# Controlling the quantum spin Hall edge states in two-dimensional transition metal dichalcogenides

## TL;DR

This study uses first-principles calculations to analyze the electronic properties of quantum spin Hall edge states in two-dimensional transition metal dichalcogenides, identifying stable edge terminations that isolate helical edge states for potential applications.

## Contribution

It identifies specific stable edge terminations in 2D TMDs that enable the isolation of helical edge states, advancing understanding of QSH phases in these materials.

## Key findings

- Two stable edge terminations isolate helical edge states
- Monolayer 1T'-WSe2 is the most promising material
- Finite-size effects in nanoribbons characterized

## Abstract

Two-dimensional transition metal dichalcogenides (TMDs) of Mo and W in their 1T' crystalline phase host the quantum spin Hall (QSH) insulator phase. We address the electronic properties of the QSH edge states by means of first-principles calculations performed on realistic models of edge terminations of different stoichiometries. The QSH edge states show a tendency to have complex band dispersions and coexist with topologically trivial edge states. We nevertheless identify two stable edge terminations that allow isolating a pair of helical edge states within the band gap of TMDs, with monolayer 1T'-WSe2 being the most promising material. We also characterize the finite-size effects in the electronic structure of 1T'-WSe2 nanoribbons. Our results provide a guidance to the experimental studies and possible practical applications of QSH edge states in monolayer 1T'-TMDs.