%0 Journal Article %1 D1NR06230A %A Rosati, Roberto %A Wagner, Koloman %A Brem, Samuel %A Perea-Causín, Raül %A Ziegler, Jonas D. %A Zipfel, Jonas %A Taniguchi, Takashi %A Watanabe, Kenji %A Chernikov, Alexey %A Malic, Ermin %D 2021 %I The Royal Society of Chemistry %J Nanoscale %K c %N 47 %P 19966-19972 %R 10.1039/D1NR06230A %T Non-equilibrium diffusion of dark excitons in atomically thin semiconductors %U http://dx.doi.org/10.1039/D1NR06230A %V 13 %X 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.

@article{D1NR06230A, abstract = {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.}, added-at = {2023-03-23T15:04:42.000+0100}, author = {Rosati, Roberto and Wagner, Koloman and Brem, Samuel and Perea-Causín, Raül and Ziegler, Jonas D. and Zipfel, Jonas and Taniguchi, Takashi and Watanabe, Kenji and Chernikov, Alexey and Malic, Ermin}, biburl = {https://www.bibsonomy.org/bibtex/2a21b3c5cb7fea0ece8d86939ef6a7375/ctqmat}, day = 16, description = {Non-equilibrium diffusion of dark excitons in atomically thin semiconductors - Nanoscale (RSC Publishing) DOI:10.1039/D1NR06230A}, doi = {10.1039/D1NR06230A}, interhash = {cfc44aa1e10d980dc4ca2f2e8c153fb1}, intrahash = {a21b3c5cb7fea0ece8d86939ef6a7375}, journal = {Nanoscale}, keywords = {c}, month = {11}, number = 47, pages = {19966-19972}, publisher = {The Royal Society of Chemistry}, timestamp = {2023-03-23T15:04:42.000+0100}, title = {Non-equilibrium diffusion of dark excitons in atomically thin semiconductors}, url = {http://dx.doi.org/10.1039/D1NR06230A}, volume = 13, year = 2021 }