A scheme to realize the quantum spin-valley Hall effect in monolayer graphene

TL;DR

This paper proposes a method to realize the quantum spin-valley Hall effect in monolayer graphene through quantum pumping, enabling spin and valley current control without relying on spin-orbit interaction.

Contribution

It introduces a novel scheme to generate quantum spin-valley Hall effect in graphene via adiabatic modulation, bypassing the need for intrinsic spin-orbit coupling.

Findings

Exclusive spin-polarized currents in opposite directions in two valleys.

Pure spin currents flowing oppositely in the two valleys.

Simultaneous probing of quantum valley and spin Hall effects.

Abstract

Quantum spin Hall effect was first predicted in graphene. However, the weak spin orbit interaction in graphene meant that the search for quantum spin Hall effect in graphene never fructified. In this work we show how to generate the quantum spin-valley Hall effect in graphene via quantum pumping by adiabatically modulating a magnetic impurity and an electrostatic potential in a monolayer of strained graphene. We see that not only exclusive spin polarized currents can be pumped in the two valleys in exactly opposite directions but one can have pure spin currents flowing in opposite directions in the two valleys, we call this novel phenomena the quantum spin-valley Hall effect. This means that the twin effects of quantum valley Hall and quantum spin Hall can both be probed simultaneously in the proposed device. This work will significantly advance the field of graphene spintronics, hitherto hobbled by the lack of spin-orbit interaction. We obviate the need for any spin orbit interaction and show how graphene can be manipulated to posses features exclusive to topological insulators.