Anomalous thermal expansion of Sb$_2$Te$_3$ topological insulator

TL;DR

This study investigates the unusual thermal expansion behavior of Sb$_2$Te$_3$ topological insulator, revealing an anomaly between 204-236 K, with implications for understanding its thermal properties.

Contribution

The paper reports the first detailed analysis of anomalous thermal expansion in Sb$_2$Te$_3$, linking it to specific heat and resistivity measurements and modeling with the Debye model.

Findings

Anomaly in thermal expansion coefficient between 204-236 K

Negative thermal expansion observed between 221-228 K

Debye model describes thermal properties outside the anomaly region

Abstract

We have investigated the temperature dependence of the linear thermal expansion along the hexagonal c axis ($\Delta L$), in-plane resistivity ($\rho$), and specific heat ($C_p$) of the topological insulator Sb$_2$Te$_3$ single crystal. $\Delta L$ exhibits a clear anomaly in the temperature region 204-236 K. The coefficient of linear thermal expansion $\alpha$ decreases rapidly above 204 K, passes through a deep minimum at around 225 K and then increases abruptly in the region 225-236 K. $\alpha$ is negative in the interval 221-228 K. The temperature dependence of both $\alpha$ and $C_p$ can be described well by the Debye model from 2 to 290 K, excluding the region around the anomaly in $\alpha$.