Competing Ordered States in Bilayer Graphene
  We use a perturbative renormalization group approach with short-range continuum model interactions to analyze the competition between isotropic gapped and anisotropic gapless ordered states in bilayer graphene, commenting specifically on the role of exchange and on the importance of spin and valley flavor degeneracy. By comparing the divergences of the corresponding susceptibilities, we conclude that this approach predicts gapped states for flavor numbers N=1,2,4. We also comment briefly on the related gapped states expected in chiral (ABC) trilayer graphene. 
Fan Zhang, Hongki Min, A. H. MacDonald
cond-mat.str-el cond-mat.mes-hall cond-mat.mtrl-sci