Quantum Spin Hall Effect in Graphene

TL;DR

This paper demonstrates that spin orbit interactions can induce a quantum spin Hall insulator state in graphene, characterized by topologically protected edge states that support quantized spin and charge transport.

Contribution

It reveals that graphene can become a quantum spin Hall insulator due to spin orbit coupling, a novel phase not previously observed in this material.

Findings

Graphene can transition to a quantum spin Hall insulator with spin orbit interactions.

Edge states in this phase are non chiral but protected against disorder.

Quantized spin and charge conductance are supported by these edge states.

Abstract

We study the effects of spin orbit interactions on the low energy electronic structure of a single plane of graphene. We find that in an experimentally accessible low temperature regime the symmetry allowed spin orbit potential converts graphene from an ideal two dimensional semimetallic state to a quantum spin Hall insulator. This novel electronic state of matter is gapped in the bulk and supports the quantized transport of spin and charge in gapless edge states that propagate at the sample boundaries. The edge states are non chiral, but they are insensitive to disorder because their directionality is correlated with spin. The spin and charge conductances in these edge states are calculated and the effects of temperature, chemical potential, Rashba coupling, disorder and symmetry breaking fields are discussed.