When the Coulomb interaction becomes strong in semiconductors, the electrons and holes can interact to form excitonic states, which govern the materials’ optical properties. In atomically thin transition metal dichalcogenide (TMD) devices encapsulated by boron nitride, we observe various excitonic states with distinctive spin and valley configurations, including the bright and dark excitons, and intra- and inter-valley excitons. These excitons exhibit complex interactions with photons and phonons, giving rise to a panoply of emission lines. We have tailored the excitonic properties by using the charge density, magnetic field, and moiré potential. These novel excitonic states with adjustable properties hold promises for the development of next-generation excitonic devices.
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