Electrically Tunable Quantum Spin Hall State in Topological Crystalline Insulator Thin films

TL;DR

This paper predicts that (111) thin films of SnTe-class topological crystalline insulators can exhibit a tunable quantum spin Hall phase, controlled by film thickness and external electric fields, offering a promising platform for spintronic applications.

Contribution

It introduces a theoretical prediction of electrically tunable quantum spin Hall states in SnTe TCI thin films based on band topology and electronic structure calculations.

Findings

Quantum spin Hall phase occurs in a wide thickness range.

Electric field can effectively tune the topological phase.

Topological phase transitions are driven by inter-surface coupling sign change.

Abstract

Based on a combination of $k \cdot p$ theory, band topology analysis and electronic structure calculations, we predict the (111) thin films of the SnTe class of three-dimensional (3D) topological crystalline insulators realize the quantum spin Hall phase in a wide range of thickness. The nontrivial topology originates from the inter-surface coupling of the topological surface states of TCI in the 3D limit. The inter-surface coupling changes sign and gives rise to topological phase transitions as a function of film thickness. Furthermore, this coupling can be strongly affected by an external electric field, hence the quantum spin Hall phase can be effectively tuned under experimentally accessible the electric field. Our results show that (111) thin films of SnTe-class TCI can be an ideal platform to realize the novel applications of quantum spin Hall insulators.