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Exciton Diffusion and Halo Effects in Monolayer Semiconductors.

Authors
  • Kulig, Marvin1
  • Zipfel, Jonas1
  • Nagler, Philipp1
  • Blanter, Sofia1
  • Schüller, Christian1
  • Korn, Tobias1
  • Paradiso, Nicola1
  • Glazov, Mikhail M2
  • Chernikov, Alexey1
  • 1 Department of Physics, University of Regensburg, Regensburg D-93053, Germany. , (Germany)
  • 2 Ioffe Institute, Saint Petersburg, Russian Federation. , (Russia)
Type
Published Article
Journal
Physical Review Letters
Publisher
American Physical Society
Publication Date
May 18, 2018
Volume
120
Issue
20
Pages
207401–207401
Identifiers
DOI: 10.1103/PhysRevLett.120.207401
PMID: 29864294
Source
Medline
License
Unknown

Abstract

We directly monitor exciton propagation in freestanding and SiO_{2}-supported WS_{2} 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 30 cm^{2}/s, 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 μm-scale diameter, indicating additional memory effects in the exciton dynamics.

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