Floquet electronic bands and transport in magic-angle bilayer graphene

Abstract

We theoretically study Floquet band structures and transport properties of twisted bilayer graphene at the magic-angle under the irradiation of variously polarized light. The magic-angle bilayer graphene is depicted by the newly proposed ten-band tight-binding model and the iterative continued fraction method is adopted to facilitate the calculations of electronic properties in the low-frequency regime. The transitions between Floquet sidebands induce discontinuous electronic bands and energy gaps which further give rise to the antiresonances in longitudinal conductivity calculated by the Kubo formula. Furthermore, significant Hall conductivity is generated by circularly polarized light and its magnitude and sign are sensitive to light polarization as well as photoinduced bandgap-opening, offering a feasible way to tune Hall conductivity by manipulating light polarization. We finally take into account the interplay between light irradiation and short-range disorder, and reveal that disorder scattering remarkably enhances the photoinduced Hall conductivity and can be viewed as an extrinsic source to Hall conductivity.

Keywords

• Floquet theory
• Green function
• twisted bilayer graphene
• Kubo formula