Observation of Momentum Forbidden Dark Excitons
Madeo et al. have observed momentum-forbidden, dark excitons and their dynamics in atomically thin semiconductors.
Madeo et al. from the Okinawa Institute of Science and Technology have recently reported the successful observation of dark excitons in a single atomic layer of WSe2 and their dynamics in the prestigious Science journal. The so called bright and dark excitons could be observed as predicted in literature. Surprisingly, the contribution of the dark excitons in the excited-state distribution was dominating the results, a finding initially not expected. Using a state-of-the-art time resolved XUV-µ-ARPES with a suitable pump energy, the group around Michael Man could successfully investigate this challenging phenomena. Thanks to the ability of performing ARPES experiments from small spots in combination with PEEM imaging, many of the existing technological challenges could be overcome.