Possible half-metallic phase in bilayer graphene: Calculations based on mean-field theory applied to a two-layer Hubbard model

Charge neutral bilayer graphene has a gapped ground state, as transport experiments have demonstrated. One plausible ground state is the layered antiferromagnetic spin density wave (LAF) state, where the spins in the top and bottom layers have the 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. We show this explicitly by using a mean-field theory on a two-layer Hubbard model.