Momentum-Resolved Observation of Exciton Formation Dynamics in Monolayer WS2
Journal article, 2021
The dynamics of momentum-dark exciton formation in transition metal dichalcogenides is difficult to measure experimentally, as many momentum-indirect exciton states are not accessible to optical interband spectroscopy. Here, we combine a tunable pump, high-harmonic probe laser source with a 3D momentum imaging technique to map photoemitted electrons from monolayer WS2. This provides momentum-, energy- and time-resolved access to excited states on an ultrafast time scale. The high temporal resolution of the setup allows us to trace the early-stage exciton dynamics on its intrinsic time scale and observe the formation of a momentum-forbidden dark Kς exciton a few tens of femtoseconds after optical excitation. By tuning the excitation energy, we manipulate the temporal evolution of the coherent excitonic polarization and observe its influence on the dark exciton formation. The experimental results are in excellent agreement with a fully microscopic theory, resolving the temporal and spectral dynamics of bright and dark excitons in WS2.
dark excitons
trARPES
exciton dynamics
exciton band structure
monolayers
transition metal dichalcogenides
Author
Robert Wallauer
Philipps University Marburg
Raul Perea Causin
Chalmers, Physics, Condensed Matter and Materials Theory
2D-Tech
Lasse Münster
Philipps University Marburg
Sarah Zajusch
Philipps University Marburg
Samuel Brem
Philipps University Marburg
Jens Güdde
Philipps University Marburg
Katsumi Tanimura
Osaka University
Kai Qiang Lin
University of Regensburg
R. Huber
University of Regensburg
Ermin Malic
Philipps University Marburg
2D-Tech
Chalmers, Physics, Condensed Matter and Materials Theory
Ulrich Höfer
Philipps University Marburg
Nano Letters
1530-6984 (ISSN) 1530-6992 (eISSN)
Vol. 21 13 5867-58732D material-based technology for industrial applications (2D-TECH)
GKN Aerospace Sweden (2D-tech), 2021-01-01 -- 2024-12-31.
VINNOVA (2019-00068), 2020-05-01 -- 2024-12-31.
Subject Categories
Atom and Molecular Physics and Optics
Other Physics Topics
Condensed Matter Physics
DOI
10.1021/acs.nanolett.1c01839
PubMed
34165994