Song, W.; Liu, G.; Deng, H.; Yang, T.; Li, Y.; Yan, X. -Y.; Liao, R.; Wang, Q.; Xu, J.; Yan, C.; Zhao, Y.; Qin, H.; Wang, D.; Jing, W.; Shen, D.; Nakayama, K.; Sato, T.; Setty, C.; Wu, D.; Song, B.; Ying, T.; Tian, Z.; Sakai, A.; Nakatsuji, S.; Kumar, H.; Kuntscher, C. A.; Wang, Z.; Xue, Q. -K.; Yin, J. -X. Many-body electronic structure in the pyrochlore superconductor CsBi2 and spin-liquid candidate Pr2Ir2O7 Journal Article Phys. Rev. B 112, 245131 (2025). @article{song_many-body_2025,
title = {Many-body electronic structure in the pyrochlore superconductor CsBi_{2} and spin-liquid candidate Pr_{2}Ir_{2}O_{7}},
author = {W. Song and G. Liu and H. Deng and T. Yang and Y. Li and X. -Y. Yan and R. Liao and Q. Wang and J. Xu and C. Yan and Y. Zhao and H. Qin and D. Wang and W. Jing and D. Shen and K. Nakayama and T. Sato and C. Setty and D. Wu and B. Song and T. Ying and Z. Tian and A. Sakai and S. Nakatsuji and H. Kumar and C. A. Kuntscher and Z. Wang and Q. -K. Xue and J. -X. Yin},
url = {https://link.aps.org/doi/10.1103/6jq5-fgxl},
doi = {10.1103/6jq5-fgxl},
year = {2025},
date = {2025-12-12},
urldate = {2025-12-12},
journal = {Phys. Rev. B},
volume = {112},
number = {24},
pages = {245131},
abstract = {The pyrochlore lattice materials can exhibit geometrical frustration, while the related many-body electronic states remain elusive. In this work, we performed scanning tunneling microscopy measurements on the pyrochlore superconductor CsBi2 and spin liquid Pr2Ir2O7 at 0.3 K. For the first time, we obtained atomically resolved images of their (111) surfaces, revealing a hexagonal lattice or a kagome lattice. Tunneling spectroscopy in CsBi2 reveals a nearly fully opened superconductivity gap. The ratio of 2Δ/𝑘_𝐵𝑇_C=4.7 suggests relatively strong coupling superconductivity, as compared with that in kagome superconductors 𝐴V3Sb5 (𝐴 = K, Rb, Cs). In contrast to the previous study categorizing CsBi2 as a type-I superconductor, the applied magnetic field induces a hexagonal vortex lattice in which each vortex core exhibits an intriguing threefold symmetry state. In Pr2Ir2O7, we observed a spatially homogeneous Kondo-lattice resonance, which is compared with that in the kagome Kondo-lattice material CsCr6Sb6. We further discover that the Kondo resonance exhibits a spatial modulation with threefold symmetry, and the applied magnetic field induces a Zeeman splitting of the Kondo resonance with intriguing atomic site dependence. We discuss the relations of these many-body electronic phenomena with the pyrochlore lattice geometry and its charge or spin frustration. Our systematic observations offer atomic-scale insights into the many-body electronic structures of the geometrically frustrated pyrochlore superconductors and spin liquids.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The pyrochlore lattice materials can exhibit geometrical frustration, while the related many-body electronic states remain elusive. In this work, we performed scanning tunneling microscopy measurements on the pyrochlore superconductor CsBi2 and spin liquid Pr2Ir2O7 at 0.3 K. For the first time, we obtained atomically resolved images of their (111) surfaces, revealing a hexagonal lattice or a kagome lattice. Tunneling spectroscopy in CsBi2 reveals a nearly fully opened superconductivity gap. The ratio of 2Δ/𝑘_𝐵𝑇_C=4.7 suggests relatively strong coupling superconductivity, as compared with that in kagome superconductors 𝐴V3Sb5 (𝐴 = K, Rb, Cs). In contrast to the previous study categorizing CsBi2 as a type-I superconductor, the applied magnetic field induces a hexagonal vortex lattice in which each vortex core exhibits an intriguing threefold symmetry state. In Pr2Ir2O7, we observed a spatially homogeneous Kondo-lattice resonance, which is compared with that in the kagome Kondo-lattice material CsCr6Sb6. We further discover that the Kondo resonance exhibits a spatial modulation with threefold symmetry, and the applied magnetic field induces a Zeeman splitting of the Kondo resonance with intriguing atomic site dependence. We discuss the relations of these many-body electronic phenomena with the pyrochlore lattice geometry and its charge or spin frustration. Our systematic observations offer atomic-scale insights into the many-body electronic structures of the geometrically frustrated pyrochlore superconductors and spin liquids. |
Misawa, R.; Kitou, S.; Yamada, R.; Gaggl, T.; Nakano, R.; Shibata, Y.; Okamura, Y.; Kriener, M.; Baral, P. R.; Nakamura, Y.; Ōnuki, Y.; Takahashi, Y.; Arima, T.; Jovanovic, M.; Schoop, L. M.; Hirschberger, M. Successive orthorhombic distortions in kagome metals by molecular orbital formation Journal Article Adv. Mater. e13015 (2025). @article{misawa_successive_2025,
title = {Successive orthorhombic distortions in kagome metals by molecular orbital formation},
author = {R. Misawa and S. Kitou and R. Yamada and T. Gaggl and R. Nakano and Y. Shibata and Y. Okamura and M. Kriener and P. R. Baral and Y. Nakamura and Y. Ōnuki and Y. Takahashi and T. Arima and M. Jovanovic and L. M. Schoop and M. Hirschberger},
url = {https://advanced.onlinelibrary.wiley.com/doi/abs/10.1002/adma.202513015},
doi = {10.1002/adma.202513015},
year = {2025},
date = {2025-12-05},
urldate = {2025-12-01},
journal = {Adv. Mater.},
pages = {e13015},
abstract = {The kagome lattice, with its inherent frustration, hosts a plethora of exotic phenomena, including the emergence of 3q charge-density-wave order. The high rotational symmetry required to realize such an unconventional charge order is broken in many kagome materials by orthorhombic distortions at high temperature, the origin of which remains much less examined despite their ubiquity. In this study, synchrotron X-ray diffraction reveals a structural phase transition from a parent hexagonal structure to an orthorhombic groundstate, mediated by a critical regime with diffuse scattering in the prototypical kagome metals RRu3Si2 (R = Nd, Pr). Structural analysis uncovers partially ordered bonds between kagome layers in the orthorhombic phases. Accordingly, a short-range correlated dimer model on the kagome layers reproduces the diffuse scattering, with the short-range order arising from competing structures induced by the geometrical frustration of the kagome lattice. The observations point to molecular orbital formation between Ru $4d_zˆ2$ orbitals as the driving force behind the transition, consistent with ab initio calculations. A framework based on electronegativity and a tolerance factor is proposed to evaluate the stability of the hexagonal phase in various kagome metals, guiding the design of highly symmetric materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The kagome lattice, with its inherent frustration, hosts a plethora of exotic phenomena, including the emergence of 3q charge-density-wave order. The high rotational symmetry required to realize such an unconventional charge order is broken in many kagome materials by orthorhombic distortions at high temperature, the origin of which remains much less examined despite their ubiquity. In this study, synchrotron X-ray diffraction reveals a structural phase transition from a parent hexagonal structure to an orthorhombic groundstate, mediated by a critical regime with diffuse scattering in the prototypical kagome metals RRu3Si2 (R = Nd, Pr). Structural analysis uncovers partially ordered bonds between kagome layers in the orthorhombic phases. Accordingly, a short-range correlated dimer model on the kagome layers reproduces the diffuse scattering, with the short-range order arising from competing structures induced by the geometrical frustration of the kagome lattice. The observations point to molecular orbital formation between Ru $4d_zˆ2$ orbitals as the driving force behind the transition, consistent with ab initio calculations. A framework based on electronegativity and a tolerance factor is proposed to evaluate the stability of the hexagonal phase in various kagome metals, guiding the design of highly symmetric materials. |
Chmeruk, A.; Jones, D.; Balducci, R.; Ebad-Allah, J.; Beiuşeanu, F.; Schilberth, F.; Kassem, M. A.; Schade, U.; Veber, A.; Puskar, L.; Tabata, Y.; Waki, T.; Nakamura, H.; Kuntscher, C. A.; Östlin, A.; Chioncel, L. Suppression of magnetism in Co3Sn2S2 under external pressure Unpublished (2025), arXiv:2511.08141. @unpublished{chmeruk_suppression_2025,
title = {Suppression of magnetism in Co_{3}Sn_{2}S_{2} under external pressure},
author = {A. Chmeruk and D. Jones and R. Balducci and J. Ebad-Allah and F. Beiuşeanu and F. Schilberth and M. A. Kassem and U. Schade and A. Veber and L. Puskar and Y. Tabata and T. Waki and H. Nakamura and C. A. Kuntscher and A. Östlin and L. Chioncel},
url = {https://arxiv.org/abs/2511.08141},
doi = {10.48550/arXiv.2511.08141},
year = {2025},
date = {2025-11-11},
urldate = {2025-11-11},
abstract = {The ability to control the magnetic state provides a powerful means to tune the underlying band topology, enabling transitions between distinct electronic phases and the emergence of novel quantum phenomena. In this work, we address the evolution of ferromagnetic state upon applying external pressures up to 10.8~GPa using a combined experimental and theoretical study. The standard emph{ab initio} Density Functional Theory computation including ionic relaxations grossly overestimates the unit cell magnetization as a function of pressure. In our theoretical analysis we identify two possible mechanisms to remedy this shortcoming. Matching the experimental observations is achieved by a symmetry-preserving adjustment of the sulfur atoms position within the unit cell. Alternatively, we explore various combinations of the exchange and correlation parts of the effective potential which reproduce the experimental magnetization, the structural parameters and the measured optical conductivity spectra. Thus, the pressure-dependent behavior of magnetization demands a careful theoretical treatment and analysis of theoretical and experimental data. },
note = {arXiv:2511.08141},
keywords = {},
pubstate = {published},
tppubtype = {unpublished}
}
The ability to control the magnetic state provides a powerful means to tune the underlying band topology, enabling transitions between distinct electronic phases and the emergence of novel quantum phenomena. In this work, we address the evolution of ferromagnetic state upon applying external pressures up to 10.8~GPa using a combined experimental and theoretical study. The standard emph{ab initio} Density Functional Theory computation including ionic relaxations grossly overestimates the unit cell magnetization as a function of pressure. In our theoretical analysis we identify two possible mechanisms to remedy this shortcoming. Matching the experimental observations is achieved by a symmetry-preserving adjustment of the sulfur atoms position within the unit cell. Alternatively, we explore various combinations of the exchange and correlation parts of the effective potential which reproduce the experimental magnetization, the structural parameters and the measured optical conductivity spectra. Thus, the pressure-dependent behavior of magnetization demands a careful theoretical treatment and analysis of theoretical and experimental data. |
Wu, Y.; Dai, Z.; Anand, S.; Lin, S. -H.; Yang, Q.; Wang, L.; Pollmann, F.; Zaletel, M. P. Alternating and Gaussian Fermionic Isometric Tensor Network States Journal Article PRX Quantum 6, 040324 (2025). @article{wu_alternating_2025,
title = {Alternating and Gaussian Fermionic Isometric Tensor Network States},
author = {Y. Wu and Z. Dai and S. Anand and S. -H. Lin and Q. Yang and L. Wang and F. Pollmann and M. P. Zaletel},
url = {https://link.aps.org/doi/10.1103/8ypw-c8t4},
doi = {10.1103/8ypw-c8t4},
year = {2025},
date = {2025-11-05},
urldate = {2025-11-01},
journal = {PRX Quantum},
volume = {6},
number = {4},
pages = {040324},
abstract = {Isometric tensor networks in two dimensions enable efficient and accurate study of quantum many-body states, yet the effect of the isometric restriction on the represented quantum states is not fully understood. We address this question in two main contributions. First, we introduce an improved variant of isometric tensor network states (isoTNS) in two dimensions, where the isometric arrows on the columns of the network alternate between pointing upward and downward; hence the name alternating isometric tensor network states. Second, we introduce a numerical tool—the isometric Gaussian fermionic TNS (isoGfTNS)—that incorporates isometric constraints into the framework of Gaussian fermionic tensor network states. We demonstrate in numerous ways that alternating isoTNSs represent many-body ground states of two-dimensional quantum systems significantly better than the original isoTNSs. First, we show that the entanglement in an isoTNS is mediated along the isometric arrows and that alternating isoTNSs mediate entanglement more efficiently than conventional isoTNSs. Second, alternating isoTNSs correspond to a deeper, and thus more representative, sequential-circuit construction of depth 𝒪(𝐿𝑥 ⋅𝐿𝑦) compared to the original isoTNSs of depth 𝒪(𝐿𝑥 +𝐿𝑦). Third, using the Gaussian framework and gradient-based energy minimization, we provide numerical evidence of better bond-dimension scaling and variational energy of alternating isoGfTNSs for ground states of various free-fermionic models, including the Fermi surface, the band insulator, and the 𝑝𝑥 +𝑖𝑝𝑦 mean-field superconductor. Finally, benchmarking on the transverse-field Ising model, we demonstrate that an alternating isoTNS provides substantially improved performance and stability relative to the original isoTNS for the ground-state search algorithm in interacting systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Isometric tensor networks in two dimensions enable efficient and accurate study of quantum many-body states, yet the effect of the isometric restriction on the represented quantum states is not fully understood. We address this question in two main contributions. First, we introduce an improved variant of isometric tensor network states (isoTNS) in two dimensions, where the isometric arrows on the columns of the network alternate between pointing upward and downward; hence the name alternating isometric tensor network states. Second, we introduce a numerical tool—the isometric Gaussian fermionic TNS (isoGfTNS)—that incorporates isometric constraints into the framework of Gaussian fermionic tensor network states. We demonstrate in numerous ways that alternating isoTNSs represent many-body ground states of two-dimensional quantum systems significantly better than the original isoTNSs. First, we show that the entanglement in an isoTNS is mediated along the isometric arrows and that alternating isoTNSs mediate entanglement more efficiently than conventional isoTNSs. Second, alternating isoTNSs correspond to a deeper, and thus more representative, sequential-circuit construction of depth 𝒪(𝐿𝑥 ⋅𝐿𝑦) compared to the original isoTNSs of depth 𝒪(𝐿𝑥 +𝐿𝑦). Third, using the Gaussian framework and gradient-based energy minimization, we provide numerical evidence of better bond-dimension scaling and variational energy of alternating isoGfTNSs for ground states of various free-fermionic models, including the Fermi surface, the band insulator, and the 𝑝𝑥 +𝑖𝑝𝑦 mean-field superconductor. Finally, benchmarking on the transverse-field Ising model, we demonstrate that an alternating isoTNS provides substantially improved performance and stability relative to the original isoTNS for the ground-state search algorithm in interacting systems. |
Yamada, R.; Birch, M. T.; Baral, P. R.; Okumura, S.; Nakano, R.; Gao, S.; Ezawa, M.; Nomoto, T.; Masell, J.; Ishihara, Y.; Kolincio, K. K.; Belopolski, I.; Sagayama, H.; Nakao, H.; Ohishi, K.; Ohhara, T.; Kiyanagi, R.; Nakajima, T.; Tokura, Y.; Arima, T.; Motome, Y.; Hirschmann, M. M.; Hirschberger, M. A metallic p-wave magnet with commensurate spin helix Journal Article Nature 646, 837 (2025). @article{yamada_metallic_2025,
title = {A metallic p-wave magnet with commensurate spin helix},
author = {R. Yamada and M. T. Birch and P. R. Baral and S. Okumura and R. Nakano and S. Gao and M. Ezawa and T. Nomoto and J. Masell and Y. Ishihara and K. K. Kolincio and I. Belopolski and H. Sagayama and H. Nakao and K. Ohishi and T. Ohhara and R. Kiyanagi and T. Nakajima and Y. Tokura and T. Arima and Y. Motome and M. M. Hirschmann and M. Hirschberger},
url = {https://doi.org/10.1038/s41586-025-09633-4},
doi = {10.1038/s41586-025-09633-4},
year = {2025},
date = {2025-10-22},
urldate = {2025-10-01},
journal = {Nature},
volume = {646},
number = {8086},
pages = {837},
abstract = {Antiferromagnetic states with a spin-split electronic structure give rise to spintronic, magnonic and electronic phenomena despite (near-)zero net magnetization [1–7]. The simplest odd-parity spin splitting—p wave—was originally proposed to emerge from a collective instability in interacting electron systems [8–12]. Recent theory has identified a distinct route to realize p-wave spin-split electronic bands without strong correlations [13,14], termed p-wave magnetism. Here we demonstrate an experimental realization of a metallic p-wave magnet. The odd-parity spin splitting of delocalized conduction electrons arises from their coupling to an antiferromagnetic texture of localized magnetic moments: a coplanar spin helix whose magnetic period is an even multiple of the chemical unit cell, as revealed by X-ray scattering experiments. This texture breaks space-inversion symmetry but approximately preserves time-reversal symmetry up to a half-unit-cell translation—thereby fulfilling the symmetry conditions for p-wave magnetism. Consistent with theoretical predictions, our p-wave magnet shows a characteristic anisotropy in the electronic conductivity [13–15]. Relativistic spin–orbit coupling and a tiny spontaneous net magnetization further break time-reversal symmetry, resulting in a giant anomalous Hall effect (Hall conductivity >600 S cm−1, Hall angle >3%), for an antiferromagnet. Our model calculations show that the spin-nodal planes found in the electronic structure of p-wave magnets are readily gapped by a small perturbation to induce the anomalous Hall effect. We establish metallic p-wave magnets as an ideal platform to explore the functionality of spin-split electronic states in magnets, superconductors, and in spintronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Antiferromagnetic states with a spin-split electronic structure give rise to spintronic, magnonic and electronic phenomena despite (near-)zero net magnetization [1–7]. The simplest odd-parity spin splitting—p wave—was originally proposed to emerge from a collective instability in interacting electron systems [8–12]. Recent theory has identified a distinct route to realize p-wave spin-split electronic bands without strong correlations [13,14], termed p-wave magnetism. Here we demonstrate an experimental realization of a metallic p-wave magnet. The odd-parity spin splitting of delocalized conduction electrons arises from their coupling to an antiferromagnetic texture of localized magnetic moments: a coplanar spin helix whose magnetic period is an even multiple of the chemical unit cell, as revealed by X-ray scattering experiments. This texture breaks space-inversion symmetry but approximately preserves time-reversal symmetry up to a half-unit-cell translation—thereby fulfilling the symmetry conditions for p-wave magnetism. Consistent with theoretical predictions, our p-wave magnet shows a characteristic anisotropy in the electronic conductivity [13–15]. Relativistic spin–orbit coupling and a tiny spontaneous net magnetization further break time-reversal symmetry, resulting in a giant anomalous Hall effect (Hall conductivity >600 S cm−1, Hall angle >3%), for an antiferromagnet. Our model calculations show that the spin-nodal planes found in the electronic structure of p-wave magnets are readily gapped by a small perturbation to induce the anomalous Hall effect. We establish metallic p-wave magnets as an ideal platform to explore the functionality of spin-split electronic states in magnets, superconductors, and in spintronic devices. |
