Cavity vacuum control of topological transition in a full filling moiré superlattice*

The interaction between quasiparticles in condensed matter systems induced by exchanging virtual photons has attracted widespread interest because it leads to remarkable and exotic phases of matter. Such virtual-photon-mediated interaction is typically investigated in a strong light-matter coupling regime realized in a metallic split-ring terahertz (THz) electromagnetic resonator. Moiré superlattice embedded in a THz resonator is a suitable system to explore cavity control at frequency down to the Terahertz range. Here we study the topological transition in cavity-embedded moiré superlattice doped at filling factor 1 (one electron/hole per supercell). Within the mean-field approximation, we show that the virtual-photon-mediated interaction can introduce a topological band inversion, namely the electronic system can be in the topological trivial (nontrivial) states in the absence (presence) of the cavity in a vacuum. The cavity vacuum-mediated interaction Hamiltonian provides a topological nontrivial mass term, which is also gate-tunable. Our results point to a promising new toolbox for manipulating topological transition.