Topological Insulators in Hexagonal Wurtzite-type Binary Compounds

TL;DR

This paper predicts new three-dimensional topological insulators in hexagonal wurtzite-type compounds, specifically AgI and AuI, using first-principles calculations, and explores how strain can induce topological phase transitions.

Contribution

It introduces a new family of topological insulators in hexagonal wurtzite compounds and analyzes their band inversion mechanisms and strain-induced topological phase transitions.

Findings

AgI and AuI are topological insulators with a natural band gap.

Spin-orbit coupling mainly influences the band gap, not the band inversion.

Uniaxial strain can induce topological phase transitions.

Abstract

We propose new topological insulators in hexagonal wurtzite-type binary compounds based on the first principles calculations. It is found that two compounds AgI and AuI are three-dimensional topological insulators with a naturally opened band-gap at Fermi level. From band inversion mechanism point view, this new family of topological insulators is similar with HgTe, which has s (Gamma 6) - p (Gamma 8) band inversion. Our results strongly support that the spin-orbit coupling is not an essential factor to the band inversion mechanism; on the contrary, it is mainly responsible to the formation of a global band gap for the studied topological insulators. We further theoretically explore the feasibility of tuning the topological order of the studied compounds with two types of strains. The results show that the uniaxial strain can contribute extremely drastic impacts to the band inversion behavior, which provide an effective approach to induce topological phase transition.