Berlin 2018 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 13: Poster Session I
HL 13.23: Poster
Monday, March 12, 2018, 17:30–19:30, Poster B
Ultrafast Coulomb-induced intervalley coupling in monolayer WS2 — Robert Schmidt1, Gunnar Berghäuser2, •Robert Schneider1, Malte Selig3, Philipp Tonndorf1, Ermin Malic2, Andreas Knorr3, Steffen Michaelis de Vasconcellos1, and Rudolf Bratschitsch1 — 1Institute of Physics and Center for Nanotechnology, University of Münster, 48149 Münster, Germany — 2Department for Applied Physics, Chalmers University of Technology, SE-41296, Gothenburg, Sweden — 3Department for Theoretical Physics, Technical University Berlin, 10623 Berlin, Germany
Monolayers of semiconducting transition metal dichalcogenides are promising for information processing due to the presence of two valleys, which are located at the K and K’ point of the Brillouin zone and separately addressable by circularly polarized light of different helicity. We perform ultrafast, spectrally and polarization-resolved pump-probe measurements on single mechanically exfoliated WS2 monolayers to elucidate the underlying coupling between the two valleys. Together with microscopic theory, we demonstrate that the strong signal, which is observed in the unpumped valley, is due to Coulomb-induced intervalley coupling [1]. This interaction explains the different degree of valley polarization obtained with ultrafast pump-probe measurements compared to photoluminescence studies.
[1] R. Schmidt et al.,"Ultrafast Coulomb-induced intervalley coupling in atomically thin WS2", Nano Lett. 16, 2945-2950, (2016)