Dresden 2020 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 27: 2D semiconductors and van der Waals heterostructures III (joint session HL/DS)
HL 27.6: Vortrag
Dienstag, 17. März 2020, 11:30–11:45, POT 81
Transient Valley Grating Spectroscopy on WSe2 — Julian Wagner, Henning Kuhn, •Robin Bernhardt, Jingyi Zhu, and Paul van Loosdrecht — Universität zu Köln, II. Physikalisches Institut, D-50937 Köln, Germany
The absence of space inversion symmetry combined with strong spin-orbit interactions and time-reversal in monolayer transition metal dichalcogenides lead to the emergence of a new quantum degree of freedom, the valley pseudospin. This valley degree of freedom can be manipulated making use of the selection rules for light matter interaction, i.e. one can for instance create pure pseudospin up or down states. These states, however, will decay due to intervalley scattering of the excitonic states involved. The mechanisms leading to intervalley scattering are currently intensely debated, partially due to the lack of experiments directly addressing this.
A direct technique to address the intervalley scattering is Transient Valley Grating Spectroscopy, which is a novel 4-wave mixing approach similar to spin grating techniques. Using this approach, we investigated the valley pseudospin dynamics in monolayer WSe2. This allows for a direct determination of the intervalley scattering rate. Its temperature dependence shows that the dominant valley depolarization process is optical-phonon mediated intervalley scattering.