Topological insulators with unexpectedly HgTe-like band inversion in hexagonal wurtzite-type binary compounds

Abstract

By using first-principles calculations, we propose a new topological insulator family in hexagonal wurtzite-type binary compounds. As a result, we found that two compounds AuI and strained-AgI are three-dimensional topological insulators with a naturally opened band gap at the Fermi level. By considering the band inversion mechanism, this new family of topological insulators shows an unexpectedly HgTe-like, i.e., band inversion. These findings suggest that, in these wurtzite-type compounds, the spin-orbit coupling may not play a crucial role in the band inversion mechanism; on the contrary, it is mainly responsible for the formation of the global band gaps. We further theoretically explore the feasibility of tuning the topological order of the wurtzite compounds AuI and AgI with two types of strains (hydrostatic and uniaxial). The results indicate that the uniaxial strain can significantly influence the band inversion behavior and the underlying physical mechanism is discussed.