Floquet engineering and nonequilibrium topological maps in twisted trilayer graphene

Motivated by the recent experimental realization of twisted trilayer graphene and the observed superconductivity that is associated with its flat bands at specific angles, we study trilayer graphene under the influence of different forms of light in the noninteracting limit. Specifically, we study four different types of stacking configurations with a single twisted layer. In all four cases, we study the impact of circularly polarized light and longitudinal light coming from a waveguide. We derive effective time-independent Floquet Hamiltonians and review light-induced changes to the band structure. For circularly polarized light, we find band flattening effects as well as band gap openings. We emphasize that there is a rich band topology, which we summarize in Chern number maps that are different for all four studied lattice configurations. The case of a so-called ABC stacking with top layer twist is especially rich and shows a different phase diagram depending on the handedness of the circularly polarized light. Consequently, we propose an experiment where this difference in typologies could be captured via optical conductivity measurements. In contrast for the case of longitudinal light that is coming from a waveguide, we find that the band structure is very closely related to the equilibrium one but the magic angles can be tuned in situ by varying the intensity of the incident beam of light.

Automated summary

Motivated by recent experiments on twisted trilayer graphene and observed superconductivity, this study examines the effects of different forms of light on trilayer graphene in the noninteracting limit. Circularly polarized light causes band flattening and gap openings, while longitudinal light from a waveguide maintains a closely related band structure but can tune magic angles in situ. The research emphasizes rich band topology and proposes optical conductivity measurements to capture differences in lattice configurations.