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Tsurkan, V.; Kézsmárki, I.; Takagi, H.; Huang, D. Tunable flat band on the surface of a rhombohedral kagome ferromagnet Unpublished (2026), arXiv.2609.19857. @unpublished{que2026tunableflatbandsurface,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tppubtype = {unpublished}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 = {2026-09-07},
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. |
Zhang, Y. -S.; Isobe, M.; Takagi, H.; Huang, D. Electronic tuning of the soft-phonon transport anomaly in Ta2Ni(SxSe1-x)5 Journal Article Phys. Rev. Lett. 137, 106503 (2026), datadoi: 10.5281/zenodo.21493304. @article{l5xq-2yrt,
title = {Electronic tuning of the soft-phonon transport anomaly in Ta_{2}Ni(S_{x}Se_{1-x})_{5}},
author = {Y. -S. Zhang and M. Isobe and H. Takagi and D. Huang},
url = {https://link.aps.org/doi/10.1103/l5xq-2yrt},
doi = {10.1103/l5xq-2yrt},
year = {2026},
date = {2026-09-02},
urldate = {2026-09-01},
journal = {Phys. Rev. Lett.},
volume = {137},
number = {10},
pages = {106503},
abstract = {Ta2NiSe5 continues to be investigated for its phase transition at 𝑇c=326 K, where it develops both an electronic gap and a distortion of its Ta/Ni chains. One intriguing feature at 𝑇c seen in thermal transport is the giant anisotropic scattering of phonons moving perpendicular to the chains, which is apparently associated with the softening of a transverse acoustic phonon, but whose microscopic origin and significance demand clarification. By tuning the normal-state band overlap or gap with S substitution, we uncover a close connection between this soft-phonon transport anomaly and underlying electronic instabilities: when Ta2Ni(S𝑥Se1−𝑥)5 approaches a band insulator at high 𝑥, and signatures of the electronic transition are suppressed, the soft-phonon transport anomaly concomitantly vanishes. Our results establish the following picture for the Ta2Ni(S𝑥Se1−𝑥)5 family: near the S end, a sole lattice instability gives rise to a weak structural transition with 𝑇c approaching 130 K. Near the Se end, additional electronic instabilities boost 𝑇c up to 326 K and amplify experimental signatures of the transition. The strong interaction between electrons, holes, and the lattice is manifested as a soft-phonon transport anomaly accompanied by electronic fluctuations, which include excitonic and hybridization-gap fluctuations.},
note = {datadoi: 10.5281/zenodo.21493304},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Ta2NiSe5 continues to be investigated for its phase transition at 𝑇c=326 K, where it develops both an electronic gap and a distortion of its Ta/Ni chains. One intriguing feature at 𝑇c seen in thermal transport is the giant anisotropic scattering of phonons moving perpendicular to the chains, which is apparently associated with the softening of a transverse acoustic phonon, but whose microscopic origin and significance demand clarification. By tuning the normal-state band overlap or gap with S substitution, we uncover a close connection between this soft-phonon transport anomaly and underlying electronic instabilities: when Ta2Ni(S𝑥Se1−𝑥)5 approaches a band insulator at high 𝑥, and signatures of the electronic transition are suppressed, the soft-phonon transport anomaly concomitantly vanishes. Our results establish the following picture for the Ta2Ni(S𝑥Se1−𝑥)5 family: near the S end, a sole lattice instability gives rise to a weak structural transition with 𝑇c approaching 130 K. Near the Se end, additional electronic instabilities boost 𝑇c up to 326 K and amplify experimental signatures of the transition. The strong interaction between electrons, holes, and the lattice is manifested as a soft-phonon transport anomaly accompanied by electronic fluctuations, which include excitonic and hybridization-gap fluctuations. |
Schilberth, F.; Vasin, K.; Knauft, M.; Kondákor, M.; Vuckovic, M.; Herrmann, N.; Penc, K.; Minola, M.; Keimer, B.; Martinez, V. A.; Panda, K.; Sirenko, A. A.; Prodan, L.; Tsurkan, V.; Tsirlin, A. A.; Kézsmárki, I.; Deisenhofer, J. Magnetic circular dichroism of THz modes and selection rules of Raman-active optical phonons in the polar altermagnet candidate Mn2Mo3O8 Unpublished (2026), arXiv:2608.01062. @unpublished{schilberth_magnetic_2026,
title = {Magnetic circular dichroism of THz modes and selection rules of Raman-active optical phonons in the polar altermagnet candidate Mn_{2}Mo_{3}O_{8}},
author = {F. Schilberth and K. Vasin and M. Knauft and M. Kondákor and M. Vuckovic and N. Herrmann and K. Penc and M. Minola and B. Keimer and V. A. Martinez and K. Panda and A. A. Sirenko and L. Prodan and V. Tsurkan and A. A. Tsirlin and I. Kézsmárki and J. Deisenhofer},
url = {https://arxiv.org/abs/2608.01062},
doi = {10.48550/arXiv.2608.01062},
year = {2026},
date = {2026-08-02},
urldate = {2026-08-01},
note = {arXiv:2608.01062},
keywords = {},
pubstate = {published},
tppubtype = {unpublished}
}
|
