Valley contrasting physics in graphene: magnetic moment and topological transport

TL;DR

This paper explores how valley degrees of freedom in graphene exhibit unique magnetic and topological properties, enabling potential valleytronic applications through magnetic and electric manipulation.

Contribution

It demonstrates the intrinsic magnetic moment of valley pseudospin and valley-dependent Berry phase effects leading to contrasting Hall transport in graphene.

Findings

Valley pseudospin has an intrinsic magnetic moment.

Valley-dependent Berry phase causes contrasting Hall effects.

Valley polarization can be generated and detected electrically and magnetically.

Abstract

We investigate physical properties that can be used to distinguish the valley degree of freedom in systems where inversion symmetry is broken, using graphene systems as examples. We show that the pseudospin associated with the valley index of carriers has an intrinsic magnetic moment, in close analogy with the Bohr magneton for the electron spin. There is also a valley dependent Berry phase effect that can result in a valley contrasting Hall transport, with carriers in different valleys turning into opposite directions transverse to an in-plane electric field. These effects can be used to generate and detect valley polarization by magnetic and electric means, forming the basis for the so-called valley-tronics applications.