Large-gap quantum spin Hall insulators in tin films

TL;DR

This paper predicts large-gap quantum spin Hall insulators in tin films with potential for room-temperature applications, tunable via chemical and strain modifications, and explores related quantum anomalous Hall effects.

Contribution

It introduces two-dimensional tin films as large-gap QSH insulators with tunable properties, expanding the material options for topological insulators.

Findings

Tin films exhibit a sizable 0.3 eV bulk gap.

QSH states can be tuned by chemical functionalization and strain.

Magnetic doping may induce quantum anomalous Hall effect.

Abstract

The search of large-gap quantum spin Hall (QSH) insulators and effective approaches to tune QSH states is important for both fundamental and practical interests. Based on first-principles calculations we find two-dimensional tin films are QSH insulators with sizable bulk gaps of 0.3 eV, sufficiently large for practical applications at room temperature. These QSH states can be effectively tuned by chemical functionalization and by external strain. The mechanism for the QSH effect in this system is band inversion at the \Gamma point, similar to the case of HgTe quantum well. With surface doping of magnetic elements, the quantum anomalous Hall effect could also be realized.