Moiré quantum electrodynamics

We study a moiré material sandwiched between two linearly responsive, passive, spatially local, and isotropic magnetoelectric media forming a stratified planar geometry. The moiré material enters through the boundary condition between the two magnetoelectric regions. In particular, this encodes a microscopic description of the condensed matter system via a moiré-modulated, in-plane, optical conductivity. We obtain the Green's tensor of such an interface within a macroscopic quantum electrodynamics framework. Our approach captures local-field-effects. These are reflected in the structure of the generalized Fresnel coefficients that determine the Umklapp-allowed photon scattering processes in this platform. We illustrate our formalism by studying the coupling of emitters to a twisted bilayer graphene setting and show how emitter-emitter interactions can be dressed by this non-trivial environment. Exploring the quantum optical behavior of such a light-matter interface offers an alternative route to elucidate exotic phenomena in moiré systems.