Localized dipolar excitons as a probe of correlated electronic states in van der Waals heterotrilayers

Correlated electronic states are discovered in moiré heterostructures, such as twist transition metal dichalcogenides. Here, we fabricate gated WSe₂/MoSe₂/WSe₂ heterotrilayer and use photoluminescence spectroscopy to study correlated electron behavior. We observe non-jittering localized interlayer excitons with linewidths as sharp as 26 μeV, which can sensitively probe electric fields, either from graphite gates or electrostatically doped electrons in the trilayer, by their dipolar energy shift. When the trilayer is doped with electrons, the localized interlayer excitons first form moiré trions with ~7 meV binding energy. Upon further electron doping, exciton energy shows several reproducible red- and blue-shifts correlated between different excitons at different sample positions. An analysis of the energy shifts with respect to fractional fillings suggests that these shifts arise from the switching of long-range charge ordered states, which gives rise to reconfiguration of electrons in the moiré structure. Furthermore, the degree of circular polarization of the emission depends on the filling - becoming unpolarized in certain filling range and finally recovering at higher fillings. These results establish localized dipolar excitons as a sensitive probe for correlated electron physics in moiré materials.