Description
Multi-dimensional coherent spectroscopy (MDCS) goes beyond standard linear-response probes and provides a powerful tool for investigating correlations between quasiparticles such as excitons (bound electron-hole pairs). Here we present a microscopic theory of MDCS that accounts for the delocalized nature of excitons in two-dimensional semiconductors. In contrast to the more phenomenological few-level approaches typically employed for modelling MDCS, our theory features mobile excitons with continuous momentum degrees of freedom. We find that the energy continuum associated with exciton momenta is crucial for producing interaction-induced decoherence, as well as capturing the interference between different exciton-polaron quasiparticles in the case of charge-doped semiconductors. The spectra we obtain show strong qualitative agreement with recent experiments on doped monolayer MoSe$_2$. Our model illustrates the central importance of phase-space filling effects in polaron-polaron interactions as well as the utility of a microscopic approach to modelling MDCS experiments more generally.
| I am the presenting author | Yes |
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