Dependence of high-harmonic generation in twisted bilayer graphene on laser pulse ellipticity

The ellipticity of a laser pulse offers a control knob to tune the efficiency and polarization of emitted higher-order harmonics. In this paper, we systematically investigate the ellipticity dependence of high-harmonic generation in various bilayer graphene systems, such as AA-stacked, AB-stacked, and twisted bilayer graphene. We demonstrate how the underlying symmetries and electronic band structures of different bilayer systems distinctly contribute to the characteristics of ellipticity dependence, such as elliptical enhancement and elliptical dichroism. Additionally, we showcase a unique applicability of high-harmonic spectroscopy as a tool for identifying stacking faults in bilayer graphene systems. Our findings offer valuable insights into the nonlinear optical interactions of twisted bilayer graphene with different twist angles. Published by the American Physical Society 2024