Wavelike dynamics for high harmonic generation in solids

We investigate the wavelike dynamics for high harmonic generation (HHG) in solids. Our results indicate that the wavelike behavior of electrons plays a crucial role in HHG process of solids. In solids, the group velocity dispersion, i.e., the second derivative of energy band, can lead to substantial spatial spread for the evolution of the electron wave packet. This kind of wavelike effect is embedded in the interference of electron-hole wavelets, and allows electrons and holes to be separated spatially when emitting HHG. Incorporating the wavelike effect, we show how one can understand the time-frequency properties of HHG from the perspective of wavelike picture. Furthermore, taking the gapped graphene as a prototype, we also demonstrate that the wavelike picture can well describe the two-dimensional electron dynamics and the emission intensity of HHG. Our analysis provides a comprehensive understanding of the HHG emission properties in solids, and shows how to comprehend the underlying electron dynamics from the perspective of wavelike picture.