Relativistic and Anharmonic Contributions to Low Thermal Conductivity in Topological Material BiTe
Peng Wu, Ying Zhang, Lidong Zhang, Jie Sun, Zhikang Cui, Weijian Wang, Zhengtai Liu, Ranran Zhang, Zhanfeng Liu, Tongrui LiAbstract
Understanding heat transport in topological materials containing heavy elements remains a challenge because relativistic effects and higher-order lattice anharmonicity may both be relevant to thermal transport. Here, BiTe is investigated as a representative system in which the effects of spin–orbit coupling (SOC) and higher-order phonon anharmonicity are examined separately. Angle-resolved photoemission spectroscopy and density functional theory confirm that SOC is essential to the topological electronic structure, while machine-learning moment-tensor potentials enable a quantitative assessment of its influence on phonon transport. Including SOC slightly increases the lattice thermal conductivity by weakening low-frequency phonon scattering. Temperature-dependent Raman spectroscopy reveals mode-dependent higher-order anharmonicity, and explicit transport calculations show that four-phonon scattering substantially suppresses thermal conductivity. These findings demonstrate that both SOC and higher-order phonon scattering should be considered for a reliable description of heat transport in BiTe and provide broader insight into thermal transport in topological materials containing heavy elements.