15.05.2026 Role of Nonequilibrium Populations in Dark-Exciton Formation

New article on ultrafast dark‑exciton dynamics in 2H‑MoS₂ published in Physical Review Letters

The dispersion relation of bright and dark excitons E(Q) relates the exciton’s energy with its center-of-mass momentum Q. During the formation and thermalization of dark excitons, excitons with different energy and center-of-mass momenta Q contribute to the dynamics. Combining ultrafast momentum microscopy in the groups of Reutzel and Mathias (Göttingen) with microscopic modelling from the Malic group, we quantitatively evaluate the related dynamics. On the example of homobilayer 2H-MoS2, we show how dark excitons are formed on the 85 fs timescale and subsequently thermalize on the 150 fs timescale. 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. The results are now published in Physical Review Letters.

DOI: 10.1103/w29j-z48v