Tunable moiré excitons induced by proximity effects

Moiré patterns in two-dimensional materials have sparked significant research interest as a platform for exploring unique electronic and excitonic phenomena. Emergent excitons observed in moiré patterns are often attributed to a moiré potential induced by the atomic reconstructions and varying interlayer interaction. Here, we work with a new design principle to create moiré excitons by stacking a monolayer transition metal dichalcogenide on a twisted ferroelectric material. Our ab initio calculations, based on the GW plus Bethe-Salpeter equation approach, reveal two distinct types of novel exciton: one-dimensional Wannier excitons localized at domain boundaries, and spatially separated, charge-transfer-like excitons. The distinct spatial characteristics of these excitons enable one to directly tune their relative excitation energies by manipulating the surrounding dielectric environments. By explicitly accounting for an extrinsic substrate in our calculations, we demonstrate the capability to selectively tune between Wannier and charge-separated excitons, offering a new route to control light-matter interaction and their dephasing for applications in single-photon emission, coherent spin control, and sensing applications.