Engineering a robust quantum spin Hall state in graphene via adatom deposition

TL;DR

This paper proposes a method to induce a robust quantum spin Hall state in graphene by depositing heavy adatoms, potentially enabling new electronic and quantum devices with topological properties.

Contribution

The authors provide a theoretical blueprint for stabilizing a topological insulator phase in graphene using heavy adatoms, supported by symmetry, DFT, and tight-binding calculations.

Findings

Heavy adatoms can induce a sizable topological band gap in graphene.

A 6% coverage of indium or thallium yields gaps of approximately 80K and 240K.

The predicted topological phase is detectable via transport or spectroscopic methods.

Abstract

The 2007 discovery of quantized conductance in HgTe quantum wells delivered the field of topological insulators (TIs) its first experimental confirmation. While many three-dimensional TIs have since been identified, HgTe remains the only known two-dimensional system in this class. Difficulty fabricating HgTe quantum wells has, moreover, hampered their widespread use. With the goal of breaking this logjam we provide a blueprint for stabilizing a robust TI state in a more readily available two-dimensional material---graphene. Using symmetry arguments, density functional theory, and tight-binding simulations, we predict that graphene endowed with certain heavy adatoms realizes a TI with substantial band gap. For indium and thallium, our most promising adatom candidates, a modest 6% coverage produces an estimated gap near 80K and 240K, respectively, which should be detectable in transport or spectroscopic measurements. Engineering such a robust topological phase in graphene could pave the way for a new generation of devices for spintronics, ultra-low-dissipation electronics and quantum information processing.