Weak topological insulators induced by the inter-layer coupling: A first-principles study of stacked Bi2TeI

TL;DR

This study predicts Bi2TeI as a weak topological insulator with unique isotropic Dirac surface states due to strong inter-layer coupling, and demonstrates its potential as a robust quantum spin Hall system.

Contribution

First-principles prediction of Bi2TeI as a weak topological insulator with distinctive surface states and stability for quantum spin Hall applications.

Findings

Bi2TeI is a weak topological insulator with an 80 meV gap.

Existence of isotropic Dirac-cone-like surface states.

Sandwiched BiTeI-Bi2-BiTeI structure is a stable quantum spin Hall system.

Abstract

Based on first-principles calculations, we predict Bi2TeI, a stoichiometric compound synthesized, to be a weak topological insulator (TI) in layered subvalent bismuth telluroiodides. Within a bulk energy gap of 80 meV, two Dirac-cone-like topological surface states exist on the side surface perpendicular to BiTeI layer plane. These Dirac cones are relatively isotropic due to the strong inter-layer coupling, distinguished from those of previously reported weak TI candidates. Moreover, with chemically stable cladding layers, the BiTeI-Bi2-BiTeI sandwiched structure is a robust quantum spin Hall system, which can be obtained by simply cleaving the bulk Bi2TeI.