Quantum Spin Hall Effect in 2D Transition Metal Dichalcogenide Haeckelites

TL;DR

This paper predicts that certain 2D transition metal dichalcogenide haeckelites with square-octagonal lattices can exhibit quantum spin Hall effect, with large band gaps suitable for room-temperature applications, supported by first-principles calculations and a new tight-binding model.

Contribution

It introduces a new class of 2D topological insulators based on square-like lattice structures, expanding the material system beyond honeycomb lattices.

Findings

Predicted quantum spin Hall effect in $MX_2$-4-8 haeckelites.

Largest band gap around 54 meV, higher than room temperature.

Established a simple tight-binding model for topological states.

Abstract

By using first-principles calculation, we have found that a family of 2D transition metal dichalcogenide haeckelites with square-octagonal lattice $MX_2$-4-8 ($M$=Mo, W and $X$=S, Se and Te) can host quantum spin hall effect. The phonon spectra indicate that they are dynamically stable and the largest band gap is predicted to be around 54 meV, higher than room temperature. These will pave the way to potential applications of topological insulators. We have also established a simple tight-binding model on a square-like lattice to achieve topological nontrivial quantum states, which extends the study from honeycomb lattice to square-like lattice and broads the potential topological material system greatly.