Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 57: Focus Session: Many-body effects in two-dimensional materials
O 57.9: Talk
Wednesday, March 9, 2016, 12:45–13:00, H16
Ultrafast Coulomb-induced intervalley coupling in atomically thin WS2 — Robert Schmidt1, •Gunnar Berghäuser2, Malte Selig3, Philipp Tonndorf1, Ermin Malic2, Andreas Knorr3, Steffen Michaelis de Vasconcellos1, and Rudolf Bratschitsch1 — 1Institute of Physics and Center for Nanotechnology, University of Münser, Münster Germany — 2Chalmers University of Technology, Department of Physics, SE-412 96 Gothenburg, Sweden — 3Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
Monolayers of semiconducting transition metal dichalcogenides hold the promise for a new paradigm in electronics by exploiting the valley degree of freedom in addition to charge and spin. For these materials valley polarization can be conveniently initialized and read out by circularly polarized light. However, the underlying microscopic processes governing the valley polarization in these atomically thin equivalents of graphene are still not fully understood. Here, we present a theoretical study on the ultrafast time-resolved intervalley dynamics in monolayer WS2 [1]. Based on a microscopic theory, we reveal the many-particle mechanisms behind the observed spectral features. We show that Coulomb-induced intervalley coupling explains the immediate and prominent pump-probe signal in the unpumped valley as well as the seemingly low valley polarization degrees typically observed in pump-probe measurements if compared to photoluminescence studies.
[1] R. Schmidt et al, submitted (2015)