Anomalous thermal expansion of Sb_2Te_3 topological insulator

摘要

We have investigated the temperature dependence of the linear thermal expansion along the hexagonal c axis (△L), in-plane resistivity (ρ), and specific heat (C_ρ) of the topological insulator Sb_2Te_3 single crystal. △L exhibits a clear anomaly in the temperature region 204-236 K. The coefficient of linear thermal expansion α decreases rapidly above 204 K, passes through a deep minimum at around 225 K, and then increases abruptly in the region 225-236 K. a is negative in the interval 221-228 K. The temperature dependence of both α and C_p can be described well by the Debye model from 2 to 290 K, excluding the region around the anomaly in α.