Spin versus charge-density-wave order in graphenelike systems

A variational technique is used to study sublattice symmetry breaking by strong on-site and nearest-neighbor interactions in graphene. When interactions are strong enough to break sublattice symmetry, and with relative strengths characteristic of graphene, a charge-density-wave Mott insulator is favored over the spin-density-wave condensates. In the spin-density-wave condensate we find that introduction of a staggered on-site energy (quasiparticle mass) leads to a splitting of the Fermi velocities and mass gaps of the quasiparticle spin states.