Quantum spin Hall insulator phase in monolayer WTe2 by uniaxial strain

Hui Xiang,Zhiguo Liu,Haiming Lu,Jinqiu Liu,Yidong Xia,Bo Xu,Jiang Yin

doi:10.1063/1.4962662

Abstract

Monolayer WTe2, which is predicted to be large-gap quantum spin Hall (QSH) insulators with distorted 1T (1T’) structure, attracts rapidly growing interests. However, the intrinsic semimetallic nature of the monolayer 1T’-WTe2 limits their direct applications based on QSH effect. By first-principles density functional theoretical calculations, we demonstrate a phase transition from semimetal to QSH insulator under the uniaxial strains along a and b axis in monolayer 1T’-WTe2. The electronic phase transition results from the geometric structure deformation upon the uniaxial strains. This suggests monolayer 1T’-WTe2 as a promising material for application in strain-tunable topological quantum electronics.

Highlights

Quantum spin Hall (QSH) insulators[1,2,3] have an insulating bulk but conducting edge states that are topologically protected from backscattering by time reversal symmetry, which could provide an alternative route to quantum electronic devices with low dissipation
Monolayer MX2 transition-metal dichalcogenides (TMDCs) possess a variety of polytypic structures such as 2H, 1T, and 1T’
The ground-state structure of monolayer WTe2 is 1T’, which consists of buckled sheets of Te atoms, with the W atoms residing in distorted octahedral sites, as displayed in larger than that in tungsten metal (2.74 Å)

Summary

Introduction

Quantum spin Hall (QSH) insulators[1,2,3] have an insulating bulk but conducting edge states that are topologically protected from backscattering by time reversal symmetry, which could provide an alternative route to quantum electronic devices with low dissipation. The QSH effect has been observed in several materials, such as HgTe/CdTe4 and InAs/GaSb5 quantum-well structures. Both of them require extreme conditions, such as the precisely controlled molecular-beam epitaxy (MBE) and the ultralow temperature attributed to the small band gap of the order of meV, which greatly obstructs further experimental studies and possible applications. The semimetallic nature of bulk WTe2 with 1T’ structure was reported by Ali et al.[16] in experiment. They discovered an extremely large magnetoresistance (XMR) at low

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