New Quantum Spin Hall Insulator in Two-dimensional MoS$_2$ with Periodically Distributed Pores

TL;DR

This paper predicts a new quantum spin Hall insulator in a porous monolayer MoS$_2$ structure with a large nontrivial gap, expanding the family of TMDs with potential applications in electronics and energy storage.

Contribution

It introduces a novel porous MoS$_2$ allotrope exhibiting QSH effect with a large gap, derived from pure d-d band interactions, confirmed by phonon stability analysis.

Findings

Nontrivial gap of 109 meV in g-MoS$_2$

QSH effect from d-d band interactions

Potential for gas separation and energy storage applications

Abstract

MoS$_2$, one of transition metal dichalcogenides (TMDs), has caused a lot of attentions for its excellent semiconductor characteristics and potential applications. Here, based on the density functional theory methods, we predict a novel 2D quantum spin hall (QSH) insulator in the porous allotrope of monolayer MoS$_2$ (g-MoS$_2$), consisting of MoS$_2$ square and hexagon. The g-MoS$_2$ has a nontrivial gap as large as 109 meV, comparable with previous reported 1T'-MoS$_2$ (80 meV), so-MoS$_2$ (25 meV). We demonstrate that the origin of 2D QSH effect in g-MoS$_2$ originates from the pure d-d band interaction, different from conventional band inversion between s$-$p, p$-$p or d$-$p orbitals. Such new polymorph greatly enriches the TMDs family and its stabilities are confirmed by phonon spectrum analysis. In particular, porous structure also endows it potential application in efficient gas separation and energy storage.