Impurity effects on photo-induced multiply quantized electronic vortices

Previous work on massive two-dimensional Dirac materials has shown that exposing such materials to vortex light beams allows for photo-induced multiply quantized vortex bound states [1]. However, these findings rely on very specific conditions: circularly polarized light and a pristine sample. Our work investigates how robust these vortex bound states are in the presence of cluster and dilute impurities. We analyze impurity effects with a perturbative approach, correcting the quasi-energy and wave functions obtained by exact diagonalization of the Floquet Hamiltonian at the edge of the first Floquet Brillouin zone. The bound states appear to be quite robust to impurities of varying strengths, widths, and placements. We show that while impurity clusters mix vortex bound and bulk states, sharp impurities render small local effects on a limited number of vortex states with minute changes in the local density of states. Our results reflect the “particle-hole” symmetry in the Hamiltonian while the various symmetries present in both the first-order quasi-energy spectra and radial probability distributions are striking manifestations of robust vortex bound states. Our numerical studies suggest that current sample qualities are suitable platforms for the observation of these states.

[1] L.I. Massaro, et. al, PRB 111 085402, (2025)