Pseudospin Magnetism in Graphene

TL;DR

This paper predicts that neutral graphene bilayers can exhibit pseudospin magnetism, where charge densities from different valleys and spins spontaneously localize in separate layers, leading to novel symmetry-breaking phenomena and potential spintronics applications.

Contribution

It introduces the concept of pseudospin magnetism in graphene bilayers and analyzes the role of momentum-space vortices in symmetry breaking and magnetic behavior.

Findings

Graphene bilayers can spontaneously develop layer-polarized charge densities.

Momentum-space vortices influence the competition between band and kinetic energies.

Hysteresis effects suggest potential for pseudospin-based spintronics.

Abstract

We predict that neutral graphene bilayers are pseudospin magnets in which the charge density-contribution from each valley and spin spontaneously shifts to one of the two layers. The band structure of this system is characterized by a momentum-space vortex which is responsible for unusual competition between band and kinetic energies leading to symmetry breaking in the vortex core. We discuss the possibility of realizing a pseudospin version of ferromagnetic metal spintronics in graphene bilayers based on hysteresis associated with this broken symmetry.