Real-space multifold degeneracy in graphene irradiated by twisted circularly polarized light

We study monolayer graphene coherently driven by twisted light carrying orbital angular momentum and a radial vortex profile. Using Floquet theory, we characterize the real-space structure of quasienergies and Floquet modes. We obtain the effective real-space Floquet Hamiltonian and show it supports crossings of Floquet modes, associated with high-symmetry K and Γ points of graphene, at specific radial positions from the vortex center. This yields a ring of vortex bound states whose number is a topological invariant. These bound states form a multifold degenerate structure in real space that is purely dynamically generated and controlled by the frequency and intensity of twisted light.