Distant-neighbor hopping in graphene and Haldane models

Large Chern number phases in a Haldane model become possible if there is a multiplication of Dirac points in the underlying graphene model. This is realized by considering long-distance hopping integrals. Through variation of these integrals, it is possible to arrive at supermerging band touchings, which up to N7 graphene are unique in parameter space. They result from the synchronized motion of all supplementary Dirac points into the regular +/- K points of graphene. The energy dispersion power law is usually larger than the topological charge associated with them. Moreover, adding distant-neighbor hoppings in the Haldane mass allows one to sweep large Chern number phases in the topological insulator. DOI: 10.1103/PhysRevB.87.115402