Effect of hydrostatic pressure on transport in the topological insulator Bi$_2$Te$_2$Se

TL;DR

This study investigates how hydrostatic pressure influences electrical transport properties in the topological insulator Bi$_2$Te$_2$Se, revealing pressure-induced decreases in a transport gap and hole effective mass.

Contribution

It introduces a model explaining the non-monotonic temperature dependence of Hall coefficient and resistivity, incorporating effects of pressure on the transport gap and effective mass.

Findings

Hydrostatic pressure reduces the transport gap $\

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Abstract

The Hall coefficient $R_H$ and resistivity $\rho$ of the topological insulator Bi$_2$Te$_2$Se display a number of puzzling features vs. temperature $T$. We propose a model that describes well the non-monotonic variation of $R_H(T)$. A key feature of the model is a chemical potential that is weakly $T$-dependent. From the fit to the model, we infer a "transport" gap $\Delta_T$ of 50 mV. We find that hydrostatic pressure $P$ (0-27 kbar) has a pronounced effect on both $R_H$ and $\rho$. We show that these changes arise from decreases in both $\Delta_T$ and the hole effective mass under pressure.