Alloying-induced topological transition in 2D transition-metal dichalcogenide semiconductors

TL;DR

This study demonstrates that alloying Os into 2D MoX2 monolayers induces a topological insulator phase with sizable gaps, offering a feasible pathway for experimental realization of 2D TIs.

Contribution

The paper introduces alloying Os into 2D MoX2 monolayers as a novel method to achieve topological insulator states with tunable gaps.

Findings

Alloying Os induces semiconductor-to-TI transition in MoX2 monolayers.

The topological gaps are sizable, ranging from 25 to 37 meV.

External biaxial strain can modulate the TI gaps.

Abstract

Research on two-dimensional (2D) topological insulators (TIs) is obstructed due to the lack of feasible approaches to growing 2D TIs in experiments. Through systematic first-principles calculations and tight-binding simulations, we propose that alloying Os in 2D MoX2 (X = S, Se, Te) monolayers is an effective approach to inducing semiconductor-to-TI transitions, with sizable nontrivial gaps of 25-37 meV. Analysis of the electronic structures reveals that the topological property mainly originates from the 5d orbitals of the Os atom. Furthermore, the TI gaps can be modulated by external biaxial strain.