Functionalized Thallium Antimony Films as Excellent Candidates for Large-Gap Quantum Spin Hall Insulator

TL;DR

This paper predicts functionalized TlSb monolayers as large-gap quantum spin Hall insulators with tunable properties, suitable for spintronics and quantum computing applications.

Contribution

It introduces a new class of large-gap QSH insulators in functionalized TlSb monolayers with tunable electronic properties and stability on BN substrates.

Findings

Bulk gaps as large as 0.22-0.40 eV identified.

QSH states confirmed by Z2 invariant and edge states.

Electric field and strain can tune the band gap.

Abstract

Group III-V films are of great importance for their potential application in spintronics and quantum computing. Search for two-dimensional III-V films with a nontrivial large-gap are quite crucial for the realization of dissipationless transport edge channels using quantum spin Hall (QSH) effects. Here we use first-principles calculations to predict a class of large-gap QSH insulators in functionalized TlSb monolayers (TlSbX2; (X = H, F, Cl, Br, I)), with sizable bulk gaps as large as 0.22~0.40 eV. The QSH state is identified by Z2 topological invariant together with helical edge states induced by spin-orbit coupling (SOC). Noticeably, the inverted band gap in the nontrivial states can be effectively tuned by the electric field and strain. Additionally, these films on BN substrate also maintain a nontrivial QSH state, which harbors a Dirac cone lying within the band gap. These findings may shed new light in future design and fabrication of QSH insulators based on two-dimensional honeycomb lattices in spintronics.