Dresden 2020 – scientific programme
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MA: Fachverband Magnetismus
MA 8: Ultrafast Electron Dynamics I: Surfaces and Interfaces (joint session O/MA)
MA 8.5: Talk
Monday, March 16, 2020, 11:30–11:45, TRE Phy
Electron transfer dynamics in MoS2 imaged by time-resolved momentum microscopy — •Lasse Münster1, Sarah Zajusch1, Katsumi Tanimura2, Jens Güdde1, Robert Wallauer1, and Ulrich Höfer1 — 1Fachbereich Physik, Philipps-Universität Marburg, Germany — 2Institute of Scientific and Industrial Research, Osaka University, Japan
We investigate the electron dynamics in the topmost layer of MoS2 after optical excitation above the A-exciton resonance by means of time- and angle-resolved two-photon photoemission with a high harmonic probe. High harmonic generation in krypton is used to produce an almost isolated 7th harmonic of the 400 nm driving laser pulses at a repetition rate of 200 kHz. This is combined with tunable pump pulses in the visible range for resonant excitation. The photoemitted electrons are detected by a momentum microscope with time of flight detection that covers the full photoemission horizon in a single measurement. With a high harmonic probe this results in the imaging of the entire first Brillouin zone in TMDCs.
We observe an instantaneous occupation of the conduction band after optical excitation at all K-points followed by an ultrafast transfer to the conduction band minima at Σ. For longer delays the excited electron distribution localizes at these high symmetry points which we attribute to electron cooling. The real-space imaging capability of the momentum microscope allows the restriction of such experiments to micrometer-size regions which opens up the possibility to observe momentum-resolved charge transfer in TMDC heterostructures.