Dresden 2020 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 74: Poster IIIA
HL 74.7: Poster
Thursday, March 19, 2020, 15:00–17:30, P2/2OG
Diffusion of dark excitons in monolayer WSe2 at cryogenic temperatures — •Koloman Wagner1, Jonas Zipfel1, Jonas D. Ziegler1, Edith Wietek1, Barbara Meisinger1, Takashi Taniguchi2, Kenji Watanabe2, and Alexey Chernikov1 — 1Department of Physics, University of Regensburg, Regensburg, Germany — 2National Institute for Materials Science, Tsukuba, Ibaraki, Japan
Exciton propagation is studied in hBN-encapsulated WSe2 at liquid helium temperature through spatially- and time-resolved photoluminescence microscopy. To monitor diffusion we detect signatures from phonon-assisted recombination of low-energy, inter-valley dark exciton states. At low excitation densities we find efficient diffusion that appears to be intrinsically limited by exciton scattering with linear acoustic phonons in WSe2. These observations highlight the negligible role of localization through residual disorder and support the assignment of the studied spectral features to originate from free exciton states. At higher densities we detect an effective increase of the diffusion coefficient with distinct signatures of bimolecular recombination, qualitatively similar to the observations at room temperature.