Theoretical investigation of the evolution of the topological phase of Bi$_{2}$Se$_{3}$ under mechanical strain

TL;DR

This paper investigates how mechanical strain influences the topological phase of Bi$_2$Se$_3$, revealing that strain affects both Coulombic and spin-orbit interactions, which can be used to control its topological properties.

Contribution

The study provides a detailed theoretical analysis of strain effects on Bi$_2$Se$_3$'s topological phase, highlighting the importance of both Coulombic and spin-orbit interactions in this process.

Findings

Compressive strain decreases Coulombic gap but increases spin-orbit interaction.

Strain can be used to manipulate the topological phase of Bi$_2$Se$_3$.

Comparison with Bi$_2$Te$_3$ emphasizes the role of both interactions.

Abstract

The topological insulating phase results from inversion of the band gap due to spin-orbit coupling at an odd number of time-reversal symmetric points. In Bi$_2$Se$_3$, this inversion occurs at the $\Gamma$ point. For bulk Bi$_2$Se$_3$, we have analyzed the effect of arbitrary strain on the $\Gamma$ point band gap using Density Functional Theory. By computing the band structure both with and without spin-orbit interactions, we consider the effects of strain on the gap via Coulombic interaction and spin-orbit interaction separately. While compressive strain acts to decrease the Coulombic gap, it also increases the strength of the spin-orbit interaction, increasing the inverted gap. Comparison with Bi$_2$Te$_3$ supports the conclusion that effects on both Coulombic and spin-orbit interactions are critical to understanding the behavior of topological insulators under strain, and we propose that the topological insulating phase can be effectively manipulated by inducing strain through chemical substitution.