Emergent antiferromagnetism in Y-shaped Kekul? graphene

Antiferromagnetic (AFM) transitions of birefringent Dirac fermions created by a Y-shaped Kekule distortion in graphene are investigated by mean-field theory and determinant quantum Monte Carlo simulations. We show that the quantum critical point can be continuously tuned by the bond-modulation strength, and the universality of the quantum criticality remains in the Gross-Neveu-Heisenberg class. The critical interaction scales with the geometric average of the two velocities of the birefringent Dirac cones, and decreases monotonically between the uniform and completely depleted limits. Since the AFM critical interaction can be tuned to very small values, antiferromagnetism may emerge automatically, realizing the long-sought magnetism in graphene. These results enrich our understanding of the semimetal-AFM transitions in Dirac-fermion systems, and open a route to achieve magnetism in graphene.