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O: Fachverband Oberflächenphysik
O 22: 2D Materials II: Electronic Structure (joint session O/TT)
O 22.6: Talk
Tuesday, March 19, 2024, 12:00–12:15, MA 005
Ultrafast Hidden Spin Polarization Dynamics of Bright and Dark Excitons in 2H-WSe2 — •Mauro Fanciulli1,2, David Bresteau2, Jérome Gaudin3, Shuo Dong4, Romain Géneaux2, Thierry Ruchon2, Olivier Tcherbakoff2, Jan Minar5, Olivier Heckmann1,2, Maria Christine Richter1,2, Karol Hricovini1,2, and Samuel Beaulieu3 — 1LPMS, CY Cergy Paris Université, 95031 France — 2Université Paris-Saclay, CEA, CNRS, LIDYL, 91191 France — 3Université de Bordeaux - CNRS - CEA, CELIA, 33405 France — 4Beijing National Laboratory for Condensed Matter Physics, 100190 China — 5University of West Bohemia, 30100 Czech Republic
We performed spin-, time- and angle-resolved extreme ultraviolet photoemission spectroscopy of excitons prepared by photoexcitation of inversion-symmetric 2H-WSe2 with circularly polarized light.
The very short probing depth of XUV photoemission permits selective measurement of photoelectrons originating from the top-most WSe2 layer, allowing for direct measurement of hidden spin polarization of bright and momentum-forbidden dark excitons.
Our results reveal efficient chiroptical control of bright excitons' hidden spin polarization. Following optical photoexcitation, intervalley scattering between nonequivalent K-K' valleys leads to a decay of bright excitons' hidden spin polarization. Conversely, the ultrafast formation of momentum-forbidden dark excitons acts as a local spin polarization reservoir, which could be used for spin injection in van der Waals heterostructures involving multilayer transition metal dichalcogenides.
Keywords: TMDC; spin; dynamics; excitons; photoemission