Symmetry control of high-harmonic generation in bilayer hexagonal boron nitride

In this study, we explored the generation of high-order harmonics in two-dimensional hexagonal boron nitride using the semiconductor Bloch equations. Our analysis reveals that the harmonic selection rules are determined by the temporal and spatial symmetries present in both the laser and the materials. We conducted calculations with both monolayer and bilayer hexagonal boron nitride as prototypical examples. The results demonstrate a pronounced sensitivity of the generated harmonics to the laser’s ellipticity and polarization. In addition, we established that group theory, integrating the temporal–spatial symmetries of the laser and the materials, can accurately predict permissible harmonic orders. This research could be useful for investigating lattice symmetry and manipulating electronic dynamics in multilayer two-dimensional materials.