Strain Tunable Semimetal-Topological-Insulator Transition in Monolayer 1T'-WTe2

TL;DR

This paper demonstrates how strain engineering can induce a transition from a semimetallic to an insulating phase in monolayer 1T'-WTe2, revealing a tunable topological phase with robust edge states.

Contribution

It introduces a strain-based method to control the topological phase transition in monolayer 1T'-WTe2, confirmed by experimental techniques.

Findings

Strain can induce a full gap insulating phase in 1T'-WTe2.

Topological edge states remain robust under strain.

Experimental confirmation of phase transition via microscopy and spectroscopy.

Abstract

A quantum spin hall insulator(QSHI) is manifested by its conducting edge channels that originate from the nontrivial topology of the insulating bulk states. Monolayer 1T'-WTe2 exhibits this quantized edge conductance in transport measurements, but because of its semimetallic nature, the coherence length is restricted to around 100 nm. To overcome this restriction, we propose a strain engineering technique to tune the electronic structure, where either a compressive strain along a axis or a tensile strain along b axis can drive 1T'-WTe2 into an full gap insulating phase. A combined study of molecular beam epitaxy and in-situ scanning tunneling microscopy/spectroscopy then confirmed such a phase transition. Meanwhile, the topological edge states were found to be very robust in the presence of strain.