Ultrafast Hidden Spin Polarization Dynamics of Bright and Dark Excitons in 2 H − WSe 2

Mauro Fanciulli (1, 2) , David Bresteau (3) , Jérôme Gaudin (4) , Shuo Dong (5) , Romain Géneaux (6) , Thierry Ruchon (6, 3) , Olivier Tcherbakoff (6) , Ján Minár (7) , Olivier Heckmann (1, 6) , Maria Christine Richter (6, 1) , Karol Hricovini (1, 6) , Samuel Beaulieu (4)

1 LPMS - Laboratoire de Physique des Matériaux et des Surfaces
2 Physikalisches Institut [Würzburg]
3 ATTO - Attophysique
4 CELIA - Centre d'Etudes Lasers Intenses et Applications
5 Beijing National Laboratory for Condensed Matter Physics
6 LIDYL - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)
7 University of West Bohemia [Plzeň ]

We performed spin-, time-and angle-resolved extreme ultraviolet photoemission spectroscopy of excitons prepared by photoexcitation of inversion-symmetric 2H-WSe 2 with circularly polarized light. The very short probing depth of XUV photoemission permits selective measurement of photoelectrons originating from the topmost WSe 2 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 0 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.

Mots clés: Editors' Suggestion; Editors' Suggestion

Domaines: Physique [physics]

Mauro Fanciulli, David Bresteau, Jérôme Gaudin, Shuo Dong, Romain Géneaux, et al.. Ultrafast Hidden Spin Polarization Dynamics of Bright and Dark Excitons in 2 H − WSe 2. Physical Review Letters, 2023, 131 (6), pp.066402. ⟨10.1103/PhysRevLett.131.066402⟩. ⟨hal-04239132⟩