Comparison of high-order harmonic generation in finite and bulk honeycomb lattices

The high-order harmonic generation in solid systems has been studied extensively in recent years. Most of the theoretical work focuses on the bulk of solids. Hence, edge effects, as in realistic systems, are neglected. In this work we provide a direct comparison of the harmonic spectra from finite systems and the bulk. The investigated systems are two-dimensional honeycomb lattices with either one (e.g., graphene) or two (e.g., hexagonal boron nitride) different atomic elements contained in the system. The calculation of the momentum-resolved spectra allows a deep insight of the electron dynamics inside the bandstructure and in position space. Electrons might be forced to move along the edges in the finite system if the incident laser is circularly polarized. In the bulk, such edge currents cannot occur.