Chern insulating phases in a cavity-embedded kagome system

We investigate topological band structures of a kagome system embedded in a chiral cavity. We show that Chern insulating phases emerge in the cavity-embedded kagome system due to the light-matter interaction that breaks time-reversal symmetry. Moreover, a nearly flat band can become topologically nontrivial, characterized by a nonzero Chern number. By changing the light-matter interaction, we reveal that topological phase transitions occur between different Chern insulating phases in the ultrastrong coupling regime. We also demonstrate the existence of topological boundary modes in the cavity-embedded kagome Chern insulators by constructing a low-energy tight-binding model.