Modulation of Exciton-Phonon Coupling at Correlated Insulating State of Moiré Superlattice

Moiré superlattice of van der Waals materials present an emergent paradigm to study correlated physics, such as the many-body interactions between photons, excitons and phonons. Exciton-phonon coupling (EPC) plays a crucial role in various physical processes, such as optical absorption and photoluminescence, valley scattering, electrical and thermal transport. Exploring the behaviors of EPC at correlated phases may provide insights into the formation mechanism of insulating states and their electrical and thermal transport behaviors. However, the modulation of EPC in moiré superlattice has not been explored in detail till now, especially the behaviors of different kinds of EPCs (Deformation potential, DP and Fröhlich interaction, FI). EPC can be involved in the resonant Raman scattering, and it has been demonstrated that the intralayer excitons can well couple with the phonons in transition metal dichalcogenides. Here we use excitonic resonant Raman spectra to study the EPC in MoS₂/WSe₂ moiré superlattice. The component of DP and FI can be separated in circularly polarized configuration. We found that both DP- and FI-determined Raman intensities are enhanced at Mott insulating state. However, Raman intensity determined by FI is affected more obviously than DP, that is, FI is much more sensitive to the formation of correlated phases. This conclusion is further supported by the temperature dependence of DP and FI. FI determined Raman intensity decreases much faster than DP with the increase of temperature. This work demonstrates that correlated electronic lattice provides a prototype for further studying and modulating the many-body states.