Regensburg 2019 – scientific programme
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O: Fachverband Oberflächenphysik
O 80: Ultrafast Electron Dynamics at Surfaces and Interfaces I
O 80.3: Talk
Thursday, April 4, 2019, 11:00–11:15, H16
Valley-polarized excitation in singly-oriented monolayer WS2/Au(111) — •Hauke Beyer1, Gerald Rohde1, Antonija Grubisic Cabo2, Ankatrin Stange1, Luca Bignardi3, Daniel Lizzit3, Paolo Lacovig3, Silvano Lizzit3, Kai Rossnagel1, Philip Hofmann2, and Michael Bauer1 — 1IEAP, Kiel University, Germany — 2Department of Physics and Astronomy, Aarhus University, Denmark — 3Elettra Sincrotrone Trieste, Italy
Time- and angle-resolved photoelectron spectroscopy (trARPES) is employed to study the valley-selective excitation and near-surface dynamics of carriers in singly-oriented monolayer WS2/Au(111). Upon photoexcitation with circularly polarized light (λ ≈ 590 nm), we observe a selective population of both valence and conduction band at K and K′, respectively.
Our results are consistent with the fraction of domains with mirror orientation being ≤10 % , a value that was determined in diffraction experiments [1].
The quantitative analysis of the data indicates a valley polarization in the valence band of ≈ 90 % , while in the conduction band the valley polarization only reaches values of ≈ 70 % .
We explain this difference by the small spin-orbit splitting of the conduction band, which promotes intervalley scattering processes.
Different carrier dynamics of valence and conduction band population further hint to intervalley scattering being of relevance for the depolarization of the conduction band.
[1] Luca Bignardi et al., arXiv:1806.04928v2