Optical Injection and Detection of Long-Lived Interlayer Excitons in van der Waals Heterostructures.

Interlayer excitons in semiconducting bilayers separated by insulating hexagonal boron nitride (h-BN) layers constitute a promising platform for investigation of strongly correlated bosonic phases. Here, we report an optical method for the generation and characterization of long-lived interlayer excitons. We confirm the presence of tightly bound interlayer excitons by measuring 1s and 2s intralayer excitons in each layer concurrently. Using a pump-probe technique, we find interlayer exciton lifetimes up to 8.8  μs, increasing with the thickness of the h-BN. With optical access to long-lived interlayer excitons, our approach provides a new route to explore degenerate Bose-Fermi mixtures of excitons and itinerant electrons with high spatial and temporal resolution.