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 5867-5873

2D 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

More information

Latest update

2/29/2024