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MM: Fachverband Metall- und Materialphysik
MM 18: Poster Session I
MM 18.35: Poster
Montag, 16. März 2020, 18:15–20:00, P4
Signatures of quasiparticle transport in excitonic insulator candidate: Ta2NiSe5 — •Yuan-Shan Zhang1, Jan Bruin1, Yosuke Matsumoto1, Masahiko Isobe1, and Hidenori Takagi1,2,3 — 1Max Planck Institute for Solid State Research, Stuttgart, Germany — 2Institute for Functional Matter and Quantum Technologies, University of Stuttgart, Stuttgart, Germany — 3Department of Physics, Univerisity of Tokyo, Japan
Ta2NiSe5 is a narrow gap semiconductor which is electronically quasi-one-dimensional and undergoes a transition to an excitonic insulator at Tc=328K[1], where the electron-hole pairs condense into a many body ground state. Thermal conductivity is a useful probe for the quasi-particle states as well as the relevant phonons in excitonic insulators.
Here, we present the temperature dependence of thermal conductivity κ(T) of single crystals of Ta2NiSe5 around the transition temperature, measured along both parallel and perpendicular to the quasi-one dimensional chain direction. We observed a clear anomaly in κ(T) at Tc: a kink followed by a raid decrease below Tc for the chain direction and a pronounced dip for the perpendicular to the chain direction.
We argue that, while the former originates predominantly from the quasi-particle contribution, the latter represents the phonon contributions scattered by the shear-mode soft phonons coupled strongly to the excitonic state.
[1] Y. F. Lu et al. Nat. Commun., 8 14408(2017)