80% Valley Polarization of Free Carriers in Singly Oriented Single-Layer WS2 on Au(111)

We employ time- and angle-resolved photoemission spectroscopy to study the spin- and valley-selective photoexcitation and dynamics of free carriers at the ¯¯¯¯K and ¯¯¯¯K′ points in singly oriented single-layer WS2/Au(111). Our results reveal that in the valence band maximum an ultimate valley polar...

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Bibliographic Details
Published in:Physical review letters 2019-12, Vol.123 (23)
Main Authors: Beyer, H, Rohde, G, Čabo, A Grubišić, Stange, A, Jacobsen, T, Bignardi, L, Lizzit, D, Lacovig, P, Sanders, C E, Lizzit, S, Rossnagel, K, Hofmann, P, Bauer, M
Format: Article
Language:English
Subjects:
Circular polarization
Conduction bands
Depolarization
Free electrons
Photoelectric emission
Photoexcitation
Polarized light
Room temperature
Spin dynamics
Valence band
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Summary:We employ time- and angle-resolved photoemission spectroscopy to study the spin- and valley-selective photoexcitation and dynamics of free carriers at the ¯¯¯¯K and ¯¯¯¯K′ points in singly oriented single-layer WS2/Au(111). Our results reveal that in the valence band maximum an ultimate valley polarization of free holes of 84% can be achieved upon excitation with circularly polarized light at room temperature. Notably, we observe a significantly smaller valley polarization for the photoexcited free electrons in the conduction band minimum. Clear differences in the carrier dynamics between electrons and holes imply intervalley scattering processes into dark states being responsible for the efficient depolarization of the excited electron population.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.123.236802