Half Metallic Bilayer Graphene

TL;DR

This paper proposes that lightly charged bilayer graphene under an electric field can become a half metal due to symmetry breaking in the layered antiferromagnetic state, supported by mean field theory analysis.

Contribution

It introduces the possibility of half metallic behavior in bilayer graphene induced by electric field and charge doping, based on a mean field theoretical model.

Findings

Lightly charged bilayer graphene can exhibit half metallic behavior.

Electric field breaks inversion and particle-hole symmetry in the LAF state.

Mean field theory supports the emergence of half metal in this system.

Abstract

Charge neutral bilayer graphene has a gapped ground state as transport experiments demonstrate. One of the plausible such ground states is layered antiferromagnetic spin density wave (LAF) state, where the spins in top and bottom layers have same magnitude with opposite directions. We propose that lightly charged bilayer graphene in an electric field perpendicular to the graphene plane may be a half metal as a consequence of the inversion and particle-hole symmetry broken in the LAF state. We show this explicitly by using a mean field theory on a 2-layer Hubbard model for the bilayer graphene.