Electronic tuning of the soft-phonon transport anomaly in Ta2Ni(SxSe1−x)5
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/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.
Versions
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BibTeX
@misc{zhang2026electronic,
title = {{Electronic tuning of the soft-phonon transport anomaly in Ta$_2$Ni(S$_x$Se$_1-x$)$_5$}},
author = {Yuan-Shan Zhang and Masahiko Isobe and Hidenori Takagi and Dennis Huang},
howpublished = {arXiv},
year = {2026},
month = jul,
doi = {10.48550/arxiv.2607.11679},
eprint = {2607.11679},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.11679},
}
RIS
TY - UNPB
TI - Electronic tuning of the soft-phonon transport anomaly in Ta_2Ni(S_xSe_1−x)_5
AU - Yuan-Shan Zhang
AU - Masahiko Isobe
AU - Hidenori Takagi
AU - Dennis Huang
PY - 2026
DA - 2026/07/13
PB - arXiv
DO - 10.48550/arxiv.2607.11679
UR - https://arxiv.org/abs/2607.11679
AB - Ta_2NiSe_5 continues to be investigated for its phase transition at T_c = 326 K, where it develops both an electronic gap and a distortion of its Ta/Ni chains. One intriguing feature at T_c 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/gap with S substitution, we uncover a close connection between this soft-phonon transport anomaly and underlying electronic instabilities: When Ta_2Ni(S_xSe_1−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 Ta_2Ni(S_xSe_1−x)_5 family: Near the S end, a sole lattice instability gives rise to a weak structural transition with T_c approaching 130 K. Near the Se end, additional electronic instabilities boost T_c 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.
ER -