  The elementary optical excitations in two dimensional semiconductors hosting
itinerant electrons are attractive and repulsive polarons -- excitons that are
dynamically screened by electrons. Exciton-polarons have hitherto been studied
in translationally invariant degenerate Fermi systems. Here, we show that
electronic charge order breaks the excitonic translational invariance and leads
to a direct optical signature in the exciton-polaron spectrum. Specifically, we
demonstrate that new optical resonances appear due to spatially modulated
interaction between excitons and electrons in an incompressible Mott state. Our
observations demonstrate that resonant optical spectroscopy provides an
invaluable tool for studying strongly correlated states, such as Wigner
crystals and density waves, where exciton-electron interactions are modified by
the emergence of new electronic charge or spin order.
