  Moir\'e superlattices open an unprecedented opportunity for tailoring
interactions between quantum particles and their coupling to electromagnetic
fields. Strong superlattice potential generates moir\'e minibands of excitons
-- bound pairs of electrons and holes that reside either in a single layer
(intralayer excitons) or two separate layers (interlayer excitons). The
twist-angle-controlled interlayer hybridization of carriers can also mix the
two types of excitons to combine the strengths of both. Here, we report a
direct observation of spatially mixed moir\'e excitons in angle-aligned
WSe2/WS2 and MoSe2/WS2 superlattices by optical reflectance spectroscopy. The
strongly interacting interlayer and intralayer moir\'e excitons in WSe2/WS2
manifest energy level anticrossing and oscillator strength redistribution under
a vertical electric field. We also observe doping-dependent exciton miniband
renormalization and mixing near half filling of the first electron miniband of
WS2. Our findings have significant implications for emerging correlated states
in two-dimensional semiconductors, such as exciton condensates and Bose-Hubbard
models, and optoelectronic applications of these materials.
