The rhombohedral Sb2Se3 is also an intrinsic topological insulator

TL;DR

This paper demonstrates through first-principles calculations that rhombohedral Sb2Se3 is an intrinsic topological insulator with protected surface states, expanding the class of known topological materials.

Contribution

It reveals that Sb2Se3, previously overlooked, exhibits topologically protected surface states when van der Waals interactions are considered, with a bulk gap of 0.19 eV.

Findings

Sb2Se3 has a bulk gap of 0.19 eV.

Topologically protected surface states appear at six quintuple layers.

Van der Waals interactions are crucial for the topological properties.

Abstract

Topological insulators are new class of quantum materials, which have insulating energy gaps in bulk, but exhibit gapless edge states or surface states that are protected by time-reversal symmetry at boundary. It was theoretically predicted and experimentally confirmed that the binary tetradymites Bi2Te3, Bi2Se3, and Sb2Te3 are three-dimensional topological insulators. In this work, we demonstrate by first-principles approach that the ignored Sb2Se3, although with relatively smaller spin-orbital coupling strength, can also exhibit topologically protected surface states with a bulk gap of 0.19 eV, as long as the van der Waals interaction is explicitly included in the calculations. Detailed analysis of the band structures of Sb2Se3 thin films indicates that the non-trivial surface state appears at a critical thickness of six quintuple layers.