New Family of Robust 2D Topological Insulators in van der Waals Heterostructures

TL;DR

This paper predicts a new family of robust 2D topological insulators in van der Waals heterostructures combining graphene and BiTeX, with large energy gaps and potential for innovative electronic devices.

Contribution

It introduces a novel class of 2D topological insulators in van der Waals heterostructures with large, tunable energy gaps confirmed by first principles calculations.

Findings

Intrinsic topologically nontrivial bulk energy gaps of 70-80 meV

Energy gaps can be enhanced up to 120 meV by compression

Presence of metallic edge states confirmed by calculations

Abstract

We predict a new family of robust two-dimensional (2D) topological insulators in van der Waals heterostructures comprising graphene and chalcogenides BiTeX (X=Cl, Br and I). The layered structures of both constituent materials produce a naturally smooth interface that is conducive to proximity induced new topological states. First principles calculations reveal intrinsic topologically nontrivial bulk energy gaps as large as 70-80 meV, which can be further enhanced up to 120 meV by compression. The strong spin-orbit coupling in BiTeX has a significant influence on the graphene Dirac states, resulting in the topologically nontrivial band structure, which is confirmed by calculated nontrivial Z2 index and an explicit demonstration of metallic edge states. Such heterostructures offer an unique Dirac transport system that combines the 2D Dirac states from graphene and 1D Dirac edge states from the topological insulator, and it offers new ideas for innovative device designs.