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TT: Fachverband Tiefe Temperaturen
TT 49: Correlated Electrons: Charge Order
TT 49.3: Vortrag
Mittwoch, 11. März 2026, 11:15–11:30, HSZ/0101
Electronic band gap tuning of interchain phonon transport in Ta2Ni(SxSe1−x)5 — Yuan-Shan Zhang1, Masahiko Isobe1, Hidenori Takagi1,2,3, and •Dennis Huang1 — 1Max Planck Institute for Solid State Research, Stuttgart, Germany — 2Institute for Functional Matter and Quantum Technologies, University of Stuttgart, Germany — 3National Institute for Materials Science, Tsukuba, Japan
The dual electronic and structural characters of the 326 K transition in the quasi-one-dimensional compound Ta2NiSe5 continues to inspire heated discussion as to the origin of its primary driving force. The current state of affairs may be best summarized as a three-party debate, in which electron-hole interactions (excitonic insulator), electron-lattice coupling (hybridization gap), and “instrinsic” lattice effects are all championed to play some role. The isostructural compound Ta2NiS5 should serve as a valuable foil for better understanding Ta2NiSe5, as substitution of Se for S enlarges the single-particle electronic band gap, which diminishes the role of electronic degrees of freedom and greatly reduces the transition temperature. Here, we report thermal transport measurements that probe the interchain phonon conductivity of Ta2Ni(SxSe1−x)5. A soft-phonon anomaly observed in the Se-rich compounds is absent in the S-rich compounds, implying the crucial role of electronic (excitonic and hybridization-gap) fluctuations that couple to the lattice and boost the structural transition temperature.
Keywords: Excitonic insulator; Thermal transport; Electron-phonon coupling; Quasi-one-dimensionality; Lattice fluctuations