UC Berkeley

Moir e superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures. The moir e effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moir e superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moir e quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moir e sites. Here we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moir e superlattice and unambiguously determine their spin, valley, and moir e QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moir e sites can exhibit opposite optical selection rules due to the spatially-varying moir e QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moir e superlattices for optoelectronic and valleytronic applications.