Stacking order, interaction, and weak surface magnetism in layered graphene sheets

Abstract

Recent transport experiments have demonstrated that rhombohedral-stacking trilayer graphene is an insulator with an intrinsic gap of 6 meV and Bernal-stacking trilayer graphene is a metal. We propose a Hubbard model with a moderate $U$ for layered graphene sheets, and show that the model well explains the experiments on the stacking-dependent energy gap. The moderate on-site Coulomb repulsion drives the metallic phase of the noninteracting system to a weak surface antiferromagnetic insulator for the rhombohedral stacking layers, while the interaction-opened energy gaps for the Bernal stacking layers are much smaller.