Role of Nonequilibrium Populations in Dark-Exciton Formation
Artikel i vetenskaplig tidskrift, 2026
The optical excitation of a bright exciton may be followed by the formation of lower-energy dark states. In these formation and relaxation processes, nonequilibrium exciton and phonon populations play a dominant role but remain so far largely unexplored, as most states are inaccessible by regular spectroscopies. Here, on the example of homobilayer 2H-MoS2, we realize direct access to the full exciton relaxation cascade from experiment and theory. We find distinct changes in the time-, energy-, and in-plane momentum-resolved photoemission spectral function that can be explained only when considering the formation and subsequent thermalization of excitonic nonequilibrium occupation distributions. In agreement with microscopic many-particle calculations, we quantify the timescales for the formation of a nonequilibrium dark-excitonic occupation and its subsequent thermalization to 85 and 150 fs, respectively. Our results provide a previously inaccessible view of the complete exciton relaxation cascade, which is of importance for the future characterization of nonequilibrium excitonic phases and the efficient design of optoelectronic devices.
Författare
Paul Werner
Georg-August-Universität Göttingen
Wiebke Bennecke
Georg-August-Universität Göttingen
Jan Philipp Bange
Georg-August-Universität Göttingen
Giuseppe Meneghini
Philipps-Universität Marburg
David Schmitt
Georg-August-Universität Göttingen
Marco Merboldt
Georg-August-Universität Göttingen
Anna M. Seiler
Georg-August-Universität Göttingen
Abdul Aziz AlMutairi
University of Cambridge
King Fahd University of Petroleum and Minerals
Kenji Watanabe
National Institute for Materials Science (NIMS)
Takashi Taniguchi
National Institute for Materials Science (NIMS)
G. S.Matthijs Jansen
Georg-August-Universität Göttingen
Junde Liu
Georg-August-Universität Göttingen
Daniel Steil
Georg-August-Universität Göttingen
Stephan Hofmann
University of Cambridge
R. Thomas Weitz
Georg-August-Universität Göttingen
Ermin Malic
Chalmers, Fysik, Kondenserad materie- och materialteori
Philipps-Universität Marburg
Stefan Mathias
Georg-August-Universität Göttingen
Marcel Reutzel
Georg-August-Universität Göttingen
Philipps-Universität Marburg
Physical Review Letters
0031-9007 (ISSN) 1079-7114 (eISSN)
Vol. 136 18 186903Ämneskategorier (SSIF 2025)
Den kondenserade materiens fysik
Annan fysik
DOI
10.1103/w29j-z48v
PubMed
42172393