Spatiotemporal imaging of low-energy excitations with exciton spectroscopy II: theory

The strong excitonic response in transition-metal dichalcogenides (TMDs) has been extensively used to probe many-body physics in TMD monolayers as well as their heterostructures. In this work, we show that the evolution of high-energy excitonic spectra allows to directly visualize the propagation of low-energy excitations in space and time. To demonstrate this, we measured exciton-polaron reflectivity in doped TMDs following the application of a THz pump pulse. The time-resolved spectra reveal plasmonic modes propagating through the sample. Under an out-of-plane magnetic field, the spectra exhibit oscillations at the cyclotron frequency, offering a direct visualization of Landau level population.

In this talk, we present the theoretical framework underlying these observations and discuss potential and limitations of exciton spectroscopy.