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

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  • H. Beyer, Kiel University
  • ,
  • G. Rohde, Kiel University
  • ,
  • A. Grubišić Čabo
  • ,
  • A. Stange, Kiel University
  • ,
  • T. Jacobsen, Kiel University
  • ,
  • L. Bignardi, Università degli Studi di Trieste, Elettra-Sincrotrone Trieste S.C.p.A.
  • ,
  • D. Lizzit, Elettra-Sincrotrone Trieste S.C.p.A.
  • ,
  • P. Lacovig, Elettra-Sincrotrone Trieste S.C.p.A.
  • ,
  • C. E. Sanders, Rutherford Appleton Laboratory
  • ,
  • S. Lizzit, Elettra-Sincrotrone Trieste S.C.p.A.
  • ,
  • K. Rossnagel, Kiel University, German Electron Synchrotron
  • ,
  • P. Hofmann
  • M. Bauer, Kiel University

We employ time- and angle-resolved photoemission spectroscopy to study the spin- and valley-selective photoexcitation and dynamics of free carriers at the K̄ and K̄′ 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.

Original languageEnglish
Article number236802
JournalPhysical Review Letters
Volume123
Issue23
Number of pages6
ISSN0031-9007
DOIs
Publication statusPublished - Dec 2019

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