Abstract
We directly monitor exciton propagation in freestanding and -supported monolayers through spatially and time-resolved microphotoluminescence under ambient conditions. We find a highly nonlinear behavior with characteristic, qualitative changes in the spatial profiles of the exciton emission and an effective diffusion coefficient increasing from 0.3 to more than , depending on the injected exciton density. Solving the diffusion equation while accounting for Auger recombination allows us to identify and quantitatively understand the main origin of the increase in the observed diffusion coefficient. At elevated excitation densities, the initial Gaussian distribution of the excitons evolves into long-lived halo shapes with -scale diameter, indicating additional memory effects in the exciton dynamics.
- Received 18 October 2017
- Revised 12 January 2018
DOI:https://doi.org/10.1103/PhysRevLett.120.207401
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