Tuning layer-hybridized moire excitons by the quantum-confined Stark effect

Moire superlattices offer an unprecedented opportunity for tailoring interactions between quantum particles(1-11) and their coupling to electromagnetic fields(12-18). Strong superlattice potentials generate moire minibands of excitons(16-18)-bound pairs of electrons and holes that reside either in a single layer (intralayer excitons) or in two separate layers (interlayer excitons). Twist-angle-controlled interlayer electronic hybridization can also mix these two types of exciton to combine their strengths(13,19,20). Here we report the direct observation of layer-hybridized moire excitons in angle-aligned WSe2/WS2 and MoSe2/WS2 superlattices by optical reflectance spectroscopy. These excitons manifest a hallmark signature of strong coupling in WSe2/WS2, that is, energy-level anticrossing and oscillator strength redistribution under a vertical electric field. They also exhibit doping-dependent renormalization and hybridization that are sensitive to the electronic correlation effects. Our findings have important implications for emerging many-body states in two-dimensional semiconductors, such as exciton condensates(21) and Bose-Hubbard models(22), and optoelectronic applications of these materials. Optical reflectance spectroscopy provides a direct observation of layer-hybridized moire excitons in angle-aligned transition metal dichalcogenide heterostructures.