Nonlinear optical response in band-gapped graphene-like materials.

Density-functional theory is performed to obtain the unperturbed band structure for a range of band-gap graphene-like surfaces. The interband multiphoton transitions of these systems are studies using the non-perturbative Fluoquet-Liouville supermatrix approach. Quasienergy band structures are used to calculate the single- and multiple-photon absorption spectra. We will discuss the implications for the observed Floquet-Bloch states in time- and angle-resolved photoemission spectroscopy.