U(1) gauge fields, which have been understood to be described in terms of quantum electrodynamics in 2+1 dimension (QED3). Despite several promising candidate materials, however, a complicating factor for their realisation is the presence of other degrees of freedom. In particular lattice distortions can act to relieve magnetic frustration, precipitating conventionally ordered states. In this work, we use field-theoretic arguments as well as extensive numerical simulations to show that the U(1) Dirac QSL on the triangular and kagome lattices exhibits a weak-coupling instability due to the coupling of monopoles of the emergent gauge field to lattice distortions, leading to valence-bond solid ordering. This generalises the spin-Peierls instability of one-dimensional quantum critical spin chains to two-dimensional algebraic QSLs. We study static distortions as well as quantum-mechanical phonons. Even in regimes where the QSL is stable, the singular spin-lattice coupling leads to marked temperature-dependent corrections to the phonon spectrum, which provide salient experimental signatures of spin fractionalisation. We discuss the coupling of QSLs to the lattice as a general tool for their discovery and characterisation.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
Quantum fluctuations can inhibit long-range ordering in frustrated magnets and potentially lead to quantum spin liquid (QSL) phases. A prime example are gapless QSLs with emergent U(1) gauge fields, which have been understood to be described in terms of quantum electrodynamics in 2+1 dimension (QED3). Despite several promising candidate materials, however, a complicating factor for their realisation is the presence of other degrees of freedom. In particular lattice distortions can act to relieve magnetic frustration, precipitating conventionally ordered states. In this work, we use field-theoretic arguments as well as extensive numerical simulations to show that the U(1) Dirac QSL on the triangular and kagome lattices exhibits a weak-coupling instability due to the coupling of monopoles of the emergent gauge field to lattice distortions, leading to valence-bond solid ordering. This generalises the spin-Peierls instability of one-dimensional quantum critical spin chains to two-dimensional algebraic QSLs. We study static distortions as well as quantum-mechanical phonons. Even in regimes where the QSL is stable, the singular spin-lattice coupling leads to marked temperature-dependent corrections to the phonon spectrum, which provide salient experimental signatures of spin fractionalisation. We discuss the coupling of QSLs to the lattice as a general tool for their discovery and characterisation. | |
Hemmida, M.; Masell, J.; Karube, K.; Ehlers, D.; von Nidda, H. -A. Krug; Tsurkan, V.; Tokura, Y.; Taguchi, Y.; Kézsmárki, I. Role of magnetic anisotropy in the antiskyrmion-host schreibersite magnets Journal Article Phys. Rev. B 110, 054416 (2024). @article{hemmida_role_2024,
title = {Role of magnetic anisotropy in the antiskyrmion-host schreibersite magnets},
author = {M. Hemmida and J. Masell and K. Karube and D. Ehlers and H. -A. Krug von Nidda and V. Tsurkan and Y. Tokura and Y. Taguchi and I. Kézsmárki},
doi = {10.1103/PhysRevB.110.054416},
year = {2024},
date = {2024-08-08},
urldate = {2024-08-08},
journal = {Phys. Rev. B},
volume = {110},
number = {5},
pages = {054416},
keywords = {B4},
pubstate = {published},
tppubtype = {article}
}
| |
Kirchner, N.; Choi, W.; Pollmann, F. Characterizing the entanglement of anyonic systems using the anyonic partial transpose Journal Article Phys. Rev. B 110, 085143 (2024). @article{kirchner_characterizing_2024,
title = {Characterizing the entanglement of anyonic systems using the anyonic partial transpose},
author = {N. Kirchner and W. Choi and F. Pollmann},
doi = {10.1103/PhysRevB.110.085143},
year = {2024},
date = {2024-08-01},
urldate = {2024-08-01},
journal = {Phys. Rev. B},
volume = {110},
number = {8},
pages = {085143},
abstract = {Entanglement of mixed quantum states can be quantified using the partial transpose and its corresponding entanglement measure, the logarithmic negativity. Recently, the notion of partial transpose has been extended to systems of anyons, which are exotic quasiparticles whose exchange statistics go beyond the bosonic and fermionic cases. Studying the fundamental properties of this anyonic partial transpose, we first reveal that when applied to the special case of fermionic systems, it can be reduced to the fermionic partial transpose or its twisted variant depending on whether or not a boundary Majorana fermion is present. Focusing on ground state properties, we find that the anyonic partial transpose captures both the correct entanglement scaling for gapless systems, as predicted by conformal field theory, and the phase transition between a topologically trivial and a nontrivial phase. For non-Abelian anyons and the bipartition geometry, we find a rich multiplet structure in the eigenvalues of the partial transpose, the so-called negativity spectrum, and reveal the possibility of defining both a charge- and an imbalance-resolved negativity.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Entanglement of mixed quantum states can be quantified using the partial transpose and its corresponding entanglement measure, the logarithmic negativity. Recently, the notion of partial transpose has been extended to systems of anyons, which are exotic quasiparticles whose exchange statistics go beyond the bosonic and fermionic cases. Studying the fundamental properties of this anyonic partial transpose, we first reveal that when applied to the special case of fermionic systems, it can be reduced to the fermionic partial transpose or its twisted variant depending on whether or not a boundary Majorana fermion is present. Focusing on ground state properties, we find that the anyonic partial transpose captures both the correct entanglement scaling for gapless systems, as predicted by conformal field theory, and the phase transition between a topologically trivial and a nontrivial phase. For non-Abelian anyons and the bipartition geometry, we find a rich multiplet structure in the eigenvalues of the partial transpose, the so-called negativity spectrum, and reveal the possibility of defining both a charge- and an imbalance-resolved negativity. | |
Vasin, K. V.; Strinić, A.; Schilberth, F.; Reschke, S.; Prodan, L.; Tsurkan, V.; Nurmukhametov, A. R.; Eremin, M. V.; Kézsmárki, I.; Deisenhofer, J. Optical magnetoelectric effect in the polar honeycomb antiferromagnet Fe2Mo3O8 Journal Article Phys. Rev. B 110, 054401 (2024). @article{vasin_optical_2024,
title = {Optical magnetoelectric effect in the polar honeycomb antiferromagnet Fe_{2}Mo_{3}O_{8}},
author = {K. V. Vasin and A. Strinić and F. Schilberth and S. Reschke and L. Prodan and V. Tsurkan and A. R. Nurmukhametov and M. V. Eremin and I. Kézsmárki and J. Deisenhofer},
doi = {10.1103/PhysRevB.110.054401},
year = {2024},
date = {2024-08-01},
urldate = {2024-08-01},
journal = {Phys. Rev. B},
volume = {110},
number = {5},
pages = {054401},
abstract = {The lack of both time-reversal and spatial inversion symmetry in polar magnets is a prerequisite for the occurrence of optical magnetoelectric effects such as nonreciprocal directional dichroism, i.e., a difference in refractive index and absorption for two counter-propagating electromagnetic waves, which has the potential for the realization of optical diodes. In particular, antiferromagnetic materials with magnetic excitations in the THz range such as Fe2Mo3O8 are promising candidates for next-generation spintronic applications. In a combined experimental and theoretical effort we investigated the THz excitations of the polar honeycomb antiferromagnet Fe2Mo3O8 in external magnetic fields and their nonreciprocal directional dichroism, together with the temperature dependence of the electronic transitions in the mid- and near-infrared frequency range. Using an advanced single-ion approach for the Fe ions, we are able to describe optical excitations from the THz to the near-infrared frequency range quantitatively and model the observed nonreciprocal directional dichroism in the THz regime successfully.},
keywords = {A1, C4},
pubstate = {published},
tppubtype = {article}
}
The lack of both time-reversal and spatial inversion symmetry in polar magnets is a prerequisite for the occurrence of optical magnetoelectric effects such as nonreciprocal directional dichroism, i.e., a difference in refractive index and absorption for two counter-propagating electromagnetic waves, which has the potential for the realization of optical diodes. In particular, antiferromagnetic materials with magnetic excitations in the THz range such as Fe2Mo3O8 are promising candidates for next-generation spintronic applications. In a combined experimental and theoretical effort we investigated the THz excitations of the polar honeycomb antiferromagnet Fe2Mo3O8 in external magnetic fields and their nonreciprocal directional dichroism, together with the temperature dependence of the electronic transitions in the mid- and near-infrared frequency range. Using an advanced single-ion approach for the Fe ions, we are able to describe optical excitations from the THz to the near-infrared frequency range quantitatively and model the observed nonreciprocal directional dichroism in the THz regime successfully. | |
Zerba, C.; Kuhlenkamp, C.; Imamoğlu, A.; Knap, M. Realizing topological superconductivity in tunable bose-fermi mixtures with transition metal dichalcogenide heterostructures Journal Article Phys. Rev. Lett. 133, 056902 (2024). @article{zerba_realizing_2024,
title = {Realizing topological superconductivity in tunable bose-fermi mixtures with transition metal dichalcogenide heterostructures},
author = {C. Zerba and C. Kuhlenkamp and A. Imamoğlu and M. Knap},
doi = {10.1103/PhysRevLett.133.056902},
year = {2024},
date = {2024-07-30},
urldate = {2024-07-01},
journal = {Phys. Rev. Lett.},
volume = {133},
number = {5},
pages = {056902},
abstract = {Heterostructures of two-dimensional transition metal dichalcogenides are emerging as a promising platform for investigating exotic correlated states of matter. Here, we propose to engineer Bose-Fermi mixtures in these systems by coupling interlayer excitons to doped charges in a trilayer structure. Their interactions are determined by the interlayer trion, whose spin-selective nature allows excitons to mediate an attractive interaction between charge carriers of only one spin species. Remarkably, we find that this causes the system to become unstable to topological 𝑝+𝑖𝑝 superconductivity at low temperatures. We then demonstrate a general mechanism to develop and control this unconventional state by tuning the trion binding energy using a solid-state Feshbach resonance.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Heterostructures of two-dimensional transition metal dichalcogenides are emerging as a promising platform for investigating exotic correlated states of matter. Here, we propose to engineer Bose-Fermi mixtures in these systems by coupling interlayer excitons to doped charges in a trilayer structure. Their interactions are determined by the interlayer trion, whose spin-selective nature allows excitons to mediate an attractive interaction between charge carriers of only one spin species. Remarkably, we find that this causes the system to become unstable to topological 𝑝+𝑖𝑝 superconductivity at low temperatures. We then demonstrate a general mechanism to develop and control this unconventional state by tuning the trion binding energy using a solid-state Feshbach resonance. | |
Magnaterra, M.; Attig, J.; Peterlini, L.; Hermanns, M.; Upton, M. H.; Kim, Jungho; Prodan, L.; Tsurkan, V.; Kézsmárki, I.; Loosdrecht, P. H. M.; Grüninger, M. Quasimolecular Jtet = 3/2 Moments in the Cluster Mott Insulator GaTa4Se8 Journal Article Phys. Rev. Lett. 133, 046501 (2024). @article{magnaterra_quasimolecular_2024,
title = {Quasimolecular J_{tet} = 3/2 Moments in the Cluster Mott Insulator GaTa_{4}Se_{8}},
author = {M. Magnaterra and J. Attig and L. Peterlini and M. Hermanns and M. H. Upton and Jungho Kim and L. Prodan and V. Tsurkan and I. Kézsmárki and P. H. M. Loosdrecht and M. Grüninger},
doi = {10.1103/PhysRevLett.133.046501},
year = {2024},
date = {2024-07-22},
urldate = {2024-07-22},
journal = {Phys. Rev. Lett.},
volume = {133},
number = {4},
pages = {046501},
keywords = {A1},
pubstate = {published},
tppubtype = {article}
}
| |
Büttgen, N.; von Nidda, H. -A. Krug Magnetic resonance in quantum spin chains with competing exchange interactions Journal Article J. Phys. A: Math. Theor. 57, 313001 (2024). @article{buttgen_magnetic_2024,
title = {Magnetic resonance in quantum spin chains with competing exchange interactions},
author = {N. Büttgen and H. -A. Krug von Nidda},
doi = {10.1088/1751-8121/ad5e4c},
year = {2024},
date = {2024-07-18},
urldate = {2024-07-01},
journal = {J. Phys. A: Math. Theor.},
volume = {57},
number = {31},
pages = {313001},
abstract = {Based on a previous review on magnetic resonance in quantum spin chains (Krug von Nidda et al 2010 Eur. Phys. J. Spec. Top. 180 161–89) we report on further development in this field with special focus on transition–metal oxides and halogenides consisting of quasi one–dimensional spin systems, where both intra–and inter–chain exchange interaction may give rise to frustration effects and higher–order anisotropic exchange contributions like the Dzyaloshinskii–Moriya interaction become decisive for the formation of the magnetic ground state. Selected examples show how NMR and ESR contribute valuable information on the magnetic phases and exchange interactions involved: LiCuVO4 with competing nearest neighbour and next–nearest neighbour intra–chain exchange, LiCu2O2 with complex zig–zag chains, and Cs2CuCl4 where the chains form a triangular lattice with the inter–chain interaction weaker but of the same order of magnitude than the intra–chain interaction. The so called paper–chain compound Ba3Cu3In4O12, where each successive pair of CuO4 plaquettes is rotated by 90° with respect to its predecessor along the c–direction like in a paper–chain, provides an interesting topology of frustrated intra–chain exchange interactions. Finally, a few dimer systems are considered.},
keywords = {B4},
pubstate = {published},
tppubtype = {article}
}
Based on a previous review on magnetic resonance in quantum spin chains (Krug von Nidda et al 2010 Eur. Phys. J. Spec. Top. 180 161–89) we report on further development in this field with special focus on transition–metal oxides and halogenides consisting of quasi one–dimensional spin systems, where both intra–and inter–chain exchange interaction may give rise to frustration effects and higher–order anisotropic exchange contributions like the Dzyaloshinskii–Moriya interaction become decisive for the formation of the magnetic ground state. Selected examples show how NMR and ESR contribute valuable information on the magnetic phases and exchange interactions involved: LiCuVO4 with competing nearest neighbour and next–nearest neighbour intra–chain exchange, LiCu2O2 with complex zig–zag chains, and Cs2CuCl4 where the chains form a triangular lattice with the inter–chain interaction weaker but of the same order of magnitude than the intra–chain interaction. The so called paper–chain compound Ba3Cu3In4O12, where each successive pair of CuO4 plaquettes is rotated by 90° with respect to its predecessor along the c–direction like in a paper–chain, provides an interesting topology of frustrated intra–chain exchange interactions. Finally, a few dimer systems are considered. | |
Kumar, H.; Köpf, M.; Telang, P.; Bura, N.; Jesche, A.; Gegenwart, P.; Kuntscher, C. A. Optical conductivity of the metallic pyrochlore iridate Pr2Ir2O7: Influence of spin-orbit coupling and electronic correlations on the electronic structure Journal Article Phys. Rev. B 110, 035140 (2024). @article{kumar_optical_2024,
title = {Optical conductivity of the metallic pyrochlore iridate Pr_{2}Ir_{2}O_{7}: Influence of spin-orbit coupling and electronic correlations on the electronic structure},
author = {H. Kumar and M. Köpf and P. Telang and N. Bura and A. Jesche and P. Gegenwart and C. A. Kuntscher},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.035140},
doi = {10.1103/PhysRevB.110.035140},
year = {2024},
date = {2024-07-15},
urldate = {2024-07-01},
journal = {Phys. Rev. B},
volume = {110},
number = {3},
pages = {035140},
abstract = {The synergy of strong spin-orbit coupling and electron-electron interactions gives rise to unconventional topological states, such as topological Mott insulator, Weyl semimetal, and quantum spin liquid. In this study, we have grown single crystals of the pyrochlore iridate Pr2Ir2O7 and explored its magnetic, lattice dynamical, and electronic properties. While Raman spectroscopy data reveal six phonon modes confirming the cubic Fd‾3m crystal symmetry, dc magnetic susceptibility data show no anomalies and hence indicate the absence of magnetic phase transitions down to 2 K. Both temperature-dependent electric transport and optical conductivity data reveal the metallic character of Pr2Ir2O7. The optical conductivity spectrum contains a midinfrared absorption band, which becomes more pronounced with decreasing temperature due to spectral weight transfer from high to low energies. The presence of the midinfrared band hints at the importance of correlation physics. The optical response furthermore suggests that Pr2Ir2O7 is close to the Weyl semimetal phase.},
keywords = {A1, B5},
pubstate = {published},
tppubtype = {article}
}
The synergy of strong spin-orbit coupling and electron-electron interactions gives rise to unconventional topological states, such as topological Mott insulator, Weyl semimetal, and quantum spin liquid. In this study, we have grown single crystals of the pyrochlore iridate Pr2Ir2O7 and explored its magnetic, lattice dynamical, and electronic properties. While Raman spectroscopy data reveal six phonon modes confirming the cubic Fd‾3m crystal symmetry, dc magnetic susceptibility data show no anomalies and hence indicate the absence of magnetic phase transitions down to 2 K. Both temperature-dependent electric transport and optical conductivity data reveal the metallic character of Pr2Ir2O7. The optical conductivity spectrum contains a midinfrared absorption band, which becomes more pronounced with decreasing temperature due to spectral weight transfer from high to low energies. The presence of the midinfrared band hints at the importance of correlation physics. The optical response furthermore suggests that Pr2Ir2O7 is close to the Weyl semimetal phase. | |
Kalin, J.; Sievers, S.; Schumacher, H. W.; Füser, H.; Bieler, M.; Bauer, A.; Pfleiderer, C. Influence of the magnetovolume effect on the transient reflectivity of MnSi Journal Article Phys. Rev. B 110, 014415 (2024). @article{kalin_influence_2024,
title = {Influence of the magnetovolume effect on the transient reflectivity of MnSi},
author = {J. Kalin and S. Sievers and H. W. Schumacher and H. Füser and M. Bieler and A. Bauer and C. Pfleiderer},
doi = {10.1103/PhysRevB.110.014415},
year = {2024},
date = {2024-07-11},
urldate = {2024-07-11},
journal = {Phys. Rev. B},
volume = {110},
number = {1},
pages = {014415},
abstract = {The magnetovolume effect is a well established yet frequently overlooked phenomenon in magnetic materials that may affect a wide range of physical properties. Our study explores the influence of the magnetovolume effect on the transient reflectivity of MnSi, a well-known chiral magnet with strong magnetoelastic coupling. We observe a unipolar reflectivity transient in the paramagnetic phase, contrasting with a bipolar response in phases with magnetic long-range order. Comparing our findings with thermal expansion from literature, we establish that the bipolar response originates in the magnetovolume effect which dominates the thermal expansion and influences the optical reflectivity. Our results highlight not only that the magnetovolume effect must be considered when discussing transient reflectivity measurements of magnetic materials but also that such measurements permit to study the characteristic time scales of the magnetovolume effect itself, contributing to a deeper understanding of this often-neglected phenomenon.},
keywords = {C1, C3},
pubstate = {published},
tppubtype = {article}
}
The magnetovolume effect is a well established yet frequently overlooked phenomenon in magnetic materials that may affect a wide range of physical properties. Our study explores the influence of the magnetovolume effect on the transient reflectivity of MnSi, a well-known chiral magnet with strong magnetoelastic coupling. We observe a unipolar reflectivity transient in the paramagnetic phase, contrasting with a bipolar response in phases with magnetic long-range order. Comparing our findings with thermal expansion from literature, we establish that the bipolar response originates in the magnetovolume effect which dominates the thermal expansion and influences the optical reflectivity. Our results highlight not only that the magnetovolume effect must be considered when discussing transient reflectivity measurements of magnetic materials but also that such measurements permit to study the characteristic time scales of the magnetovolume effect itself, contributing to a deeper understanding of this often-neglected phenomenon. | |
Chen, A.; Heyl, M. Empowering deep neural quantum states through efficient optimization Journal Article Nat. Phys. 20, 1476 (2024). @article{chen_empowering_2024,
title = {Empowering deep neural quantum states through efficient optimization},
author = {A. Chen and M. Heyl},
doi = {10.1038/s41567-024-02566-1},
year = {2024},
date = {2024-07-01},
urldate = {2024-07-01},
journal = {Nat. Phys.},
volume = {20},
number = {9},
pages = {1476},
abstract = {Computing the ground state of interacting quantum matter is a long-standing challenge, especially for complex two-dimensional systems. Recent developments have highlighted the potential of neural quantum states to solve the quantum many-body problem by encoding the many-body wavefunction into artificial neural networks. However, this method has faced the critical limitation that existing optimization algorithms are not suitable for training modern large-scale deep network architectures. Here, we introduce a minimum-step stochastic-reconfiguration optimization algorithm, which allows us to train deep neural quantum states with up to 106 parameters. We demonstrate our method for paradigmatic frustrated spin-1/2 models on square and triangular lattices, for which our trained deep networks approach machine precision and yield improved variational energies compared to existing results. Equipped with our optimization algorithm, we find numerical evidence for gapless quantum-spin-liquid phases in the considered models, an open question to date. We present a method that captures the emergent complexity in quantum many-body problems through the expressive power of large-scale artificial neural networks.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
Computing the ground state of interacting quantum matter is a long-standing challenge, especially for complex two-dimensional systems. Recent developments have highlighted the potential of neural quantum states to solve the quantum many-body problem by encoding the many-body wavefunction into artificial neural networks. However, this method has faced the critical limitation that existing optimization algorithms are not suitable for training modern large-scale deep network architectures. Here, we introduce a minimum-step stochastic-reconfiguration optimization algorithm, which allows us to train deep neural quantum states with up to 106 parameters. We demonstrate our method for paradigmatic frustrated spin-1/2 models on square and triangular lattices, for which our trained deep networks approach machine precision and yield improved variational energies compared to existing results. Equipped with our optimization algorithm, we find numerical evidence for gapless quantum-spin-liquid phases in the considered models, an open question to date. We present a method that captures the emergent complexity in quantum many-body problems through the expressive power of large-scale artificial neural networks. | |
Pichler, F.; Kadow, W.; Kuhlenkamp, C.; Knap, M. Probing magnetism in moiré heterostructures with quantum twisting microscopes Journal Article Phys. Rev. B 110, 045116 (2024). @article{pichler_probing_2024,
title = {Probing magnetism in moiré heterostructures with quantum twisting microscopes},
author = {F. Pichler and W. Kadow and C. Kuhlenkamp and M. Knap},
doi = {10.1103/PhysRevB.110.045116},
year = {2024},
date = {2024-07-01},
urldate = {2024-01-01},
journal = {Phys. Rev. B},
volume = {110},
number = {4},
pages = {045116},
abstract = {Spin-ordered states close to metal-insulator transitions are poorly understood theoretically and challenging to probe in experiments. Here, we propose that the quantum twisting microscope, which provides direct access to the energy-momentum resolved spectrum of single-particle and collective excitations, can be used as a novel tool to distinguish between different types of magnetic order. To this end, we calculate the single-particle spectral function and the dynamical spin-structure factor for both a ferromagnetic and antiferromagnetic generalized Wigner crystal formed in fractionally filled moiré superlattices of transition metal dichalcogenide heterostructures. We demonstrate that magnetic order can be clearly identified in these response functions. Furthermore, we explore signatures of quantum phase transitions in the quantum twisting microscope response. We focus on the specific case of triangular moiré lattices at half filling that have been proposed to host a topological phase transition between a chiral spin liquid and a 120° ordered state. Our work demonstrates the potential for quantum twisting microscopes to characterize quantum magnetism in moiré heterostructures.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Spin-ordered states close to metal-insulator transitions are poorly understood theoretically and challenging to probe in experiments. Here, we propose that the quantum twisting microscope, which provides direct access to the energy-momentum resolved spectrum of single-particle and collective excitations, can be used as a novel tool to distinguish between different types of magnetic order. To this end, we calculate the single-particle spectral function and the dynamical spin-structure factor for both a ferromagnetic and antiferromagnetic generalized Wigner crystal formed in fractionally filled moiré superlattices of transition metal dichalcogenide heterostructures. We demonstrate that magnetic order can be clearly identified in these response functions. Furthermore, we explore signatures of quantum phase transitions in the quantum twisting microscope response. We focus on the specific case of triangular moiré lattices at half filling that have been proposed to host a topological phase transition between a chiral spin liquid and a 120° ordered state. Our work demonstrates the potential for quantum twisting microscopes to characterize quantum magnetism in moiré heterostructures. | |
Das, P.; Leeb, V.; Knolle, J.; Knap, M. Realizing altermagnetism in fermi-hubbard models with ultracold atoms Journal Article Phys. Rev. Lett. 132, 263402 (2024). @article{das_realizing_2024,
title = {Realizing altermagnetism in fermi-hubbard models with ultracold atoms},
author = {P. Das and V. Leeb and J. Knolle and M. Knap},
doi = {10.1103/PhysRevLett.132.263402},
year = {2024},
date = {2024-06-26},
urldate = {2024-06-01},
journal = {Phys. Rev. Lett.},
volume = {132},
number = {26},
pages = {263402},
abstract = {Altermagnetism represents a type of collinear magnetism, that is in some aspects distinct from ferromagnetism and from conventional antiferromagnetism. In contrast to the latter, sublattices of opposite spin are related by spatial rotations and not only by translations and inversions. As a result, altermagnets have spin-split bands leading to unique experimental signatures. Here, we show theoretically how a 𝑑-wave altermagnetic phase can be realized with ultracold fermionic atoms in optical lattices. We propose an altermagnetic Hubbard model with anisotropic next-nearest neighbor hopping and obtain the Hartree-Fock phase diagram. The altermagnetic phase separates in a metallic and an insulating phase and is robust over a large parameter regime. We show that one of the defining characteristics of altermagnetism, the anisotropic spin transport, can be probed with trap-expansion experiments.},
keywords = {C6},
pubstate = {published},
tppubtype = {article}
}
Altermagnetism represents a type of collinear magnetism, that is in some aspects distinct from ferromagnetism and from conventional antiferromagnetism. In contrast to the latter, sublattices of opposite spin are related by spatial rotations and not only by translations and inversions. As a result, altermagnets have spin-split bands leading to unique experimental signatures. Here, we show theoretically how a 𝑑-wave altermagnetic phase can be realized with ultracold fermionic atoms in optical lattices. We propose an altermagnetic Hubbard model with anisotropic next-nearest neighbor hopping and obtain the Hartree-Fock phase diagram. The altermagnetic phase separates in a metallic and an insulating phase and is robust over a large parameter regime. We show that one of the defining characteristics of altermagnetism, the anisotropic spin transport, can be probed with trap-expansion experiments. | |
Leeb, V.; Mook, A.; Šmejkal, L.; Knolle, J. Spontaneous Formation of Altermagnetism from Orbital Ordering Journal Article Phys. Rev. Lett. 132, 236701 (2024). @article{leeb_spontaneous_2024,
title = {Spontaneous Formation of Altermagnetism from Orbital Ordering},
author = {V. Leeb and A. Mook and L. Šmejkal and J. Knolle},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.132.236701},
doi = {10.1103/PhysRevLett.132.236701},
year = {2024},
date = {2024-06-03},
urldate = {2024-06-01},
journal = {Phys. Rev. Lett.},
volume = {132},
number = {23},
pages = {236701},
abstract = {Altermagnetism has emerged as a third type of collinear magnetism. In contrast to standard ferromagnets and antiferromagnets, altermagnets exhibit extra even-parity wave spin order parameters resulting in a spin splitting of electronic bands in momentum space. In real space, sublattices of opposite spin polarization are anisotropic and related by rotational symmetry. In the hitherto identified altermagnetic candidate materials, the anisotropies arise from the local crystallographic symmetry. Here, we show that altermagnetism can also form as an interaction-induced electronic instability in a lattice without the crystallographic sublattice anisotropy. We provide a microscopic example of a two-orbital model showing that the coexistence of staggered antiferromagnetic and orbital order can realize robust altermagnetism. We quantify the spin-splitter conductivity as a key experimental observable and discuss material candidates for the interaction-induced realization of altermagnetism.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Altermagnetism has emerged as a third type of collinear magnetism. In contrast to standard ferromagnets and antiferromagnets, altermagnets exhibit extra even-parity wave spin order parameters resulting in a spin splitting of electronic bands in momentum space. In real space, sublattices of opposite spin polarization are anisotropic and related by rotational symmetry. In the hitherto identified altermagnetic candidate materials, the anisotropies arise from the local crystallographic symmetry. Here, we show that altermagnetism can also form as an interaction-induced electronic instability in a lattice without the crystallographic sublattice anisotropy. We provide a microscopic example of a two-orbital model showing that the coexistence of staggered antiferromagnetic and orbital order can realize robust altermagnetism. We quantify the spin-splitter conductivity as a key experimental observable and discuss material candidates for the interaction-induced realization of altermagnetism. | |
Hirschberger, M.; Szigeti, B. G.; Hemmida, M.; Hirschmann, M. M.; Esser, S.; Ohsumi, H.; Tanaka, Y.; Spitz, L.; Gao, S.; Kolincio, K. K.; Sagayama, H.; Nakao, H.; Yamasaki, Y.; Forró, L.; von Nidda, H. -A. Krug; Kézsmárki, I.; Arima, T.; Tokura, Y. Lattice-commensurate skyrmion texture in a centrosymmetric breathing kagome magnet Journal Article npj Quantum Mater. 9, 45 (2024). @article{hirschberger_lattice-commensurate_2024,
title = {Lattice-commensurate skyrmion texture in a centrosymmetric breathing kagome magnet},
author = {M. Hirschberger and B. G. Szigeti and M. Hemmida and M. M. Hirschmann and S. Esser and H. Ohsumi and Y. Tanaka and L. Spitz and S. Gao and K. K. Kolincio and H. Sagayama and H. Nakao and Y. Yamasaki and L. Forró and H. -A. Krug von Nidda and I. Kézsmárki and T. Arima and Y. Tokura},
doi = {10.1038/s41535-024-00654-2},
year = {2024},
date = {2024-05-23},
urldate = {2024-05-01},
journal = {npj Quantum Mater.},
volume = {9},
pages = {45},
abstract = {Skyrmion lattices (SkL) in centrosymmetric materials typically have a magnetic period on the nanometer-scale, so that the coupling between magnetic superstructures and the underlying crystal lattice cannot be neglected. We reveal the commensurate locking of a SkL to the atomic lattice in Gd3Ru4Al12 via high-resolution resonant elastic x-ray scattering (REXS). Weak easy-plane magnetic anisotropy, demonstrated here by a combination of ferromagnetic resonance and REXS, penalizes placing a skyrmion core on a site of the atomic lattice. Under these conditions, a commensurate SkL, locked to the crystal lattice, is stable at finite temperatures – but gives way to a competing incommensurate ground state upon cooling. We discuss the role of Umklapp-terms in the Hamiltonian for the formation of this lattice-locked state, its magnetic space group, and the role of slight discommensurations, or (line) defects in the magnetic texture. We also contrast our findings with the case of SkLs in noncentrosymmetric material platforms.},
keywords = {B4, B5},
pubstate = {published},
tppubtype = {article}
}
Skyrmion lattices (SkL) in centrosymmetric materials typically have a magnetic period on the nanometer-scale, so that the coupling between magnetic superstructures and the underlying crystal lattice cannot be neglected. We reveal the commensurate locking of a SkL to the atomic lattice in Gd3Ru4Al12 via high-resolution resonant elastic x-ray scattering (REXS). Weak easy-plane magnetic anisotropy, demonstrated here by a combination of ferromagnetic resonance and REXS, penalizes placing a skyrmion core on a site of the atomic lattice. Under these conditions, a commensurate SkL, locked to the crystal lattice, is stable at finite temperatures – but gives way to a competing incommensurate ground state upon cooling. We discuss the role of Umklapp-terms in the Hamiltonian for the formation of this lattice-locked state, its magnetic space group, and the role of slight discommensurations, or (line) defects in the magnetic texture. We also contrast our findings with the case of SkLs in noncentrosymmetric material platforms. | |
Matsumoto, Y.; Schnierer, S.; Bruin, J. A. N.; Nuss, J.; Reiss, P.; Jackeli, G.; Kitagawa, K.; Takagi, H. A quantum critical Bose gas of magnons in the quasi-two-dimensional antiferromagnet YbCl3 under magnetic fields Journal Article Nat. Phys. 20, 1131–1138 (2024). @article{matsumoto_quantum_2024,
title = {A quantum critical Bose gas of magnons in the quasi-two-dimensional antiferromagnet YbCl_{3} under magnetic fields},
author = {Y. Matsumoto and S. Schnierer and J. A. N. Bruin and J. Nuss and P. Reiss and G. Jackeli and K. Kitagawa and H. Takagi},
url = {https://doi.org/10.1038/s41567-024-02498-w},
doi = {10.1038/s41567-024-02498-w},
year = {2024},
date = {2024-05-09},
urldate = {2024-05-09},
journal = {Nat. Phys.},
volume = {20},
number = {7},
pages = {1131–1138},
abstract = {Bose–Einstein condensation (BEC) is a quantum phenomenon in which a macroscopic number of bosons occupy the lowest energy state and acquire coherence at low temperatures. In three-dimensional antiferromagnets, a magnetic-field-induced transition has been successfully described as a magnon BEC. For a strictly two-dimensional (2D) system, it is known that BEC cannot take place due to the presence of a finite density of states at zero energy. However, in a realistic quasi-2D magnet consisting of stacked magnetic layers, a small but finite interlayer coupling stabilizes marginal BEC but such that 2D physics is still expected to dominate. This 2D-limit BEC behaviour has been reported in a few materials but only at very high magnetic fields that are difficult to access. The honeycomb S = 1/2 Heisenberg antiferromagnet YbCl3 exhibits a transition to a fully polarized state at a relatively low in-plane magnetic field. Here, we demonstrate the formation of a quantum critical 2D Bose gas at the transition field, which, with lowering the field, experiences a BEC marginally stabilized by an extremely small interlayer coupling. Our observations establish YbCl3, previously a Kitaev quantum spin liquid material, as a realization of a quantum critical BEC in the 2D limit.},
keywords = {A3},
pubstate = {published},
tppubtype = {article}
}
Bose–Einstein condensation (BEC) is a quantum phenomenon in which a macroscopic number of bosons occupy the lowest energy state and acquire coherence at low temperatures. In three-dimensional antiferromagnets, a magnetic-field-induced transition has been successfully described as a magnon BEC. For a strictly two-dimensional (2D) system, it is known that BEC cannot take place due to the presence of a finite density of states at zero energy. However, in a realistic quasi-2D magnet consisting of stacked magnetic layers, a small but finite interlayer coupling stabilizes marginal BEC but such that 2D physics is still expected to dominate. This 2D-limit BEC behaviour has been reported in a few materials but only at very high magnetic fields that are difficult to access. The honeycomb S = 1/2 Heisenberg antiferromagnet YbCl3 exhibits a transition to a fully polarized state at a relatively low in-plane magnetic field. Here, we demonstrate the formation of a quantum critical 2D Bose gas at the transition field, which, with lowering the field, experiences a BEC marginally stabilized by an extremely small interlayer coupling. Our observations establish YbCl3, previously a Kitaev quantum spin liquid material, as a realization of a quantum critical BEC in the 2D limit. | |
Kunze, J.; Köpf, M.; Cao, W.; Qi, Y.; Kuntscher, C. A. Optical signatures of type-II Weyl fermions in the noncentrosymmetric semimetals RAlSi (R = La, Ce, Pr, Nd, Sm) Journal Article Phys. Rev. B 109, 195130 (2024). @article{kunze_optical_2024,
title = {Optical signatures of type-II Weyl fermions in the noncentrosymmetric semimetals RAlSi (R = La, Ce, Pr, Nd, Sm)},
author = {J. Kunze and M. Köpf and W. Cao and Y. Qi and C. A. Kuntscher},
url = {https://link.aps.org/doi/10.1103/PhysRevB.109.195130},
doi = {10.1103/PhysRevB.109.195130},
year = {2024},
date = {2024-05-09},
urldate = {2024-05-09},
journal = {Phys. Rev. B},
volume = {109},
number = {19},
pages = {195130},
abstract = {Weyl semimetals with magnetic ordering provide a promising platform for the investigation of rare topological effects such as the anomalous Hall effect, resulting from the interplay of nontrivial bands with various spin configurations. The materials RAlSi, where R represents a rare-earth element, are prominent representatives of Weyl semimetals, where the Weyl states are induced by space inversion symmetry breaking, and in addition, for several rare-earth elements R, enhanced by time-reversal symmetry breaking through the formation of a magnetic order at low temperature. We report optical signatures of Weyl fermions in the magnetic compounds CeAlSi, PrAlSi, NdAlSi, and SmAlSi as well as the nonmagnetic family member LaAlSi by broad-frequency infrared spectroscopy at room temperature, i.e., in the paramagnetic phase. A similar profile of the optical conductivity spectrum and a metallic character are observed for all compounds, with LaAlSi showing the strongest free charge-carrier contribution. Furthermore, the linear-in-frequency behavior of the optical conductivity of all investigated compounds indicates the presence of Weyl nodes in close proximity to the Fermi energy, resulting from inversion symmetry breaking in noncentrosymmetric structures. According to the characteristics of these linear slopes, the RAlSi compounds are expected to host mainly type-II Weyl states with overtilted Weyl cones. The results are compared to the optical response of the closely related RAlGe materials, which are considered as potential hybridization-driven Weyl-Kondo systems.},
keywords = {A1},
pubstate = {published},
tppubtype = {article}
}
Weyl semimetals with magnetic ordering provide a promising platform for the investigation of rare topological effects such as the anomalous Hall effect, resulting from the interplay of nontrivial bands with various spin configurations. The materials RAlSi, where R represents a rare-earth element, are prominent representatives of Weyl semimetals, where the Weyl states are induced by space inversion symmetry breaking, and in addition, for several rare-earth elements R, enhanced by time-reversal symmetry breaking through the formation of a magnetic order at low temperature. We report optical signatures of Weyl fermions in the magnetic compounds CeAlSi, PrAlSi, NdAlSi, and SmAlSi as well as the nonmagnetic family member LaAlSi by broad-frequency infrared spectroscopy at room temperature, i.e., in the paramagnetic phase. A similar profile of the optical conductivity spectrum and a metallic character are observed for all compounds, with LaAlSi showing the strongest free charge-carrier contribution. Furthermore, the linear-in-frequency behavior of the optical conductivity of all investigated compounds indicates the presence of Weyl nodes in close proximity to the Fermi energy, resulting from inversion symmetry breaking in noncentrosymmetric structures. According to the characteristics of these linear slopes, the RAlSi compounds are expected to host mainly type-II Weyl states with overtilted Weyl cones. The results are compared to the optical response of the closely related RAlGe materials, which are considered as potential hybridization-driven Weyl-Kondo systems. | |
Reinhoffer, C.; Esser, S.; Esser, S.; Mashkovich, E.; Germanskiy, S.; Gegenwart, P.; Anders, F.; Loosdrecht, P. H. M.; Wang, Z. Strong Terahertz Third-Harmonic Generation by Kinetic Heavy Quasiparticles in CaRuO3 Journal Article Phys. Rev. Lett. 132, 196501 (2024). @article{reinhoffer_strong_2024,
title = {Strong Terahertz Third-Harmonic Generation by Kinetic Heavy Quasiparticles in CaRuO_{3}},
author = {C. Reinhoffer and S. Esser and S. Esser and E. Mashkovich and S. Germanskiy and P. Gegenwart and F. Anders and P. H. M. Loosdrecht and Z. Wang},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.132.196501},
doi = {10.1103/PhysRevLett.132.196501},
year = {2024},
date = {2024-05-08},
urldate = {2024-05-08},
journal = {Phys. Rev. Lett.},
volume = {132},
number = {19},
pages = {196501},
abstract = {We report on time-resolved nonlinear terahertz spectroscopy of a strongly correlated ruthenate, CaRuO_{3}, as a function of temperature, frequency, and terahertz field strength. Third-harmonic radiation for frequencies up to 2.1 THz is observed evidently at low temperatures below 80 K, where the low-frequency linear dynamical response deviates from the Drude model and a coherent heavy quasiparticle band emerges by strong correlations associated with the Hund’s coupling. Phenomenologically, by taking an experimentally observed frequency-dependent scattering rate, the deviation of the field driven kinetics from the Drude behavior is reconciled in a time-dependent Boltzmann description, which allows an attribution of the observed third-harmonic generation to the terahertz field driven nonlinear kinetics of the heavy quasiparticles.},
keywords = {B1, B5},
pubstate = {published},
tppubtype = {article}
}
We report on time-resolved nonlinear terahertz spectroscopy of a strongly correlated ruthenate, CaRuO3, as a function of temperature, frequency, and terahertz field strength. Third-harmonic radiation for frequencies up to 2.1 THz is observed evidently at low temperatures below 80 K, where the low-frequency linear dynamical response deviates from the Drude model and a coherent heavy quasiparticle band emerges by strong correlations associated with the Hund’s coupling. Phenomenologically, by taking an experimentally observed frequency-dependent scattering rate, the deviation of the field driven kinetics from the Drude behavior is reconciled in a time-dependent Boltzmann description, which allows an attribution of the observed third-harmonic generation to the terahertz field driven nonlinear kinetics of the heavy quasiparticles. | |
Ebad-Allah, J.; Jiang, M. -C.; Borkenhagen, R.; Meggle, F.; Prodan, L.; Tsurkan, V.; Schilberth, F.; Guo, G. -Y.; Arita, R.; Kézsmárki, I.; Kuntscher, C. A. Optical anisotropy of the kagome magnet FeSn: Dominant role of excitations between kagome and Sn layers Journal Article Phys. Rev. B 109, L201106 (2024). @article{ebad-allah_optical_2024,
title = {Optical anisotropy of the kagome magnet FeSn: Dominant role of excitations between kagome and Sn layers},
author = {J. Ebad-Allah and M. -C. Jiang and R. Borkenhagen and F. Meggle and L. Prodan and V. Tsurkan and F. Schilberth and G. -Y. Guo and R. Arita and I. Kézsmárki and C. A. Kuntscher},
doi = {10.1103/PhysRevB.109.L201106},
year = {2024},
date = {2024-05-07},
urldate = {2024-05-01},
journal = {Phys. Rev. B},
volume = {109},
number = {20},
pages = {L201106},
abstract = {Antiferromagnetic FeSn is considered to be a close realization of the ideal two-dimensional (2D) kagome lattice, hosting Dirac cones, van Hove singularities, and flat bands, as it comprises Fe3Sn kagome layers well separated by Sn buffer layers. We observe a pronounced optical anisotropy, with the low-energy optical conductivity being surprisingly higher perpendicular to the kagome planes than along the layers. This finding contradicts the prevalent picture of dominantly 2D electronic structure for FeSn. Our material-specific theory reproduces the measured conductivity spectra remarkably well. A site-specific decomposition of the optical response to individual excitation channels shows that the optical conductivity for polarizations both parallel and perpendicular to the kagome plane is dominated by interlayer transitions between kagome layers and adjacent Sn-based layers. Moreover, the matrix elements corresponding to these transitions are highly anisotropic, leading to larger out-of-plane conductivity. Our results evidence the crucial role of interstitial layers in charge dynamics even in seemingly 2D systems.},
keywords = {A1},
pubstate = {published},
tppubtype = {article}
}
Antiferromagnetic FeSn is considered to be a close realization of the ideal two-dimensional (2D) kagome lattice, hosting Dirac cones, van Hove singularities, and flat bands, as it comprises Fe3Sn kagome layers well separated by Sn buffer layers. We observe a pronounced optical anisotropy, with the low-energy optical conductivity being surprisingly higher perpendicular to the kagome planes than along the layers. This finding contradicts the prevalent picture of dominantly 2D electronic structure for FeSn. Our material-specific theory reproduces the measured conductivity spectra remarkably well. A site-specific decomposition of the optical response to individual excitation channels shows that the optical conductivity for polarizations both parallel and perpendicular to the kagome plane is dominated by interlayer transitions between kagome layers and adjacent Sn-based layers. Moreover, the matrix elements corresponding to these transitions are highly anisotropic, leading to larger out-of-plane conductivity. Our results evidence the crucial role of interstitial layers in charge dynamics even in seemingly 2D systems. | |
Huber, N.; Mishra, S.; Sheikin, I.; Alpin, K.; Schnyder, A. P.; Benka, G.; Bauer, A.; Pfleiderer, C.; Wilde, M. A. Fermi surface of the chiral topological semimetal CoSi Journal Article Phys. Rev. B 109, 205115 (2024). @article{huber_fermi_2024,
title = {Fermi surface of the chiral topological semimetal CoSi},
author = {N. Huber and S. Mishra and I. Sheikin and K. Alpin and A. P. Schnyder and G. Benka and A. Bauer and C. Pfleiderer and M. A. Wilde},
doi = {10.1103/PhysRevB.109.205115},
year = {2024},
date = {2024-05-06},
urldate = {2024-05-01},
journal = {Phys. Rev. B},
volume = {109},
number = {20},
pages = {205115},
abstract = {We report a study of the Fermi surface of the chiral semimetal CoSi and its relationship to a network of multifold topological crossing points, Weyl points, and topological nodal planes in the electronic band structure. Combining quantum oscillations in the Hall resistivity, magnetization, and torque magnetization with ab initio electronic structure calculations, we identify two groups of Fermi-surface sheets, one centered at the 𝑅 point and the other centered at the Γ point. The presence of topological nodal planes at the Brillouin zone boundary enforces topological protectorates on the Fermi-surface sheets centered at the 𝑅 point. In addition, Weyl points exist close to the Fermi-surface sheets centered at the 𝑅 and the Γ points. In contrast, topological crossing points at the 𝑅 point and the Γ point, which have been advertised to feature exceptionally large Chern numbers, are located at a larger distance to the Fermi level. Representing a unique example in which the multitude of topological band crossings has been shown to form a complex network, our observations in CoSi highlight the need for detailed numerical calculations of the Berry curvature at the Fermi level, regardless of the putative existence and the possible character of topological band crossings in the band structure.},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
We report a study of the Fermi surface of the chiral semimetal CoSi and its relationship to a network of multifold topological crossing points, Weyl points, and topological nodal planes in the electronic band structure. Combining quantum oscillations in the Hall resistivity, magnetization, and torque magnetization with ab initio electronic structure calculations, we identify two groups of Fermi-surface sheets, one centered at the 𝑅 point and the other centered at the Γ point. The presence of topological nodal planes at the Brillouin zone boundary enforces topological protectorates on the Fermi-surface sheets centered at the 𝑅 point. In addition, Weyl points exist close to the Fermi-surface sheets centered at the 𝑅 and the Γ points. In contrast, topological crossing points at the 𝑅 point and the Γ point, which have been advertised to feature exceptionally large Chern numbers, are located at a larger distance to the Fermi level. Representing a unique example in which the multitude of topological band crossings has been shown to form a complex network, our observations in CoSi highlight the need for detailed numerical calculations of the Berry curvature at the Fermi level, regardless of the putative existence and the possible character of topological band crossings in the band structure. | |
Kosior, A.; Heyl, M. Vortex loop dynamics and dynamical quantum phase transitions in three-dimensional fermion matter Journal Article Phys. Rev. B 109, L140303 (2024). @article{kosior_vortex_2024,
title = {Vortex loop dynamics and dynamical quantum phase transitions in three-dimensional fermion matter},
author = {A. Kosior and M. Heyl},
doi = {10.1103/physrevb.109.l140303},
year = {2024},
date = {2024-04-15},
urldate = {2024-01-01},
journal = {Phys. Rev. B},
volume = {109},
number = {14},
pages = {L140303},
abstract = {Over the past decade, dynamical quantum phase transitions (DQPTs) have emerged as a paradigm shift in understanding nonequilibrium quantum many-body systems. However, the challenge lies in identifying order parameters that effectively characterize the associated dynamic phases. In this study we investigate the behavior of vortex singularities in the phase of the Green's function for a broad class of fermion lattice models in three dimensions after an instantaneous quench in both interacting and noninteracting systems. We find that the full set of vortices form one-dimensional dynamical objects, which we call vortex loops. We propose that the number of such vortex loops can be interpreted as a quantized order parameter that distinguishes between different nonequilibrium phases. Our results establish an explicit link between variations in the order parameter and DQPTs in the noninteracting scenario. Moreover, we show that the vortex loops are robust in the weakly interacting case, even though there is no direct relation between the Loschmidt amplitude and the Green's function. Finally, we observe that vortex loops can form complex dynamical patterns in momentum space. Our findings provide valuable insights for developing definitions of dynamical order parameters in nonequilibrium systems.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
Over the past decade, dynamical quantum phase transitions (DQPTs) have emerged as a paradigm shift in understanding nonequilibrium quantum many-body systems. However, the challenge lies in identifying order parameters that effectively characterize the associated dynamic phases. In this study we investigate the behavior of vortex singularities in the phase of the Green's function for a broad class of fermion lattice models in three dimensions after an instantaneous quench in both interacting and noninteracting systems. We find that the full set of vortices form one-dimensional dynamical objects, which we call vortex loops. We propose that the number of such vortex loops can be interpreted as a quantized order parameter that distinguishes between different nonequilibrium phases. Our results establish an explicit link between variations in the order parameter and DQPTs in the noninteracting scenario. Moreover, we show that the vortex loops are robust in the weakly interacting case, even though there is no direct relation between the Loschmidt amplitude and the Green's function. Finally, we observe that vortex loops can form complex dynamical patterns in momentum space. Our findings provide valuable insights for developing definitions of dynamical order parameters in nonequilibrium systems. | |
Luo, M.; Trivedi, R.; Bañuls, M. C.; Cirac, J. I. Probing off-diagonal eigenstate thermalization with tensor networks Journal Article Phys. Rev. B 109, 134304 (2024). @article{luo_probing_2024,
title = {Probing off-diagonal eigenstate thermalization with tensor networks},
author = {M. Luo and R. Trivedi and M. C. Bañuls and J. I. Cirac},
doi = {10.1103/PhysRevB.109.134304},
year = {2024},
date = {2024-04-08},
urldate = {2024-04-01},
journal = {Phys. Rev. B},
volume = {109},
number = {13},
pages = {134304},
keywords = {C5},
pubstate = {published},
tppubtype = {article}
}
| |
Boesl, J.; Zechmann, P.; Feldmeier, J.; Knap, M. Deconfinement Dynamics of Fractons in Tilted Bose-Hubbard Chains Journal Article Phys. Rev. Lett. 132, 143401 (2024). @article{boesl_deconfinement_2024,
title = {Deconfinement Dynamics of Fractons in Tilted Bose-Hubbard Chains},
author = {J. Boesl and P. Zechmann and J. Feldmeier and M. Knap},
doi = {10.1103/PhysRevLett.132.143401},
year = {2024},
date = {2024-04-01},
urldate = {2023-01-01},
journal = {Phys. Rev. Lett.},
volume = {132},
number = {14},
pages = {143401},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
| |
Jones, D.; Östlin, A.; Weh, A.; Beiuşeanu, F.; Eckern, U.; Vitos, L.; Chioncel, L. Superconducting transition temperatures of pure vanadium and vanadium-titanium alloys in the presence of dynamical electronic correlations Journal Article Phys. Rev. B 109, 165107 (2024). @article{jones_superconducting_2024,
title = {Superconducting transition temperatures of pure vanadium and vanadium-titanium alloys in the presence of dynamical electronic correlations},
author = {D. Jones and A. Östlin and A. Weh and F. Beiuşeanu and U. Eckern and L. Vitos and L. Chioncel},
doi = {10.1103/PhysRevB.109.165107},
year = {2024},
date = {2024-04-01},
urldate = {2024-04-12},
journal = {Phys. Rev. B},
volume = {109},
number = {16},
pages = {165107},
abstract = {Ordinary superconductors are widely assumed insensitive to small concentrations of random nonmagnetic impurities, whereas strong disorder suppresses superconductivity, ultimately leading to a superconductor-insulator transition. In between these limiting cases, a most fascinating regime may emerge where disorder enhances superconductivity. This effect is discussed here for the β phase of vanadium-titanium alloys. Disorder is modeled using the coherent potential approximation while local electronic interactions are treated using dynamical mean-field theory. The McMillan formula is employed to estimate the superconducting transition temperature, showing a maximum at a Ti concentration of around 0.33 for a local Coulomb interaction U in the range of 2 eV to 3 eV. Our calculations quantitatively agree with the experimentally observed concentration-dependent increase of Tc, and its maximal value of about 20%.},
keywords = {A5},
pubstate = {published},
tppubtype = {article}
}
Ordinary superconductors are widely assumed insensitive to small concentrations of random nonmagnetic impurities, whereas strong disorder suppresses superconductivity, ultimately leading to a superconductor-insulator transition. In between these limiting cases, a most fascinating regime may emerge where disorder enhances superconductivity. This effect is discussed here for the β phase of vanadium-titanium alloys. Disorder is modeled using the coherent potential approximation while local electronic interactions are treated using dynamical mean-field theory. The McMillan formula is employed to estimate the superconducting transition temperature, showing a maximum at a Ti concentration of around 0.33 for a local Coulomb interaction U in the range of 2 eV to 3 eV. Our calculations quantitatively agree with the experimentally observed concentration-dependent increase of Tc, and its maximal value of about 20%. | |
Solana-Madruga, E.; Mentre, O.; Tsirlin, A. A.; Huve, M.; Khalyavin, D.; Ritter, C.; Arevalo-Lopez, A. M. CoVO3 High-Pressure Polymorphs: To Order or Not to Order? Journal Article Adv. Sci. 11, 2307766 (2024). @article{solana-madruga_covo_3_2023,
title = {CoVO_{3} High-Pressure Polymorphs: To Order or Not to Order?},
author = {E. Solana-Madruga and O. Mentre and A. A. Tsirlin and M. Huve and D. Khalyavin and C. Ritter and A. M. Arevalo-Lopez},
doi = {10.1002/advs.202307766},
year = {2024},
date = {2024-03-06},
urldate = {2023-12-01},
journal = {Adv. Sci.},
volume = {11},
number = {9},
pages = {2307766},
abstract = {Materials properties are determined by their compositions and structures. In ABO(3) oxides different cation orderings lead to mainly perovskite- or corundum like derivatives with exciting physical properties. Sometimes, a material can be stabilized in more than one structural modification, providing a unique opportunity to explore structure-properties relationship. Here, CoVO3 obtained in both ilmenite-(CoVO3-I) and LiNbO3-type (CoVO3-II) polymorphs at moderate (8-12 GPa) and high pressures (22 GPa), respectively are presented. Their distinctive cation distributions affect drastically the magnetic properties as CoVO3-II shows a cluster-glass behavior while CoVO3-I hosts a honeycomb zigzag magnetic structure in the cobalt network. First principles calculations show that the influence of vanadium is crucial for CoVO3-I, although it is previously considered as non-magnetic in a dimerized spin-singlet state. Contrarily, CoVO3-II shows two independent interpenetrating antiferromagnetic Co- and ferromagnetic V-hcp sublattices, which intrinsically frustrate any possible magnetic order. CoVO3-II is also remarkable as the first oxide crystallizing with the LiNbO3-type structure where both metals contain free d electrons. CoVO3 polymorphs pinpoint therefore as well to a much broader phase field of high-pressure A-site Cobaltites.},
keywords = {B1, B3},
pubstate = {published},
tppubtype = {article}
}
Materials properties are determined by their compositions and structures. In ABO(3) oxides different cation orderings lead to mainly perovskite- or corundum like derivatives with exciting physical properties. Sometimes, a material can be stabilized in more than one structural modification, providing a unique opportunity to explore structure-properties relationship. Here, CoVO3 obtained in both ilmenite-(CoVO3-I) and LiNbO3-type (CoVO3-II) polymorphs at moderate (8-12 GPa) and high pressures (22 GPa), respectively are presented. Their distinctive cation distributions affect drastically the magnetic properties as CoVO3-II shows a cluster-glass behavior while CoVO3-I hosts a honeycomb zigzag magnetic structure in the cobalt network. First principles calculations show that the influence of vanadium is crucial for CoVO3-I, although it is previously considered as non-magnetic in a dimerized spin-singlet state. Contrarily, CoVO3-II shows two independent interpenetrating antiferromagnetic Co- and ferromagnetic V-hcp sublattices, which intrinsically frustrate any possible magnetic order. CoVO3-II is also remarkable as the first oxide crystallizing with the LiNbO3-type structure where both metals contain free d electrons. CoVO3 polymorphs pinpoint therefore as well to a much broader phase field of high-pressure A-site Cobaltites. | |
Zechmann, P.; Boesl, J.; Feldmeier, J.; Knap, M. Dynamical Spectral Response of Fractonic Quantum Matter Journal Article Phys. Rev. B 109, 125137 (2024). @article{zechmann_dynamical_2024,
title = {Dynamical Spectral Response of Fractonic Quantum Matter},
author = {P. Zechmann and J. Boesl and J. Feldmeier and M. Knap},
doi = {10.1103/physrevb.109.125137},
year = {2024},
date = {2024-03-01},
journal = {Phys. Rev. B},
volume = {109},
number = {12},
pages = {125137},
abstract = {Quantum many-body systems with fractonic excitations can realize fascinating phases of matter. Here, we study the low-energy excitations of a constrained Bose-Hubbard model in one dimension, which conserves the center of mass or, equivalently, the dipole moment in addition to the particle number. This model is known to realize fractonic phases, including a dipole Mott insulator, a dipole Luttinger liquid, and a metastable dipole supersolid. We use tensor network methods to compute spectral functions from the dynamical response of the system and verify predictions from low-energy field theories of the corresponding ground-state phases. We demonstrate the existence of gapped excitations compatible with strong coupling results in a dipole Mott insulator, linear sound modes characteristic of a Luttinger liquid of dipoles, and soft quadratic modes at both zero and finite momenta in a supersolid state with charge density wave order and phase coherence at noninteger filling.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quantum many-body systems with fractonic excitations can realize fascinating phases of matter. Here, we study the low-energy excitations of a constrained Bose-Hubbard model in one dimension, which conserves the center of mass or, equivalently, the dipole moment in addition to the particle number. This model is known to realize fractonic phases, including a dipole Mott insulator, a dipole Luttinger liquid, and a metastable dipole supersolid. We use tensor network methods to compute spectral functions from the dynamical response of the system and verify predictions from low-energy field theories of the corresponding ground-state phases. We demonstrate the existence of gapped excitations compatible with strong coupling results in a dipole Mott insulator, linear sound modes characteristic of a Luttinger liquid of dipoles, and soft quadratic modes at both zero and finite momenta in a supersolid state with charge density wave order and phase coherence at noninteger filling. | |
Choi, W.; Knap, M.; Pollmann, F. Finite Temperature Entanglement Negativity of Fermionic Symmetry Protected Topological Phases and Quantum Critical Points in One Dimension Journal Article Phys. Rev. B 109, 115132 (2024). @article{choi_finite_2024,
title = {Finite Temperature Entanglement Negativity of Fermionic Symmetry Protected Topological Phases and Quantum Critical Points in One Dimension},
author = {W. Choi and M. Knap and F. Pollmann},
doi = {10.1103/PhysRevB.109.115132},
year = {2024},
date = {2024-03-01},
urldate = {2023-01-01},
journal = {Phys. Rev. B},
volume = {109},
number = {11},
pages = {115132},
keywords = {C5},
pubstate = {published},
tppubtype = {article}
}
|  |
d'Ornellas, P.; Knolle, J. Kitaev-Heisenberg model on the star lattice: From chiral Majorana fermions to chiral triplons Journal Article Phys. Rev. B 109, 094421 (2024). @article{dornellas_kitaev-heisenberg_2024,
title = {Kitaev-Heisenberg model on the star lattice: From chiral Majorana fermions to chiral triplons},
author = {P. d'Ornellas and J. Knolle},
doi = {10.1103/PhysRevB.109.094421},
year = {2024},
date = {2024-03-01},
urldate = {2024-04-12},
journal = {Phys. Rev. B},
volume = {109},
number = {9},
pages = {094421},
abstract = {The interplay of frustrated interactions and lattice geometry can lead to a variety of exotic quantum phases. Here we unearth a particularly rich phase diagram of the Kitaev-Heisenberg model on the star lattice, a triangle decorated honeycomb lattice breaking sublattice symmetry. In the antiferromagnetic regime, the interplay of Heisenberg coupling and geometric frustration leads to the formation of valence bond solid (VBS) phases—a singlet VBS and a bond selective triplet VBS stabilized by the Kitaev exchange. We show that the ratio of the Kitaev versus Heisenberg exchange tunes between these VBS phases and chiral quantum spin-liquid regimes. Remarkably, the VBS phases host a whole variety of chiral triplon excitations with high Chern numbers in the presence of a weak magnetic field. We discuss our results in light of a recently synthesized star lattice material and other decorated lattice systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The interplay of frustrated interactions and lattice geometry can lead to a variety of exotic quantum phases. Here we unearth a particularly rich phase diagram of the Kitaev-Heisenberg model on the star lattice, a triangle decorated honeycomb lattice breaking sublattice symmetry. In the antiferromagnetic regime, the interplay of Heisenberg coupling and geometric frustration leads to the formation of valence bond solid (VBS) phases—a singlet VBS and a bond selective triplet VBS stabilized by the Kitaev exchange. We show that the ratio of the Kitaev versus Heisenberg exchange tunes between these VBS phases and chiral quantum spin-liquid regimes. Remarkably, the VBS phases host a whole variety of chiral triplon excitations with high Chern numbers in the presence of a weak magnetic field. We discuss our results in light of a recently synthesized star lattice material and other decorated lattice systems. | |
Shen, B.; Ginga, V. A.; Arévalo-López, A. M.; Garbarino, G.; Uykur, E.; Goncalves-Faria, M.; Mukharjee, P. K.; Gegenwart, P.; Tsirlin, A. A. Magnetic vs. nonmagnetic polymorphs of RuBr3 under pressure Journal Article Phys. Rev. B 109, 224402 (2024). @article{shen_magnetic_2024,
title = {Magnetic vs. nonmagnetic polymorphs of RuBr_{3} under pressure},
author = {B. Shen and V. A. Ginga and A. M. Arévalo-López and G. Garbarino and E. Uykur and M. Goncalves-Faria and P. K. Mukharjee and P. Gegenwart and A. A. Tsirlin},
doi = {10.1103/PhysRevB.109.224402},
year = {2024},
date = {2024-03-01},
urldate = {2024-03-01},
journal = {Phys. Rev. B},
volume = {109},
number = {22},
pages = {224402},
abstract = {Pressure evolution of the crystal structure and magnetism of the honeycomb 𝛼-RuBr_3 is studied using high-pressure x-ray diffraction, magnetometry, and density-functional band-structure calculations. Hydrostatic compression transforms antiferromagnetic 𝛼-RuBr_3 (R-3) into paramagnetic 𝛼'-RuBr_3 (P-1) where short Ru-Ru bonds cause magnetism collapse above 1.3 GPa at 0 K and 2.5 GPa at 295 K. Below this critical pressure, the Ntextbackslash'eel temperature of 𝛼-RuBr_3 increases with the slope of 1.8 K/GPa. Pressure tunes 𝛼-RuBr_3 away from the Kitaev limit, whereas increased third-neighbor in-plane coupling and interlayer coupling lead to a further stabilization of the collinear zigzag state. Both 𝛼- and 𝛼'-RuBr_3 are metastable at ambient pressure, but their transformation into the thermodynamically stable 𝛽-polymorph is kinetically hindered at room temperature.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
Pressure evolution of the crystal structure and magnetism of the honeycomb 𝛼-RuBr_3 is studied using high-pressure x-ray diffraction, magnetometry, and density-functional band-structure calculations. Hydrostatic compression transforms antiferromagnetic 𝛼-RuBr_3 (R-3) into paramagnetic 𝛼'-RuBr_3 (P-1) where short Ru-Ru bonds cause magnetism collapse above 1.3 GPa at 0 K and 2.5 GPa at 295 K. Below this critical pressure, the Ntextbackslash'eel temperature of 𝛼-RuBr_3 increases with the slope of 1.8 K/GPa. Pressure tunes 𝛼-RuBr_3 away from the Kitaev limit, whereas increased third-neighbor in-plane coupling and interlayer coupling lead to a further stabilization of the collinear zigzag state. Both 𝛼- and 𝛼'-RuBr_3 are metastable at ambient pressure, but their transformation into the thermodynamically stable 𝛽-polymorph is kinetically hindered at room temperature. | |
Kadow, W.; Jin, H. -K.; Knolle, J.; Knap, M. Single-hole spectra of Kitaev spin liquids: From dynamical Nagaoka ferromagnetism to spin-hole fractionalization Journal Article npj Quantum Mater. 9, 32 (2024). @article{kadow_single-hole_2024,
title = {Single-hole spectra of Kitaev spin liquids: From dynamical Nagaoka ferromagnetism to spin-hole fractionalization},
author = {W. Kadow and H. -K. Jin and J. Knolle and M. Knap},
url = {https://doi.org/10.1038/s41535-024-00641-7},
doi = {10.1038/s41535-024-00641-7},
year = {2024},
date = {2024-03-01},
urldate = {2024-03-01},
journal = {npj Quantum Mater.},
volume = {9},
number = {1},
pages = {32},
abstract = {The dynamical response of a quantum spin liquid upon injecting a hole is a pertinent open question. In experiments, the hole spectral function, measured momentum-resolved in angle-resolved photoemission spectroscopy (ARPES) or locally in scanning tunneling microscopy (STM), can be used to identify spin liquid materials. In this study, we employ tensor network methods to simulate the time evolution of a single hole doped into the Kitaev spin-liquid ground state. Focusing on the gapped spin liquid phase, we reveal two fundamentally different scenarios. For ferromagnetic spin couplings, the spin liquid is highly susceptible to hole doping: a Nagaoka ferromagnet forms dynamically around the doped hole, even at weak coupling. By contrast, in the case of antiferromagnetic spin couplings, the hole spectrum demonstrates an intricate interplay between charge, spin, and flux degrees of freedom, best described by a parton mean-field ansatz of fractionalized holons and spinons. Moreover, we find a good agreement of our numerical results to the analytically solvable case of slow holes. Our results demonstrate that dynamical hole spectral functions provide rich information on the structure of fractionalized quantum spin liquids.},
keywords = {B6},
pubstate = {published},
tppubtype = {article}
}
The dynamical response of a quantum spin liquid upon injecting a hole is a pertinent open question. In experiments, the hole spectral function, measured momentum-resolved in angle-resolved photoemission spectroscopy (ARPES) or locally in scanning tunneling microscopy (STM), can be used to identify spin liquid materials. In this study, we employ tensor network methods to simulate the time evolution of a single hole doped into the Kitaev spin-liquid ground state. Focusing on the gapped spin liquid phase, we reveal two fundamentally different scenarios. For ferromagnetic spin couplings, the spin liquid is highly susceptible to hole doping: a Nagaoka ferromagnet forms dynamically around the doped hole, even at weak coupling. By contrast, in the case of antiferromagnetic spin couplings, the hole spectrum demonstrates an intricate interplay between charge, spin, and flux degrees of freedom, best described by a parton mean-field ansatz of fractionalized holons and spinons. Moreover, we find a good agreement of our numerical results to the analytically solvable case of slow holes. Our results demonstrate that dynamical hole spectral functions provide rich information on the structure of fractionalized quantum spin liquids. | |
Wang, L.; Liu, H.; Zimmermann, V.; Yogi, A. K.; Isobe, M.; Minola, M.; Hepting, M.; Khaliullin, G.; Keimer, B. Spin-Orbit Excitons in a Correlated Metal: Raman Scattering Study of Sr2RhO4 Journal Article Phys. Rev. Lett. 132, 116502 (2024). @article{wang_spin-orbit_2024,
title = {Spin-Orbit Excitons in a Correlated Metal: Raman Scattering Study of Sr_{2}RhO_{4}},
author = {L. Wang and H. Liu and V. Zimmermann and A. K. Yogi and M. Isobe and M. Minola and M. Hepting and G. Khaliullin and B. Keimer},
doi = {10.1103/PhysRevLett.132.116502},
year = {2024},
date = {2024-03-01},
urldate = {2024-03-01},
journal = {Phys. Rev. Lett.},
volume = {132},
number = {11},
pages = {116502},
abstract = {Using Raman spectroscopy to study the correlated 4d-electron metal Sr2RhO4, we observe pronounced excitations at 220 meV and 240 meV with A1g and B1g symmetries, respectively. We identify them as transitions between the spin-orbit multiplets of the Rh ions, in close analogy to the spin-orbit excitons in the Mott insulators Sr2IrO4 and α−RuCl3. This observation provides direct evidence for the unquenched spin-orbit coupling in Sr2RhO4. A quantitative analysis of the data reveals that the tetragonal crystal field Δ in Sr2RhO4 has a sign opposite to that in insulating Sr2IrO4, which enhances the planar xy orbital character of the effective J=1/2 wave function. This supports a metallic ground state, and suggests that c-axis compression of Sr2RhO4 may transform it into a quasi-two-dimensional antiferromagnetic insulator.},
keywords = {B2},
pubstate = {published},
tppubtype = {article}
}
Using Raman spectroscopy to study the correlated 4d-electron metal Sr2RhO4, we observe pronounced excitations at 220 meV and 240 meV with A1g and B1g symmetries, respectively. We identify them as transitions between the spin-orbit multiplets of the Rh ions, in close analogy to the spin-orbit excitons in the Mott insulators Sr2IrO4 and α−RuCl3. This observation provides direct evidence for the unquenched spin-orbit coupling in Sr2RhO4. A quantitative analysis of the data reveals that the tetragonal crystal field Δ in Sr2RhO4 has a sign opposite to that in insulating Sr2IrO4, which enhances the planar xy orbital character of the effective J=1/2 wave function. This supports a metallic ground state, and suggests that c-axis compression of Sr2RhO4 may transform it into a quasi-two-dimensional antiferromagnetic insulator. | |
Müller, M.; Weber, J.; Engelhardt, F.; Bittencourt, V. A. S. V.; Luschmann, T.; Cherkasskii, M.; Opel, M.; Goennenwein, S. T. B.; Kusminskiy, S. V.; Geprägs, S.; Gross, R.; Althammer, M.; Huebl, H. Chiral phonons and phononic birefringence in ferromagnetic metal–bulk acoustic resonator hybrids Journal Article Phys. Rev. B 109, 024430 (2024). @article{muller_chiral_2024,
title = {Chiral phonons and phononic birefringence in ferromagnetic metal–bulk acoustic resonator hybrids},
author = {M. Müller and J. Weber and F. Engelhardt and V. A. S. V. Bittencourt and T. Luschmann and M. Cherkasskii and M. Opel and S. T. B. Goennenwein and S. V. Kusminskiy and S. Geprägs and R. Gross and M. Althammer and H. Huebl},
doi = {10.1103/PhysRevB.109.024430},
year = {2024},
date = {2024-01-23},
urldate = {2024-01-01},
journal = {Phys. Rev. B},
volume = {109},
number = {2},
pages = {024430},
abstract = {Magnomechanical devices, in which magnetic excitations couple to mechanical vibrations, have been discussed as efficient and broadband microwave signal transducers in the classical and quantum limit. We experimentally investigate the resonant magnetoelastic coupling between the ferromagnetic resonance modes in metallic Co25Fe75 thin films, featuring ultralow magnetic damping as well as sizable magnetostriction, and standing transverse elastic phonon modes in sapphire, silicon, and gadolinium gallium garnet at cryogenic temperatures. For all substrates, we observe a coherent interaction between the acoustic and magnetic modes. We identify the phonon modes as transverse shear waves propagating with slightly different velocities (Δv/v≃10−5); i.e., all investigated substrates show potential for phononic birefringence as well as phonon-mediated angular momentum transport. Our magnon-phonon hybrid systems operate in a coupling regime analogous to the Purcell enhanced damping in cavity magnonics.},
keywords = {C3},
pubstate = {published},
tppubtype = {article}
}
Magnomechanical devices, in which magnetic excitations couple to mechanical vibrations, have been discussed as efficient and broadband microwave signal transducers in the classical and quantum limit. We experimentally investigate the resonant magnetoelastic coupling between the ferromagnetic resonance modes in metallic Co25Fe75 thin films, featuring ultralow magnetic damping as well as sizable magnetostriction, and standing transverse elastic phonon modes in sapphire, silicon, and gadolinium gallium garnet at cryogenic temperatures. For all substrates, we observe a coherent interaction between the acoustic and magnetic modes. We identify the phonon modes as transverse shear waves propagating with slightly different velocities (Δv/v≃10−5); i.e., all investigated substrates show potential for phononic birefringence as well as phonon-mediated angular momentum transport. Our magnon-phonon hybrid systems operate in a coupling regime analogous to the Purcell enhanced damping in cavity magnonics. | |
Wu, X.; Chakraborty, D.; Schnyder, A. P.; Greco, A. Crossover between electron-electron and electron-phonon mediated pairing on the Kagome lattice Journal Article Phys. Rev. B 109, 014517 (2024). @article{wu_crossover_2024,
title = {Crossover between electron-electron and electron-phonon mediated pairing on the Kagome lattice},
author = {X. Wu and D. Chakraborty and A. P. Schnyder and A. Greco},
doi = {10.1103/physrevb.109.014517},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {Phys. Rev. B},
volume = {109},
number = {1},
pages = {014517},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
|  |
Romen, A.; Birnkammer, S.; Knap, M. Deconfined quantum criticality in the long-range, anisotropic Heisenberg chain Journal Article SciPost Phys. Core 7, 008 (2024). @article{romen_deconfined_2024,
title = {Deconfined quantum criticality in the long-range, anisotropic Heisenberg chain},
author = {A. Romen and S. Birnkammer and M. Knap},
doi = {10.21468/scipostphyscore.7.1.008},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {SciPost Phys. Core},
volume = {7},
number = {1},
pages = {008},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
| |
Zhao, K.; Tokiwa, Y.; Chen, H.; Gegenwart, P. Discrete degeneracies distinguished by the anomalous Hall effect in a metallic kagome ice compound Journal Article Nat. Phys. 20, 442 (2024). @article{zhao_discrete_2024,
title = {Discrete degeneracies distinguished by the anomalous Hall effect in a metallic kagome ice compound},
author = {K. Zhao and Y. Tokiwa and H. Chen and P. Gegenwart},
doi = {10.1038/s41567-023-02307-w},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {Nat. Phys.},
volume = {20},
pages = {442},
abstract = {In magnetic crystals, despite the explicit breaking of time-reversal symmetry, two equilibrium states related by time reversal are always energetically degenerate. In ferromagnets, this time-reversal degeneracy is reflected in the hysteresis of the magnetic field dependence of the magnetization and, if metallic, in that of the anomalous Hall effect (AHE). Under time-reversal, both these quantities change signs but not their magnitude. Here we show that a time-reversal-like degeneracy appears in the metallic kagome spin ice HoAgGe when magnetic fields are applied parallel to the kagome plane. We find vanishing hysteresis in the field dependence of the magnetization at low temperature, but finite hysteresis in the field-dependent AHE. This suggests the emergence of states with nearly the same energy and net magnetization but different sizes of the AHE and of the longitudinal magnetoresistance. By analysing the experimental data and a minimal tight-binding model, we identify a time-reversal-like operation connecting these near-degenerate states, which is related to the non-trivial distortion of the kagome lattice in HoAgGe. Our work demonstrates the diagnostic power of transport phenomena for identifying hidden symmetries in frustrated spin systems. Transport measurements of the metallic kagome spin ice HoAgGe show that it has an emergent discrete symmetry that is not apparent from measurements of its magnetization.},
keywords = {B3},
pubstate = {published},
tppubtype = {article}
}
In magnetic crystals, despite the explicit breaking of time-reversal symmetry, two equilibrium states related by time reversal are always energetically degenerate. In ferromagnets, this time-reversal degeneracy is reflected in the hysteresis of the magnetic field dependence of the magnetization and, if metallic, in that of the anomalous Hall effect (AHE). Under time-reversal, both these quantities change signs but not their magnitude. Here we show that a time-reversal-like degeneracy appears in the metallic kagome spin ice HoAgGe when magnetic fields are applied parallel to the kagome plane. We find vanishing hysteresis in the field dependence of the magnetization at low temperature, but finite hysteresis in the field-dependent AHE. This suggests the emergence of states with nearly the same energy and net magnetization but different sizes of the AHE and of the longitudinal magnetoresistance. By analysing the experimental data and a minimal tight-binding model, we identify a time-reversal-like operation connecting these near-degenerate states, which is related to the non-trivial distortion of the kagome lattice in HoAgGe. Our work demonstrates the diagnostic power of transport phenomena for identifying hidden symmetries in frustrated spin systems. Transport measurements of the metallic kagome spin ice HoAgGe show that it has an emergent discrete symmetry that is not apparent from measurements of its magnetization. | |
Kutko, K.; Bernáth, B.; Khrustalyov, V.; Young, O.; Engelkamp, H.; Christianen, P. C. M.; Prodan, L.; Skourski, Y.; Pourovskii, L. V.; Khmelevskyi, S.; Kamenskyi, D. High-field magnetization of KEr(MoO4)2 Journal Article Phys. Rev. B 109, 024438 (2024). @article{kutko_high-field_2024,
title = {High-field magnetization of KEr(MoO_{4})_{2}},
author = {K. Kutko and B. Bernáth and V. Khrustalyov and O. Young and H. Engelkamp and P. C. M. Christianen and L. Prodan and Y. Skourski and L. V. Pourovskii and S. Khmelevskyi and D. Kamenskyi},
doi = {10.1103/PhysRevB.109.024438},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {Phys. Rev. B},
volume = {109},
number = {2},
pages = {024438},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
| |
Leeb, V.; Knolle, J. Interband scattering-and nematicity-induced quantum oscillation frequency in FeSe Journal Article Phys. Rev. B 109, L081109 (2024). @article{leeb_interband_2024,
title = {Interband scattering-and nematicity-induced quantum oscillation frequency in FeSe},
author = {V. Leeb and J. Knolle},
doi = {10.1103/physrevb.109.l081109},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {Phys. Rev. B},
volume = {109},
number = {8},
pages = {L081109},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
| |
Hu, Y.; Ma, J.; Li, Y.; Jiang, Y.; Gawryluk, D. J.; Hu, T.; Teyssier, J.; Multian, V.; Yin, Z.; Xu, S.; others, Phonon promoted charge density wave in topological kagome metal ScV6Sn6 Journal Article Nat. Commun. 15, 1658 (2024). @article{hu_phonon_2024,
title = {Phonon promoted charge density wave in topological kagome metal ScV_{6}Sn_{6}},
author = {Y. Hu and J. Ma and Y. Li and Y. Jiang and D. J. Gawryluk and T. Hu and J. Teyssier and V. Multian and Z. Yin and S. Xu and others},
doi = {10.1038/s41467-024-45859-y},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {Nat. Commun.},
volume = {15},
number = {1},
pages = {1658},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
| |
Simeth, W.; Rahn, M. C.; Bauer, A.; Meven, M.; Pfleiderer, C. Topological aspects of multi-k antiferromagnetism in cubic rare-earth compounds Journal Article J. Phys.: Condens. Matter 36, 215602 (2024). @article{simeth_topological_2024,
title = {Topological aspects of multi-k antiferromagnetism in cubic rare-earth compounds},
author = {W. Simeth and M. C. Rahn and A. Bauer and M. Meven and C. Pfleiderer},
doi = {10.1088/1361-648x/ad24bb},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {J. Phys.: Condens. Matter},
volume = {36},
number = {21},
pages = {215602},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
| |
Alpin, K. Perturbative description of high-Tc superconductivity in the Hubbard model via unitary transformation and classical spins Unpublished (2024), arXiv.2403.09765. @unpublished{alpin_perturbative_2024,
title = {Perturbative description of high-T_{c} superconductivity in the Hubbard model via unitary transformation and classical spins},
author = {K. Alpin},
doi = {10.48550/arXiv.2403.09765},
year = {2024},
date = {2024-03-14},
urldate = {2024-03-01},
abstract = {A unitary transformation is applied to the Hubbard model, which maps the Hubbard interaction to a single particle term. The resulting Hamiltonian consists of unconstrained fermions, which is then mapped to a Hamiltonian of spinless fermions coupled to pseudospins. The fermions are integrated out using second order perturbation theory in $1/U$, resulting in an effective spin Hamiltonian. An order parameter is identified, stabilizing d-wave superconductivity. The groundstate energy of classical spin configurations is minimized at a finite value of this order parameter after a critical chemical potential, resulting in d-wave superconductivity at non-zero doping. This suggests, that the onset of high-$T_c$ superconductivity is governed by the groundstate of a classical spin system.},
note = {arXiv.2403.09765},
keywords = {A6},
pubstate = {published},
tppubtype = {unpublished}
}
A unitary transformation is applied to the Hubbard model, which maps the Hubbard interaction to a single particle term. The resulting Hamiltonian consists of unconstrained fermions, which is then mapped to a Hamiltonian of spinless fermions coupled to pseudospins. The fermions are integrated out using second order perturbation theory in $1/U$, resulting in an effective spin Hamiltonian. An order parameter is identified, stabilizing d-wave superconductivity. The groundstate energy of classical spin configurations is minimized at a finite value of this order parameter after a critical chemical potential, resulting in d-wave superconductivity at non-zero doping. This suggests, that the onset of high-$T_c$ superconductivity is governed by the groundstate of a classical spin system. | |
2023
|
Panther, A.; Tsirlin, A. A.; Rousochatzakis, I. Frustration relief and reorientation transition in the kagomelike dolerophanite Cu2OSO4 Journal Article Phys. Rev. B 108, 224410 (2023). @article{panther_frustration_2023,
title = {Frustration relief and reorientation transition in the kagomelike dolerophanite Cu_{2}OSO_{4}},
author = {A. Panther and A. A. Tsirlin and I. Rousochatzakis},
doi = {10.1103/PhysRevB.108.224410},
year = {2023},
date = {2023-12-01},
urldate = {2023-12-01},
journal = {Phys. Rev. B},
volume = {108},
number = {22},
pages = {224410},
abstract = {We present a theoretical study of dolerophanite Cu2OSO4, a layered kagomelike spin-21 magnetic insulator that can be described either as a system of chains coupled through dimers or as a kagome lattice where every third spin is replaced by a ferromagnetic spin dimer. Building on insights from ab initio calculations, classical numerical minimizations, and semiclassical expansions, we arrive at a minimal microscopic description that accounts for the experimental data reported so far, including the nature of the magnetic order, the reported spin length, and the observed anisotropy. The latter arises by a peculiar competition between the antisymmetric (DzyaloshinskiiMoriya) and the symmetric part of the exchange anisotropy, which gives rise to a two-step reorientation process involving two successive continuous phase transitions. In this paper, we uncover mechanisms stabilizing canted ferrimagnetic order in kagome systems and highlight strong magnetic anisotropy in the presence of dissimilar magnetic orbitals on crystallographically nonequivalent Cu sites. We also show how these anisotropy terms affect the spin-wave spectrum and how they can be tracked experimentally.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
We present a theoretical study of dolerophanite Cu2OSO4, a layered kagomelike spin-21 magnetic insulator that can be described either as a system of chains coupled through dimers or as a kagome lattice where every third spin is replaced by a ferromagnetic spin dimer. Building on insights from ab initio calculations, classical numerical minimizations, and semiclassical expansions, we arrive at a minimal microscopic description that accounts for the experimental data reported so far, including the nature of the magnetic order, the reported spin length, and the observed anisotropy. The latter arises by a peculiar competition between the antisymmetric (DzyaloshinskiiMoriya) and the symmetric part of the exchange anisotropy, which gives rise to a two-step reorientation process involving two successive continuous phase transitions. In this paper, we uncover mechanisms stabilizing canted ferrimagnetic order in kagome systems and highlight strong magnetic anisotropy in the presence of dissimilar magnetic orbitals on crystallographically nonequivalent Cu sites. We also show how these anisotropy terms affect the spin-wave spectrum and how they can be tracked experimentally. | |
Breitner, F. A.; Kaiser, J.; Jesche, A.; Gegenwart, P. Metallic conductivity in Na-deficient structural domain walls in the spin-orbit Mott insulator Na2IrO3 Journal Article Phys. Rev. B 108, 235130 (2023). @article{breitner_metallic_2023,
title = {Metallic conductivity in Na-deficient structural domain walls in the spin-orbit Mott insulator Na_{2}IrO_{3}},
author = {F. A. Breitner and J. Kaiser and A. Jesche and P. Gegenwart},
doi = {10.1103/PhysRevB.108.235130},
year = {2023},
date = {2023-12-01},
urldate = {2023-12-01},
journal = {Phys. Rev. B},
volume = {108},
number = {23},
pages = {235130},
abstract = {Honeycomb Na2IrO3 is a prototype spin-orbit Mott insulator and Kitaev magnet. We report a combined structural and electrical resistivity study of Na2IrO3 single crystals. Laue back-scattering diffraction indicates twinning with +/- 120 degrees rotation around the c* axis while scanning electron microscopy displays nanothin lines parallel to all three b-axis orientations of twin domains. Energy dispersive x-ray analysis line scans across such domain walls indicate no change of the Ir signal intensity, i.e., intact honeycomb layers, while the Na intensity is reduced down to similar to 2/3 of its original value at the domain walls, implying significant hole doping. Utilizing focused-ion-beam microsectioning, the temperature dependence of the electrical resistance of individual domain walls is studied. It demonstrates the tuning through the metal-insulator transition into a correlated-metal ground state by increasing hole doping.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
Honeycomb Na2IrO3 is a prototype spin-orbit Mott insulator and Kitaev magnet. We report a combined structural and electrical resistivity study of Na2IrO3 single crystals. Laue back-scattering diffraction indicates twinning with +/- 120 degrees rotation around the c* axis while scanning electron microscopy displays nanothin lines parallel to all three b-axis orientations of twin domains. Energy dispersive x-ray analysis line scans across such domain walls indicate no change of the Ir signal intensity, i.e., intact honeycomb layers, while the Na intensity is reduced down to similar to 2/3 of its original value at the domain walls, implying significant hole doping. Utilizing focused-ion-beam microsectioning, the temperature dependence of the electrical resistance of individual domain walls is studied. It demonstrates the tuning through the metal-insulator transition into a correlated-metal ground state by increasing hole doping. | |
Alpin, K.; Hirschmann, M. M.; Heinsdorf, N.; Leonhardt, A.; Yau, W. Y.; Wu, X.; Schnyder, A. P. Fundamental laws of chiral band crossings: Local constraints, global constraints, and topological phase diagrams Journal Article Phys. Rev. Research 5, 043165 (2023). @article{alpin_fundamental_2023,
title = {Fundamental laws of chiral band crossings: Local constraints, global constraints, and topological phase diagrams},
author = {K. Alpin and M. M. Hirschmann and N. Heinsdorf and A. Leonhardt and W. Y. Yau and X. Wu and A. P. Schnyder},
doi = {10.1103/PhysRevResearch.5.043165},
year = {2023},
date = {2023-11-01},
urldate = {2023-11-01},
journal = {Phys. Rev. Research},
volume = {5},
number = {4},
pages = {043165},
abstract = {We derive two fundamental laws of chiral band crossings: (i) a local constraint relating the Chern number to phase jumps of rotation eigenvalues and (ii) a global constraint determining the number of chiral crossings on rotation axes. Together with the fermion doubling theorem, these laws describe all conditions that a network of chiral band crossing must satisfy. We apply the fundamental laws to prove the existence of enforced double Weyl points, nodal planes, and generic Weyl points, among others. In addition, we show that chiral space group symmetries can not stabilize nodal lines with finite Chern numbers. Combining the local constraint with explicit low-energy models, we determine the generic topological phase diagrams of all multifold crossings. Remarkably, we find a fourfold crossing with Chern number 5, which exceeds the previously conceived maximum Chern number of 4. We identify materials crystallizing in space group 198, such as B20 materials and BaAsPt, as suitable compounds with this Chern number 5 crossing.},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
We derive two fundamental laws of chiral band crossings: (i) a local constraint relating the Chern number to phase jumps of rotation eigenvalues and (ii) a global constraint determining the number of chiral crossings on rotation axes. Together with the fermion doubling theorem, these laws describe all conditions that a network of chiral band crossing must satisfy. We apply the fundamental laws to prove the existence of enforced double Weyl points, nodal planes, and generic Weyl points, among others. In addition, we show that chiral space group symmetries can not stabilize nodal lines with finite Chern numbers. Combining the local constraint with explicit low-energy models, we determine the generic topological phase diagrams of all multifold crossings. Remarkably, we find a fourfold crossing with Chern number 5, which exceeds the previously conceived maximum Chern number of 4. We identify materials crystallizing in space group 198, such as B20 materials and BaAsPt, as suitable compounds with this Chern number 5 crossing. | |
Ghara, S.; Barts, E.; Vasin, K. V.; Kamenskyi, D.; Prodan, L.; Tsurkan, V.; Kézsmárki, I.; Mostovoy, M.; Deisenhofer, J. Magnetization reversal through an antiferromagnetic state Journal Article Nat. Commun. 14, 5174 (2023). @article{ghara_magnetization_2023,
title = {Magnetization reversal through an antiferromagnetic state},
author = {S. Ghara and E. Barts and K. V. Vasin and D. Kamenskyi and L. Prodan and V. Tsurkan and I. Kézsmárki and M. Mostovoy and J. Deisenhofer},
doi = {10.1038/s41467-023-40722-y},
year = {2023},
date = {2023-08-01},
urldate = {2023-08-01},
journal = {Nat. Commun.},
volume = {14},
number = {1},
pages = {5174},
abstract = {Magnetization reversal in ferro- and ferrimagnets is a well-known archetype of non-equilibrium processes, where the volume fractions of the oppositely magnetized domains vary and perfectly compensate each other at the coercive magnetic field. Here, we report on a fundamentally new pathway for magnetization reversal that is mediated by an antiferromagnetic state. Consequently, an atomic-scale compensation of the magnetization is realized at the coercive field, instead of the mesoscopic or macroscopic domain cancellation in canonical reversal processes. We demonstrate this unusual magnetization reversal on the Zn-doped polar magnet Fe2Mo3O8. Hidden behind the conventional ferrimagnetic hysteresis loop, the surprising emergence of the antiferromagnetic phase at the coercive fields is disclosed by a sharp peak in the field-dependence of the electric polarization. In addition, at the magnetization reversal our THz spectroscopy studies reveal the reappearance of the magnon mode that is only present in the pristine antiferromagnetic state. According to our microscopic calculations, this unusual process is governed by the dominant intralayer coupling, strong easy-axis anisotropy and spin fluctuations, which result in a complex interplay between the ferrimagnetic and antiferromagnetic phases. Such antiferro-state-mediated reversal processes offer novel concepts for magnetization control, and may also emerge for other ferroic orders.},
keywords = {A1, C4},
pubstate = {published},
tppubtype = {article}
}
Magnetization reversal in ferro- and ferrimagnets is a well-known archetype of non-equilibrium processes, where the volume fractions of the oppositely magnetized domains vary and perfectly compensate each other at the coercive magnetic field. Here, we report on a fundamentally new pathway for magnetization reversal that is mediated by an antiferromagnetic state. Consequently, an atomic-scale compensation of the magnetization is realized at the coercive field, instead of the mesoscopic or macroscopic domain cancellation in canonical reversal processes. We demonstrate this unusual magnetization reversal on the Zn-doped polar magnet Fe2Mo3O8. Hidden behind the conventional ferrimagnetic hysteresis loop, the surprising emergence of the antiferromagnetic phase at the coercive fields is disclosed by a sharp peak in the field-dependence of the electric polarization. In addition, at the magnetization reversal our THz spectroscopy studies reveal the reappearance of the magnon mode that is only present in the pristine antiferromagnetic state. According to our microscopic calculations, this unusual process is governed by the dominant intralayer coupling, strong easy-axis anisotropy and spin fluctuations, which result in a complex interplay between the ferrimagnetic and antiferromagnetic phases. Such antiferro-state-mediated reversal processes offer novel concepts for magnetization control, and may also emerge for other ferroic orders. |  |
Huber, N.; Leeb, V.; Bauer, A.; Benka, G.; Knolle, J.; Pfleiderer, C.; Wilde, M. A. Quantum oscillations of the quasiparticle lifetime in a metal Journal Article Nature 621, 276 (2023). @article{huber_quantum_2023,
title = {Quantum oscillations of the quasiparticle lifetime in a metal},
author = {N. Huber and V. Leeb and A. Bauer and G. Benka and J. Knolle and C. Pfleiderer and M. A. Wilde},
doi = {10.1038/s41586-023-06330-y},
issn = {0028-0836},
year = {2023},
date = {2023-08-01},
urldate = {2023-08-01},
journal = {Nature},
volume = {621},
pages = {276},
abstract = {Following nearly a century of research, it remains a puzzle that the low-lying excitations of metals are remarkably well explained by effective single-particle theories of non-interacting bands(1-4). The abundance of interactions in real materials raises the question of direct spectroscopic signatures of phenomena beyond effective single-particle, single-band behaviour. Here we report the identification of quantum oscillations (QOs) in the three-dimensional topological semimetal CoSi, which defy the standard description in two fundamental aspects. First, the oscillation frequency corresponds to the difference of semiclassical quasiparticle (QP) orbits of two bands, which are forbidden as half of the trajectory would oppose the Lorentz force. Second, the oscillations exist up to above 50 K, in strong contrast to all other oscillatory components, which vanish below a few kelvin. Our findings are in excellent agreement with generic model calculations of QOs of the QP lifetime (QPL). Because the only precondition for their existence is a nonlinear coupling of at least two electronic orbits, for example, owing to QP scattering on defects or collective excitations, such QOs of the QPL are generic for any metal featuring Landau quantization with several orbits. They are consistent with certain frequencies in topological semimetals(5-9), unconventional superconductors(10,11), rare-earth compounds(12-14) and Rashba systems(15), and permit to identify and gauge correlation phenomena, for example, in two-dimensional materials(16,17) and multiband metals(18).},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
Following nearly a century of research, it remains a puzzle that the low-lying excitations of metals are remarkably well explained by effective single-particle theories of non-interacting bands(1-4). The abundance of interactions in real materials raises the question of direct spectroscopic signatures of phenomena beyond effective single-particle, single-band behaviour. Here we report the identification of quantum oscillations (QOs) in the three-dimensional topological semimetal CoSi, which defy the standard description in two fundamental aspects. First, the oscillation frequency corresponds to the difference of semiclassical quasiparticle (QP) orbits of two bands, which are forbidden as half of the trajectory would oppose the Lorentz force. Second, the oscillations exist up to above 50 K, in strong contrast to all other oscillatory components, which vanish below a few kelvin. Our findings are in excellent agreement with generic model calculations of QOs of the QP lifetime (QPL). Because the only precondition for their existence is a nonlinear coupling of at least two electronic orbits, for example, owing to QP scattering on defects or collective excitations, such QOs of the QPL are generic for any metal featuring Landau quantization with several orbits. They are consistent with certain frequencies in topological semimetals(5-9), unconventional superconductors(10,11), rare-earth compounds(12-14) and Rashba systems(15), and permit to identify and gauge correlation phenomena, for example, in two-dimensional materials(16,17) and multiband metals(18). | |
Prodan, L.; Evans, D. M.; Griffin, S. M.; Oestlin, A.; Altthaler, M.; Lysne, E.; Filippova, I. G.; Shova, S.; Chioncel, L.; Tsurkan, V.; Kézsmárki, I. Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe3Sn Journal Article Appl. Phys. Lett. 123, 021901 (2023). @article{prodan_large_2023,
title = {Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe_{3}Sn},
author = {L. Prodan and D. M. Evans and S. M. Griffin and A. Oestlin and M. Altthaler and E. Lysne and I. G. Filippova and S. Shova and L. Chioncel and V. Tsurkan and I. Kézsmárki},
doi = {10.1063/5.0155295},
issn = {0003-6951},
year = {2023},
date = {2023-07-01},
urldate = {2023-07-01},
journal = {Appl. Phys. Lett.},
volume = {123},
number = {2},
pages = {021901},
abstract = {We report the magnetic anisotropy of kagome bilayer ferromagnet Fe3Sn probed by the bulk magnetometry and magnetic force microscopy (MFM) on high-quality single crystals. The dependence of magnetization on the orientation of the external magnetic field reveals strong easyplane magnetocrystalline anisotropy and anisotropy of the saturation magnetization. The leading magnetocrystalline anisotropy constant shows a monotonous increase from K-1 approximate to -1.0 x 10(6) J/m(3) at 300K to -1.3 x 10(6) J/m(3) at 2K. Our ab initio electronic structure calculations yield the value of total magnetic moment of 7.1 mu(B)=f.u. and a magnetocrystalline anisotropy energy density of -0.57meV=f.u. (-1.62 x 10(6)J/m(3)) both being in reasonable agreement with the experimental values. The MFM imaging reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at the saturation field of similar to 3T applied perpendicular to the kagome plane. The observed vortex-domain structure is well reproduced by the micromagnetic simulations, using the experimentally determined value of the anisotropy and exchange stiffness. (c) 2023 Author(s).},
keywords = {A4, A5},
pubstate = {published},
tppubtype = {article}
}
We report the magnetic anisotropy of kagome bilayer ferromagnet Fe3Sn probed by the bulk magnetometry and magnetic force microscopy (MFM) on high-quality single crystals. The dependence of magnetization on the orientation of the external magnetic field reveals strong easyplane magnetocrystalline anisotropy and anisotropy of the saturation magnetization. The leading magnetocrystalline anisotropy constant shows a monotonous increase from K-1 approximate to -1.0 x 10(6) J/m(3) at 300K to -1.3 x 10(6) J/m(3) at 2K. Our ab initio electronic structure calculations yield the value of total magnetic moment of 7.1 mu(B)=f.u. and a magnetocrystalline anisotropy energy density of -0.57meV=f.u. (-1.62 x 10(6)J/m(3)) both being in reasonable agreement with the experimental values. The MFM imaging reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at the saturation field of similar to 3T applied perpendicular to the kagome plane. The observed vortex-domain structure is well reproduced by the micromagnetic simulations, using the experimentally determined value of the anisotropy and exchange stiffness. (c) 2023 Author(s). | |
Deyerling, A.; Wilde, M. A.; Pfleiderer, C. Electronic structure of CeAuAl3 using density functional theory Journal Article SciPost Phys. Proc. 11, 008 (2023). @article{deyerling_electronic_2023,
title = {Electronic structure of CeAuAl_{3} using density functional theory},
author = {A. Deyerling and M. A. Wilde and C. Pfleiderer},
doi = {10.21468/SciPostPhysProc.11.008},
year = {2023},
date = {2023-06-05},
urldate = {2023-06-05},
journal = {SciPost Phys. Proc.},
volume = {11},
pages = {008},
abstract = {We studied the magnetic properties and electronic structure of CeAuAl3 using density functional theory. This compound shows a large Sommerfeld coefficient, a Kondo temperature, TK=4K and antiferromagnetic order below TN=1.1K. We calculated the magnetic groundstate of CeAuAl3 and the magnetic anisotropy energies. Treating the 4f-electrons as localized with DFT+U we obtain a good match with the magnetic properties observed experimentally. We also report salient features of the electronic structure of CeAuAl3, including features of the Fermi surface and associated quantum oscillatory spectra, when the 4f-electrons are treated either as localized or itinerant.},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
We studied the magnetic properties and electronic structure of CeAuAl3 using density functional theory. This compound shows a large Sommerfeld coefficient, a Kondo temperature, TK=4K and antiferromagnetic order below TN=1.1K. We calculated the magnetic groundstate of CeAuAl3 and the magnetic anisotropy energies. Treating the 4f-electrons as localized with DFT+U we obtain a good match with the magnetic properties observed experimentally. We also report salient features of the electronic structure of CeAuAl3, including features of the Fermi surface and associated quantum oscillatory spectra, when the 4f-electrons are treated either as localized or itinerant. | |
Kumar, V.; Bauer, A.; Franz, C.; Spallek, J.; Schönmann, R.; Stekiel, M.; Schneidewind, A.; Wilde, M. A.; Pfleiderer, C. Low-temperature antiferromagnetic order in orthorhombic CePdAl3 Journal Article Phys. Rev. Research 5, 023157 (2023). @article{kumar_low-temperature_2023,
title = {Low-temperature antiferromagnetic order in orthorhombic CePdAl_{3}},
author = {V. Kumar and A. Bauer and C. Franz and J. Spallek and R. Schönmann and M. Stekiel and A. Schneidewind and M. A. Wilde and C. Pfleiderer},
doi = {10.1103/PhysRevResearch.5.023157},
year = {2023},
date = {2023-06-01},
urldate = {2023-06-01},
journal = {Phys. Rev. Research},
volume = {5},
number = {2},
pages = {023157},
abstract = {We report the magnetization, ac susceptibility, and specific heat of optically float-zoned single crystals of CePdAl3. In comparison to the properties of polycrystalline CePdAl3 reported in the literature, which displays a tetragonal crystal structure and no long-range magnetic order, our single crystals exhibit an orthorhombic structure (𝐶𝑚𝑐𝑚) and antiferromagnetic order below a Néel temperature 𝑇1=5.6 K. The specific heat at zero field shows two anomalies, namely, a broad transition at 𝑇1=5.6 K followed by a 𝜆-anomaly at 𝑇2=5.4 K. A conservative estimate of the Sommerfeld coefficient of the electronic specific heat, 𝛾=121mJK−2mol−1, indicates a moderately enhanced heavy-fermion ground state. A twin microstructure evolves in the family of planes spanned by the basal plane lattice vectors 𝐚o and 𝐜o , with the magnetic hard axis 𝐛o common to all twins. The antiferromagnetic state is characterized by a strong ao, co easy-plane magnetic anisotropy where the ao direction is the easy axis in the easy plane. A spin-flop transition induced under magnetic field along the easy directions, results in complex magnetic phase diagrams. Taken together, our results reveal a high sensitivity of the magnetic and electronic properties of CePdAl3 to its structural modifications.},
keywords = {A6},
pubstate = {published},
tppubtype = {article}
}
We report the magnetization, ac susceptibility, and specific heat of optically float-zoned single crystals of CePdAl3. In comparison to the properties of polycrystalline CePdAl3 reported in the literature, which displays a tetragonal crystal structure and no long-range magnetic order, our single crystals exhibit an orthorhombic structure (𝐶𝑚𝑐𝑚) and antiferromagnetic order below a Néel temperature 𝑇1=5.6 K. The specific heat at zero field shows two anomalies, namely, a broad transition at 𝑇1=5.6 K followed by a 𝜆-anomaly at 𝑇2=5.4 K. A conservative estimate of the Sommerfeld coefficient of the electronic specific heat, 𝛾=121mJK−2mol−1, indicates a moderately enhanced heavy-fermion ground state. A twin microstructure evolves in the family of planes spanned by the basal plane lattice vectors 𝐚o and 𝐜o , with the magnetic hard axis 𝐛o common to all twins. The antiferromagnetic state is characterized by a strong ao, co easy-plane magnetic anisotropy where the ao direction is the easy axis in the easy plane. A spin-flop transition induced under magnetic field along the easy directions, results in complex magnetic phase diagrams. Taken together, our results reveal a high sensitivity of the magnetic and electronic properties of CePdAl3 to its structural modifications. | |
Schilberth, F.; Jiang, M. -C.; Minami, S.; Kassem, M. A.; Mayr, F.; Koretsune, T.; Tabata, Y.; Waki, T.; Nakamura, H.; Guo, G. -Y.; Arita, R.; Kézsmárki, I.; Bordacs, S. Nodal-line resonance generating the giant anomalous Hall effect of Co3Sn2S2 Journal Article Phys. Rev. B 107, 214441 (2023). @article{schilberth_nodal-line_2023,
title = {Nodal-line resonance generating the giant anomalous Hall effect of Co_{3}Sn_{2}S_{2}},
author = {F. Schilberth and M. -C. Jiang and S. Minami and M. A. Kassem and F. Mayr and T. Koretsune and Y. Tabata and T. Waki and H. Nakamura and G. -Y. Guo and R. Arita and I. Kézsmárki and S. Bordacs},
doi = {10.1103/PhysRevB.107.214441},
issn = {2469-9950},
year = {2023},
date = {2023-06-01},
urldate = {2023-06-01},
journal = {Phys. Rev. B},
volume = {107},
number = {21},
pages = {214441},
abstract = {Giant anomalous Hall effect (AHE) and magneto-optical activity can emerge in magnets with topologically nontrivial degeneracies. However, identifying the specific band-structure features such as Weyl points, nodal lines, or planes which generate the anomalous response is a challenging issue. Since the low-energy interband transitions can govern the static AHE, we addressed this question in the prototypical magnetic Weyl semimetal Co3Sn2S2 also hosting nodal lines by broadband polarized reflectivity and magneto-optical Kerr effect spectroscopy with a focus on the far-infrared range. In the linear dichroism spectrum we observe a strong resonance at 40 meV, which also appears in the optical Hall conductivity and primarily determines the static AHE, and thus confirms its intrinsic origin. Our material-specific theory reproduces the experimental data remarkably well and shows that strongly tilted nodal-line segments around the Fermi energy generate the resonance. While the Weyl points only give vanishing contributions, these segments of the nodal lines gapped by the spin-orbit coupling dominate the low-energy optical response and generate the giant AHE.},
keywords = {A1},
pubstate = {published},
tppubtype = {article}
}
Giant anomalous Hall effect (AHE) and magneto-optical activity can emerge in magnets with topologically nontrivial degeneracies. However, identifying the specific band-structure features such as Weyl points, nodal lines, or planes which generate the anomalous response is a challenging issue. Since the low-energy interband transitions can govern the static AHE, we addressed this question in the prototypical magnetic Weyl semimetal Co3Sn2S2 also hosting nodal lines by broadband polarized reflectivity and magneto-optical Kerr effect spectroscopy with a focus on the far-infrared range. In the linear dichroism spectrum we observe a strong resonance at 40 meV, which also appears in the optical Hall conductivity and primarily determines the static AHE, and thus confirms its intrinsic origin. Our material-specific theory reproduces the experimental data remarkably well and shows that strongly tilted nodal-line segments around the Fermi energy generate the resonance. While the Weyl points only give vanishing contributions, these segments of the nodal lines gapped by the spin-orbit coupling dominate the low-energy optical response and generate the giant AHE. | |
Tóth, B.; Amelin, K.; Rõõm, T.; Nagel, U.; Bauernfeind, A.; Tsurkan, V.; Prodan, L.; von Nidda, H. -A. Krug; Scheffler, M.; Kézsmárki, I.; others, Broadband magnetic resonance spectroscopy in MnSc2S4 Journal Article Sci. Rep. 13, 11069 (2023). @article{toth_broadband_2023,
title = {Broadband magnetic resonance spectroscopy in MnSc_{2}S_{4}},
author = {B. Tóth and K. Amelin and T. Rõõm and U. Nagel and A. Bauernfeind and V. Tsurkan and L. Prodan and H. -A. Krug von Nidda and M. Scheffler and I. Kézsmárki and others},
doi = {10.1038/s41598-023-37911-6},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Sci. Rep.},
volume = {13},
number = {1},
pages = {11069},
abstract = {Recent neutron scattering experiments suggested that frustrated magnetic interactions give rise to antiferromagnetic spiral and fractional skyrmion lattice phases in MnSc2S4. Here, to trace the signatures of these modulated phases, we studied the spin excitations of MnSc2S4 by THz spectroscopy at 300 mK and in magnetic fields up to 12 T and by broadband microwave spectroscopy at various temperatures up to 50 GHz. We found a single magnetic resonance with frequency linearly increasing in field. The small deviation of the Mn2+ ion g-factor from 2},
keywords = {B4},
pubstate = {published},
tppubtype = {article}
}
Recent neutron scattering experiments suggested that frustrated magnetic interactions give rise to antiferromagnetic spiral and fractional skyrmion lattice phases in MnSc2S4. Here, to trace the signatures of these modulated phases, we studied the spin excitations of MnSc2S4 by THz spectroscopy at 300 mK and in magnetic fields up to 12 T and by broadband microwave spectroscopy at various temperatures up to 50 GHz. We found a single magnetic resonance with frequency linearly increasing in field. The small deviation of the Mn2+ ion g-factor from 2 | |
Mohanty, S.; Islam, S. S.; Winterhalter-Stocker, N.; Jesche, A.; Simutis, G.; Wang, Ch.; Guguchia, Z.; Sichelschmidt, J.; Baenitz, M.; Tsirlin, A. A.; Gegenwart, P.; Nath, R. Disordered ground state in the spin-orbit coupled Jeff = 1/2 distorted honeycomb magnet BiYbGeO5 Journal Article Phys. Rev. B 108, 134408 (2023). @article{mohanty_disordered_2023,
title = {Disordered ground state in the spin-orbit coupled J_{eff} = 1/2 distorted honeycomb magnet BiYbGeO_{5}},
author = {S. Mohanty and S. S. Islam and N. Winterhalter-Stocker and A. Jesche and G. Simutis and Ch. Wang and Z. Guguchia and J. Sichelschmidt and M. Baenitz and A. A. Tsirlin and P. Gegenwart and R. Nath},
doi = {10.1103/PhysRevB.108.134408},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Phys. Rev. B},
volume = {108},
number = {13},
pages = {134408},
abstract = {We delineate quantum magnetism in the strongly spin-orbit coupled distorted honeycomb lattice antiferromagnet BiYbGeO5. Our magnetization and heat capacity measurements reveal that its low-temperature behavior is well described by an effective J(eff) = 1/2 Kramers doublet of Yb3+. The ground state is nonmagnetic with a tiny spin gap. Temperature-dependent magnetic susceptibility, magnetization isotherm, and heat capacity can be modeled well assuming isolated spin dimers with anisotropic exchange interactions J(Z) similar or equal to 2.6 K and J(XY) similar or equal to 1.3 K. Heat capacity measurements backed by muon spin relaxation suggest the absence of magnetic long-range order down to at least 80 mK both in zero field and in applied fields. This sets BiYbGeO5 apart from Yb2Si2O7, with its unusual regime of magnon Bose-Einstein condensation, and suggests negligible interdimer couplings, despite only a weak structural deformation of the honeycomb lattice.},
keywords = {B3},
pubstate = {published},
tppubtype = {article}
}
We delineate quantum magnetism in the strongly spin-orbit coupled distorted honeycomb lattice antiferromagnet BiYbGeO5. Our magnetization and heat capacity measurements reveal that its low-temperature behavior is well described by an effective J(eff) = 1/2 Kramers doublet of Yb3+. The ground state is nonmagnetic with a tiny spin gap. Temperature-dependent magnetic susceptibility, magnetization isotherm, and heat capacity can be modeled well assuming isolated spin dimers with anisotropic exchange interactions J(Z) similar or equal to 2.6 K and J(XY) similar or equal to 1.3 K. Heat capacity measurements backed by muon spin relaxation suggest the absence of magnetic long-range order down to at least 80 mK both in zero field and in applied fields. This sets BiYbGeO5 apart from Yb2Si2O7, with its unusual regime of magnon Bose-Einstein condensation, and suggests negligible interdimer couplings, despite only a weak structural deformation of the honeycomb lattice. | |
Bader, V. P.; Ritter, C.; Papke, E.; Gegenwart, P.; Tsirlin, A. A. Geometrical frustration and incommensurate magnetic order in Na3RuO4 with two triangular motifs Journal Article Phys. Rev. B 108, 144424 (2023). @article{bader_geometrical_2023,
title = {Geometrical frustration and incommensurate magnetic order in Na_{3}RuO_{4} with two triangular motifs},
author = {V. P. Bader and C. Ritter and E. Papke and P. Gegenwart and A. A. Tsirlin},
doi = {10.1103/PhysRevB.108.144424},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Phys. Rev. B},
volume = {108},
number = {14},
pages = {144424},
keywords = {B3},
pubstate = {published},
tppubtype = {article}
}
| |
Müller, M.; Weber, J.; Goennenwein, S. T. B.; Kusminskiy, S. V.; Gross, R.; Althammer, M.; Huebl, H. Temperature dependence of the magnon-phonon interaction in high overtone bulk acoustic resonator-ferromagnetic thin film hybrids Journal Article Phy. Rev. Applied 21, 034032 (2023). @article{muller_temperature_2023,
title = {Temperature dependence of the magnon-phonon interaction in high overtone bulk acoustic resonator-ferromagnetic thin film hybrids},
author = {M. Müller and J. Weber and S. T. B. Goennenwein and S. V. Kusminskiy and R. Gross and M. Althammer and H. Huebl},
doi = {10.1103/PhysRevApplied.21.034032},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Phy. Rev. Applied},
volume = {21},
number = {3},
pages = {034032},
keywords = {C3},
pubstate = {published},
tppubtype = {article}
}
| |
Kawano, M.; Pollmann, F.; Knap, M. Unconventional spin transport in strongly correlated kagome systems Journal Article Phys. Rev. B 109, L121111 (2023). @article{kawano_unconventional_2023,
title = {Unconventional spin transport in strongly correlated kagome systems},
author = {M. Kawano and F. Pollmann and M. Knap},
doi = {10.1103/PhysRevB.109.L121111},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Phys. Rev. B},
volume = {109},
number = {12},
pages = {L121111},
keywords = {C5},
pubstate = {published},
tppubtype = {article}
}
| |
Evans, D. M.; Conroy, M.; Puntigam, L.; Croitori, D.; Prodan, L.; Douglas, J. O.; Gault, B.; Tsurkan, V. Direct imaging of spatial heterogeneities in type II superconductors Unpublished (2023), arXiv:2310.20017. @unpublished{evans_direct_2023,
title = {Direct imaging of spatial heterogeneities in type II superconductors},
author = {D. M. Evans and M. Conroy and L. Puntigam and D. Croitori and L. Prodan and J. O. Douglas and B. Gault and V. Tsurkan},
doi = {10.48550/arXiv.2310.20017},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
note = {arXiv:2310.20017},
keywords = {},
pubstate = {published},
tppubtype = {unpublished}
}
| |
