Bound states of conical singularities in graphene-based topological insulators

We investigate the electronic structure induced by wedge disclinations (conical singularities) in a honeycomb lattice model realizing Chern numbers γ = ± 1. We establish a correspondence between the bound state of (i) an isolated Φ(0)/2 flux, (ii) an isolated pentagon (n = 1) or heptagon (n = -1) defect with an external flux of magnitude nγΦ(0)/4 through the center, and (iii) an isolated square or octagon defect without external flux, where Φ(0) = h/e is the flux quantum. Because of the above correspondence, the existence of isolated electronic states bound to disclinations is robust against various perturbations. Hence, measuring these defect states offers an interesting probe of graphene-based topological insulators which is complementary to measurements of the quantized edge currents.