14.05.2025 Pre-print advertisement: "The role of non-equilibrium populations in dark exciton formation"

In 2D semiconductors, following the excitation of bright excitons, many-particle scattering can lead to the formation of lower-energy dark excitonic states. Importantly, the initial population in these dark states may be in a non-equilibrium condition and subsequent scattering events are necessary for the thermalization of the excitonic distribution.

In our new pre-print, we experimentally study the non-equilibrium excitonic distribution in bright and dark states using femtosecond momentum microscopy. In full agreement with microscopic modelling, we quantify the timescales for dark exciton formation and thermalization to 85 fs and 150 fs, respectively. Our results provide a previously inaccessible view on the complete exciton relaxation cascade, which is of importance for the future characterization of non-equilibrium excitonic phases and the efficient design of optoelectronic devices based on two-dimensional materials.

Thanks to the teams around Stephan Hofmann (University of Cambridge), Thomas Weitz (Georg-August-Universität Göttingen), Ermin Malic (Philipps-Universität Marburg), and Stefan Mathias (Georg-August-Universität Göttingen). Special thanks to the key players: Paul Werner, Wiebke Bennecke, Jan Philipp Bange and Giuseppe Meneghini.

Publication:

P. Werner, W. Bennecke, J. P. Bange, G. Meneghini, D. Schmitt, M. Merboldt, A. M. Seiler, A. A. AlMutairi, K. Watanabe, T. Taniguchi, G. S. M. Jansen, J. Liu, D. Steil, S. Hofmann, R. T. Weitz, E. Malic, S. Mathias, M. Reutzel, The role of non-equilibrium populations in dark exciton formation, arXiv:2505.06074 (2025).