Non-equilibrium diffusion of dark excitons in atomically thin semiconductors.

Autor:	Rosati R; Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany. roberto.rosati@physik.uni-marburg.de., Wagner K; Department of Physics, University of Regensburg, Regensburg D-93053, Germany.; Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany., Brem S; Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany. roberto.rosati@physik.uni-marburg.de., Perea-Causín R; Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden., Ziegler JD; Department of Physics, University of Regensburg, Regensburg D-93053, Germany.; Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany., Zipfel J; Department of Physics, University of Regensburg, Regensburg D-93053, Germany.; Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA., Taniguchi T; International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan., Watanabe K; Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan., Chernikov A; Department of Physics, University of Regensburg, Regensburg D-93053, Germany.; Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany., Malic E; Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany. roberto.rosati@physik.uni-marburg.de.; Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden.
Jazyk:	angličtina
Zdroj:	Nanoscale [Nanoscale] 2021 Dec 13; Vol. 13 (47), pp. 19966-19972. Date of Electronic Publication: 2021 Dec 13.
DOI:	10.1039/d1nr06230a
Abstrakt:	Atomically thin semiconductors provide an excellent platform to study intriguing many-particle physics of tightly-bound excitons. In particular, the properties of tungsten-based transition metal dichalcogenides are determined by a complex manifold of bright and dark exciton states. While dark excitons are known to dominate the relaxation dynamics and low-temperature photoluminescence, their impact on the spatial propagation of excitons has remained elusive. In our joint theory-experiment study, we address this intriguing regime of dark state transport by resolving the spatio-temporal exciton dynamics in hBN-encapsulated WSe 2 monolayers after resonant excitation. We find clear evidence of an unconventional, time-dependent diffusion during the first tens of picoseconds, exhibiting strong deviation from the steady-state propagation. Dark exciton states are initially populated by phonon emission from the bright states, resulting in creation of hot (unequilibrated) excitons whose rapid expansion leads to a transient increase of the diffusion coefficient by more than one order of magnitude. These findings are relevant for both fundamental understanding of the spatio-temporal exciton dynamics in atomically thin materials as well as their technological application by enabling rapid diffusion.
Databáze:	MEDLINE
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