@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

https://doi.org/10.5281/zenodo.21493304},

doi = {10.1103/l5xq-2yrt},

year  = {2026},

date = {2026-09-02},

urldate = {2026-09-02},

journal = {Phys. Rev. Lett.},

volume = {137},

number = {10},

pages = {106503},

abstract = {Ta2⁢NiSe5 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 Ta2⁢Ni⁢(S𝑥⁢Se1−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 Ta2⁢Ni⁢(S𝑥⁢Se1−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 = {A3},

pubstate = {published},

tppubtype = {article}

}

@article{queVisualizingInternalStructure2025,

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.},

note = {datadoi: 10.6084/m9.figshare.27255576},

keywords = {A3},

pubstate = {published},

tppubtype = {article}

}

@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}

}