Gimpel, T.; Büttgen, N.; Prodan, L.; Tsurkan, V.; Tsirlin, A. A.; Nakamura, H.; Kézsmárki, I. Magnetic symmetry and hyperfine fields of V4 tetrahedral clusters in the multiferroic lacunar spinel GeV4S8 Journal Article Phys. Rev. B 114, 154418 (2026). @article{xn3r-b7g6,
title = {Magnetic symmetry and hyperfine fields of V_{4} tetrahedral clusters in the multiferroic lacunar spinel GeV_{4}S_{8}},
author = {T. Gimpel and N. Büttgen and L. Prodan and V. Tsurkan and A. A. Tsirlin and H. Nakamura and I. Kézsmárki},
url = {https://link.aps.org/doi/10.1103/xn3r-b7g6},
doi = {10.1103/xn3r-b7g6},
year = {2026},
date = {2026-09-18},
urldate = {2026-09-18},
journal = {Phys. Rev. B},
volume = {114},
number = {15},
pages = {154418},
abstract = {We use 51V nuclear magnetic resonance (NMR) spectroscopy to investigate the magnetic ground state of the lacunar spinel GeV4S8, which undergoes a structural distortion at 𝑇JT≈30K followed by an antiferromagnetic (AFM) ordering at 𝑇𝑁≈15K. According to our zero- and finite-field NMR data, the four V-sites of V4 clusters become magnetically inequivalent in the AFM state: Two of them share the same internal field, while the other two sites are characterized by different internal fields. The angular dependence of the 51V NMR lines, upon rotation of an external magnetic field about the pseudocubic [110] and [100] axes, reveals that the internal fields are either parallel to the orthorhombic 𝑎 axis at all four V-sites of the V4 tetrahedra, or they form an orthogonal pattern, where two V-sites have internal field along the 𝑎 axis and the other two along the 𝑏 axis. Based on these results, further supported by the observation of distinct spin-echo modulations of the inequivalent V-sites, we conclude that the magnetic space group of the AFM state is 𝑃𝑏𝑚𝑛21 or 𝑃𝑚𝑛′2′1.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We use 51V nuclear magnetic resonance (NMR) spectroscopy to investigate the magnetic ground state of the lacunar spinel GeV4S8, which undergoes a structural distortion at 𝑇JT≈30K followed by an antiferromagnetic (AFM) ordering at 𝑇𝑁≈15K. According to our zero- and finite-field NMR data, the four V-sites of V4 clusters become magnetically inequivalent in the AFM state: Two of them share the same internal field, while the other two sites are characterized by different internal fields. The angular dependence of the 51V NMR lines, upon rotation of an external magnetic field about the pseudocubic [110] and [100] axes, reveals that the internal fields are either parallel to the orthorhombic 𝑎 axis at all four V-sites of the V4 tetrahedra, or they form an orthogonal pattern, where two V-sites have internal field along the 𝑎 axis and the other two along the 𝑏 axis. Based on these results, further supported by the observation of distinct spin-echo modulations of the inequivalent V-sites, we conclude that the magnetic space group of the AFM state is 𝑃𝑏𝑚𝑛21 or 𝑃𝑚𝑛′2′1. |
Que, X.; He, Q.; Zhou, L.; Prodan, L.; Tsurkan, V.; Kézsmárki, I.; Takagi, H.; Huang, D. Tunable flat band on the surface of a rhombohedral kagome ferromagnet Unpublished (2026), arXiv.2609.19857. @unpublished{que2026tunableflatbandsurface,
title = {Tunable flat band on the surface of a rhombohedral kagome ferromagnet},
author = {X. Que and Q. He and L. Zhou and L. Prodan and V. Tsurkan and I. Kézsmárki and H. Takagi and D. Huang},
url = {https://arxiv.org/abs/2609.19857},
doi = {10.48550/arXiv.2609.19857},
year = {2026},
date = {2026-09-17},
urldate = {2026-09-01},
abstract = {A central goal in the exploration of kagome-based materials is the realization of a flat band that has meV bandwidth and lies close to the Fermi energy. The prevailing assumption is that band flattening originates from destructive hopping processes on the kagome lattice. We perform scanning tunneling microscopy (STM) on the layered kagome ferromagnet Fe3Sn2 and show that it indeed hosts a flat band near the Fermi energy, which is manifested as a sharp peak in the differential tunneling conductance. First-principles slab calculations reveal, however, that this band is flattened not by the destructive interference of intralayer hopping, but by interlayer hopping between rhombohedral-stacked kagome planes in Fe3Sn2, and is confined to the surface layer. This surface band, forming in the vicinity of the Brillouin zone corners K¯ and K′¯, exhibits rich magnetic-field dependence, including fine structure due to valley-symmetry breaking by rotated Fe moments, as well as a persistent diamagnetic shift associated with orbital magnetic moments, all reproduced by our calculations. Our results, highlighting the crucial role of layer stacking on the band structure of kagome magnets, demonstrate experimentally an alternative mechanism of generating magnetically tunable flat bands in atomically thin volumes of topological magnets.},
note = {arXiv.2609.19857},
keywords = {},
pubstate = {published},
tppubtype = {unpublished}
}
A central goal in the exploration of kagome-based materials is the realization of a flat band that has meV bandwidth and lies close to the Fermi energy. The prevailing assumption is that band flattening originates from destructive hopping processes on the kagome lattice. We perform scanning tunneling microscopy (STM) on the layered kagome ferromagnet Fe3Sn2 and show that it indeed hosts a flat band near the Fermi energy, which is manifested as a sharp peak in the differential tunneling conductance. First-principles slab calculations reveal, however, that this band is flattened not by the destructive interference of intralayer hopping, but by interlayer hopping between rhombohedral-stacked kagome planes in Fe3Sn2, and is confined to the surface layer. This surface band, forming in the vicinity of the Brillouin zone corners K¯ and K′¯, exhibits rich magnetic-field dependence, including fine structure due to valley-symmetry breaking by rotated Fe moments, as well as a persistent diamagnetic shift associated with orbital magnetic moments, all reproduced by our calculations. Our results, highlighting the crucial role of layer stacking on the band structure of kagome magnets, demonstrate experimentally an alternative mechanism of generating magnetically tunable flat bands in atomically thin volumes of topological magnets. |
Chatterjee, S.; Agarwal, A.; Borkenhagen, R.; Kuntscher, C. A.; Winiarski, M. J.; Pavlosiuk, O.; Wiśniewski, P.; Kaczorowski, D. Anisotropic magnetotransport and optical response of the multiband low-carrier antiferromagnet DyPtSb Journal Article Phys. Rev. B 114, 154412 (2026). @article{chatterjeeAnisotropicMagnetotransportOptical2026,
title = {Anisotropic magnetotransport and optical response of the multiband low-carrier antiferromagnet DyPtSb},
author = {S. Chatterjee and A. Agarwal and R. Borkenhagen and C. A. Kuntscher and M. J. Winiarski and O. Pavlosiuk and P. Wiśniewski and D. Kaczorowski},
url = {https://link.aps.org/doi/10.1103/lqnh-7d73},
doi = {10.1103/lqnh-7d73},
year = {2026},
date = {2026-09-14},
urldate = {2026-09-01},
journal = {Phys. Rev. B},
volume = {114},
number = {15},
pages = {154412},
abstract = {We report a combined study of the magnetic, electrical transport, optical reflectivity, and electronic properties of single-crystalline DyPtSb, a half-Heusler antiferromagnet that orders at 2.2 K. The electrical resistivity exhibits semiconductor-like behavior and the Hall response becomes strongly nonlinear at low temperatures, indicating multiband transport with hole- and electron-type pockets. Angular magnetoresistance measurements revealed occurrence of twofold and fourfold symmetry components, both of which change sign near magnetic field of 4 T at 2 K, suggesting a field-induced modification of the electronic structure near the crossover from the antiferromagnetic to the spin-polarized regime. The optical spectroscopy revealed a temperature-dependent plasma edge and a Drude response, consistent with the bulk electrical transport data. In contrast to the characteristic feature of three-dimensional Dirac and Weyl semimetals, the optical conductivity of DyPtSb does not exhibit clear linear-in-frequency behavior at low energy. The results of ab initio electronic band-structure calculations revealed that the compound is a narrow-gap semiconductor, showing pronounced anisotropy of valence bands and strong sensitivity to magnetic polarization. DyPtSb was characterized as a multiband low-carrier antiferromagnet whose electrical transport properties are closely tied to the evolution of its electronic structure.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report a combined study of the magnetic, electrical transport, optical reflectivity, and electronic properties of single-crystalline DyPtSb, a half-Heusler antiferromagnet that orders at 2.2 K. The electrical resistivity exhibits semiconductor-like behavior and the Hall response becomes strongly nonlinear at low temperatures, indicating multiband transport with hole- and electron-type pockets. Angular magnetoresistance measurements revealed occurrence of twofold and fourfold symmetry components, both of which change sign near magnetic field of 4 T at 2 K, suggesting a field-induced modification of the electronic structure near the crossover from the antiferromagnetic to the spin-polarized regime. The optical spectroscopy revealed a temperature-dependent plasma edge and a Drude response, consistent with the bulk electrical transport data. In contrast to the characteristic feature of three-dimensional Dirac and Weyl semimetals, the optical conductivity of DyPtSb does not exhibit clear linear-in-frequency behavior at low energy. The results of ab initio electronic band-structure calculations revealed that the compound is a narrow-gap semiconductor, showing pronounced anisotropy of valence bands and strong sensitivity to magnetic polarization. DyPtSb was characterized as a multiband low-carrier antiferromagnet whose electrical transport properties are closely tied to the evolution of its electronic structure. |
Jarc, G.; Tartaglia, G.; Gabriele, F.; Forte, F.; Guarino, A.; Montanaro, A.; Rigoni, E. M.; Khatiwada, N.; Lincetto, C.; Bartolini, G.; Mastropasqua, A.; Mathengattil, S. Y.; Malvestuto, M.; Waqee-Ur-Rehman, M.; Fittipaldi, R.; Deisenhofer, J.; Tsirlin, A. A.; Vecchione, A.; Cuoco, M.; Fausti, D. Raman signatures of a non-reciprocal magnetic phase transition in Ca2RuO4 Unpublished (2026), arXiv.2609.07565. @unpublished{jarc2026ramansignaturesnonreciprocalmagnetic,
title = {Raman signatures of a non-reciprocal magnetic phase transition in Ca_{2}RuO_{4}},
author = {G. Jarc and G. Tartaglia and F. Gabriele and F. Forte and A. Guarino and A. Montanaro and E. M. Rigoni and N. Khatiwada and C. Lincetto and G. Bartolini and A. Mastropasqua and S. Y. Mathengattil and M. Malvestuto and M. Waqee-Ur-Rehman and R. Fittipaldi and J. Deisenhofer and A. A. Tsirlin and A. Vecchione and M. Cuoco and D. Fausti},
url = {https://arxiv.org/abs/2609.07565},
doi = {10.48550/arXiv.2609.07565},
year = {2026},
date = {2026-09-07},
urldate = {2026-09-01},
abstract = {The magnetic behavior of Ca2RuO4 represents a unique puzzle due to the interplay of strong electronic correlations, magneto-elastic interactions, and large spin-orbit coupling. At low temperatures, an anomalous Mott insulating state emerges, characterized by a complex antiferromagnetic order with a collective amplitude excitation of the magnetic moment which has been discussed in analogy with the Higgs mode. We report here evidence of a magnetic first-order phase transition driven by an out-of-plane magnetic field along the crystallographic c-axis of Ca2RuO4. Raman measurements in magnetic field reveal the emergence of mode of magnetic origin and a concomitant modification of the coupling between a phonon and the Higgs amplitude mode. Both the Raman features are characterized by a non-reciprocal hysteresis in magnetic field. Surprisingly, the observed phase transition does not affect the Raman scattering from the in-plane magnons, indicating that the dipolar antiferromagnetic order is preserved. This is consistent with the onset of a new quadrupolar field-controlled state, whose fluctuations structure can trigger an hybridization between the lattice and the magnetic Higgs mode resulting in the observed Raman features.},
note = {arXiv.2609.07565},
keywords = {},
pubstate = {published},
tppubtype = {unpublished}
}
The magnetic behavior of Ca2RuO4 represents a unique puzzle due to the interplay of strong electronic correlations, magneto-elastic interactions, and large spin-orbit coupling. At low temperatures, an anomalous Mott insulating state emerges, characterized by a complex antiferromagnetic order with a collective amplitude excitation of the magnetic moment which has been discussed in analogy with the Higgs mode. We report here evidence of a magnetic first-order phase transition driven by an out-of-plane magnetic field along the crystallographic c-axis of Ca2RuO4. Raman measurements in magnetic field reveal the emergence of mode of magnetic origin and a concomitant modification of the coupling between a phonon and the Higgs amplitude mode. Both the Raman features are characterized by a non-reciprocal hysteresis in magnetic field. Surprisingly, the observed phase transition does not affect the Raman scattering from the in-plane magnons, indicating that the dipolar antiferromagnetic order is preserved. This is consistent with the onset of a new quadrupolar field-controlled state, whose fluctuations structure can trigger an hybridization between the lattice and the magnetic Higgs mode resulting in the observed Raman features. |
Wang, Y.; Wu, Z.; Bhupendra, K. C.; Zhang, D.; Wang, L.; Khare, S. V.; Prodan, L.; Tsurkan, V. Pressure-induced electronic delocalization and superconductivity in GaNb4Se8 Journal Article Phys. Rev. B 114, 175107 (2026). @article{8b8c-2wm3,
title = {Pressure-induced electronic delocalization and superconductivity in GaNb_{4}Se_{8}},
author = {Y. Wang and Z. Wu and K. C. Bhupendra and D. Zhang and L. Wang and S. V. Khare and L. Prodan and V. Tsurkan},
url = {https://link.aps.org/doi/10.1103/8b8c-2wm3},
doi = {10.1103/8b8c-2wm3},
year = {2026},
date = {2026-09-04},
urldate = {2026-09-01},
journal = {Phys. Rev. B},
volume = {114},
number = {17},
pages = {175107},
publisher = {American Physical Society},
abstract = {Understanding how electronic transport evolves from localized to itinerant regimes in correlated cluster solids remains an important challenge in condensed-matter physics. Here, we investigate the pressure-dependent transport properties of the lacunar spinel GaNb4Se8, a cluster Mott insulator at ambient conditions. At ambient pressure, the resistivity follows Efros-Shklovskii variable-range hopping, indicating Coulomb gap–controlled carrier localization. A pressure-induced electronic delocalization process begins at low pressures (∼5 GPa), as evidenced by the continuous suppression of room-temperature resistance. Upon further compression, the system undergoes a broad insulator-to-metal-like crossover in low-temperature transport, culminating in a fully metallic-like ground state at ∼17–18 GPa. In contrast, the crystallographic transition from the cubic phase to the monoclinic 𝐶2 phase starts at ∼20 GPa and ends near ∼32 GPa, demonstrating that the pressure-induced electronic evolution is completed before the onset of long-range structural symmetry breaking. At higher pressures, superconductivity (with a superconducting coherence length ξ(0) ≈ 80–90 Å) emerges from a pressure-induced metallic-like regime. These results establish GaNb4Se8 as a platform for studying correlation-driven evolution of electronic transport in cluster-based solids.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Understanding how electronic transport evolves from localized to itinerant regimes in correlated cluster solids remains an important challenge in condensed-matter physics. Here, we investigate the pressure-dependent transport properties of the lacunar spinel GaNb4Se8, a cluster Mott insulator at ambient conditions. At ambient pressure, the resistivity follows Efros-Shklovskii variable-range hopping, indicating Coulomb gap–controlled carrier localization. A pressure-induced electronic delocalization process begins at low pressures (∼5 GPa), as evidenced by the continuous suppression of room-temperature resistance. Upon further compression, the system undergoes a broad insulator-to-metal-like crossover in low-temperature transport, culminating in a fully metallic-like ground state at ∼17–18 GPa. In contrast, the crystallographic transition from the cubic phase to the monoclinic 𝐶2 phase starts at ∼20 GPa and ends near ∼32 GPa, demonstrating that the pressure-induced electronic evolution is completed before the onset of long-range structural symmetry breaking. At higher pressures, superconductivity (with a superconducting coherence length ξ(0) ≈ 80–90 Å) emerges from a pressure-induced metallic-like regime. These results establish GaNb4Se8 as a platform for studying correlation-driven evolution of electronic transport in cluster-based solids. |
