Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 33: Poster Tuesday: Ultrafast Processes 2
O 33.7: Poster
Dienstag, 6. September 2022, 11:00–13:00, P3
Dark Exciton Formation Dynamics in TMDC Monolayers — •Sarah Zajusch1, Lasse Münster1, Raul Perea-Causin1, Samuel Brem1, Katsumi Tanimura1, Jens Güdde1, Yaroslav Gerasimenko2, Rupert Huber2, Ermin Malic1, Ulrich Höfer1, and Robert Wallauer1 — 1Fachbereich Physik, Philipps-Universität Marburg, Germany — 2Fachbereich Physik, Universität Regensburg, Germany
Charge transfer processes in two-dimensional TMDCs are governed by the formation of excitons. The excitonic landscape comprises optically accessible bright excitons as well as momentum- and spin-forbidden dark states. Our experimental setup combines time-resolved momentum microscopy with probe energies in the XUV regime which provides direct access to k-resolved exciton dynamics within the whole Brillouin zone on an ultrafast time scale.
Although structural features are very similar for different semiconductor TMDC materials, slight variations in both electronic band ordering and excitonic binding energy can drastically modify the excited population dynamics. We present a comparison of exciton formation in the two extreme cases of WS2 and MoSe2 monolayers after valley-sensitive excitation with circular polarized light. On the one hand, in MoSe2 the bright KK-exciton is the energetically most favorable state. On the contrary, in WS2, we additionally observe the ultrafast formation of energetically lower dark KK’- and KΣ-excitons. The microscopic understanding of these processes is crucial with regard to interlayer exciton formation in TMDC heterostructures.