Momentum-Resolved Observation of Exciton Formation Dynamics in Monolayer WS2
Artikel i vetenskaplig tidskrift, 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


exciton dynamics

exciton band structure


transition metal dichalcogenides


Robert Wallauer

Philipps-Universität Marburg

Raul Perea Causin

Chalmers, Fysik, Kondenserad materie- och materialteori


Lasse Münster

Philipps-Universität Marburg

Sarah Zajusch

Philipps-Universität Marburg

Samuel Brem

Philipps-Universität Marburg

Jens Güdde

Philipps-Universität Marburg

Katsumi Tanimura

Osaka University

Kai Qiang Lin

Universität Regensburg

R. Huber

Universität Regensburg

Ermin Malic

Philipps-Universität Marburg


Chalmers, Fysik, Kondenserad materie- och materialteori

Ulrich Höfer

Philipps-Universität Marburg

Nano Letters

1530-6984 (ISSN) 1530-6992 (eISSN)

Vol. 21 13 5867-5873

2D material-baserad teknologi för industriella applikationer (2D-TECH)

GKN Aerospace Sweden (2D-tech), 2021-01-01 -- 2024-12-31.

VINNOVA (2019-00068), 2020-05-01 -- 2024-12-31.


Atom- och molekylfysik och optik

Annan fysik

Den kondenserade materiens fysik





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