Two-color nonlinear optical response of graphene with broken AB-symmetry

We demonstrate that the bandgap opening in graphene induced by AB-sublattice symmetry breaking leads to a strong nonlinear optical response for frequencies well below the bandgap where linear response is strictly forbidden. Our result suggests that one type of graphene with such symmetry breaking, semihydrogenated graphene, can have a unique potential as a two-color nonlinear material in the terahertz photonics.