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Dresden 2020 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 22: 2D Materials and their Heterostructures I (joint session DS/HL/O)

HL 22.7: Vortrag

Dienstag, 17. März 2020, 11:00–11:15, CHE 89

Unveiling valley lifetimes of free charge carriers in monolayer WSe2 — •Manfred Ersfeld1, Frank Volmer1, Lars Rathmann1, Luca Kotewitz1, Maximilian Heithoff1, Mark Lohmann2, Bowen Yang3, Kenji Watanabe4, Takashi Taniguchi4, Ludwig Bartels3, Jing Shi2, Christoph Stampfer1, 5, and Bernd Beschoten112nd Institute of Physics and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany — 2Department of Physics and Astronomy, University of California, Riverside, California 92521, USA — 3Department of Chemistry and Materials Science & Engineering Program, University of California, Riverside, California 92521, USA — 4National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan — 5Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany

We report on nanosecond long, gate-dependent valley lifetimes of free charge carriers in WSe2, unambiguously identified by the combination of time-resolved Kerr rotation (TRKR) and electrical transport measurements. While the valley polarization increases when tuning the Fermi level into the conduction or valence band, there is a strong decrease of the respective valley lifetime consistent with both electron-phonon and spin-orbit scattering. The longest lifetimes are seen for spin-polarized bound excitons in the band gap region. We explain our findings via two distinct, Fermi level-dependent scattering channels of optically excited, valley polarized bright trions either via dark or bound states.

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