Lightwave-driven electrons and high-order harmonic generation in condensed matter

In this work, we focus on calculating the high-order harmonic spectra in two-dimensional hexagonal materials by solving the time-dependent Schr & ouml;dinger equation for a 2x2 tight-binding Bloch Hamiltonian in reciprocal space. Specifically, we apply the Haldane model, which exhibits topological phase transitions based on the hopping amplitudes. Our results demonstrate variations in spectra and electron velocities, depending on the initial high-symmetry point in the Brillouin zone. We particularly emphasize the K and $ K<^>{\prime } $ K ' valleys, which could serve as potential sources of valley currents.