Strain induced $\mathbb{Z}_2$ topological insulating state of $\beta$-As$_2$Te$_3$

TL;DR

This study predicts a strain-induced topological phase transition in $eta$-As$_2$Te$_3$, transforming it from a trivial insulator to a topological insulator with potential applications in sensors and thermoelectrics.

Contribution

First-principles calculations reveal a uniaxial strain induced topological transition in $eta$-As$_2$Te$_3$, including a Weyl metallic state and band inversion.

Findings

Topological transition occurs at uniaxial strain $oxed{-0.05}$

Weyl metallic state with a Dirac cone at $oxed{ ext{Gamma}}$ point

Change in $oxed{ u_0}$ from 0 to 1

Abstract

Topological insulators are non-trivial quantum states of matter which exhibit a gap in the electronic structure of their bulk form, but a gapless metallic electronic spectrum at the surface. Here, we predict a uniaxial strain induced electronic topological transition (ETT) from a band to topological insulating state in the rhombohedral phase (space group: R$\bar{3}$m) of As$_2$Te$_3$ ($\beta$-As$_2$Te$_3$) through \textit{first-principles} calculations including spin-orbit coupling within density functional theory. The ETT in $\beta$-As$_2$Te$_3$ is shown to occur at the uniaxial strain $\epsilon_{zz}$ = -0.05 ($\sigma_{zz}$=1.77 GPa), passing through a Weyl metallic state with a single Dirac cone in its electronic structure at the $\Gamma$ point. We demonstrate the ETT through band inversion and reversal of parity of the top of the valence and bottom of the conduction bands leading to change in the $\mathbb{Z}_2$ topological invariant $\nu_0$ from 0 to 1 across the transition. Based on its electronic structure and phonon dispersion, we propose ultra-thin films of As$_2$Te$_3$ to be promising for use in ultra-thin stress sensors, charge pumps and thermoelectrics.