Non-equilibrium diffusion of dark excitons in atomically thin semiconductors
Artikel i vetenskaplig tidskrift, 2021
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 WSe2 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.
Författare
Roberto Rosati
Philipps-Universität Marburg
Koloman Wagner
Technische Universität Dresden
Universität Regensburg
Samuel Brem
Philipps-Universität Marburg
Raul Perea Causin
Chalmers, Fysik, Kondenserad materie- och materialteori
Jonas D. Ziegler
Universität Regensburg
Technische Universität Dresden
Jonas Zipfel
Universität Regensburg
Lawrence Berkeley National Laboratory
Takashi Taniguchi
National Institute for Materials Science (NIMS)
Kenji Watanabe
National Institute for Materials Science (NIMS)
Alexey Chernikov
Technische Universität Dresden
Universität Regensburg
Ermin Malic
Philipps-Universität Marburg
Chalmers, Fysik, Kondenserad materie- och materialteori
Nanoscale
2040-3364 (ISSN)
Vol. 13 47 19966-19972Graphene Core Project 3 (Graphene Flagship)
Europeiska kommissionen (EU) (EC/H2020/881603), 2020-04-01 -- 2023-03-31.
Ämneskategorier
Atom- och molekylfysik och optik
Annan fysik
Den kondenserade materiens fysik
DOI
10.1039/d1nr06230a
PubMed
34821228