Abstract
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.
Highlights
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 charge order
Bilayer graphene and transition metal dichalcogenide (TMD) heterostructures have emerged as fascinating new platforms to realize and probe exotic phases of quantum matter
We expect our static potential model to capture the essential physical processes provided that the first umklapp bands appear below the excitation gap of the electronic state
Summary
Bilayer graphene and transition metal dichalcogenide (TMD) heterostructures have emerged as fascinating new platforms to realize and probe exotic phases of quantum matter. In contrast to twisted bilayer graphene, TMD-based heterostructures allow for the use of resonant optical reflection spectroscopy to study the signatures of new electronic phases, such as correlated. We note that recent photoluminescence experiments allow for the characterization of a static excitonic moirepotential in twisted heterobilayers [15,16,17,18,19] This periodic potential is strong for interlayer excitons [20,21,22]: In structures where two different TMD monolayers are in direct contact, new interand intralayer excitonic resonances arising either from localization at high-symmetry stacking points or from umklapp processes are observed. In stark contrast to these earlier works, the periodic static moirepotential experienced by the excitons in our sample is weak as compared to the exciton linewidth due to the hBN barrier layer: As a consequence, we observe only a single intralayer exciton resonance in the absence of electron or hole doping
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