A proposal for optical control of topological memory in Chern insulators realized in moiré multilayers

Under suitable experimental conditions, some twisted graphene multilayers and transition-metal dichalcogenides become Chern insulators. They exhibit the anomalous quantum Hall effect and orbital magnetization due to spontaneous valley polarization. We study (theoretically) the interaction of a Chern insulator with circularly polarized light derived from the optical Stark energy shift. The interaction energy contains an antisymmetric term that couples the helicity of incident light and the Berry curvature of the electronic system. Taking advantage of this interaction, we propose optical switching of the sign of the Chern number, representing topological memory, by circularly polarized light. Moreover, two laser beams of opposite circular polarization can nucleate domains of opposite magnetization and thus produce an optically-configurable domain wall carrying topologically protected chiral edge modes.