Spin/valley pumping of resident electrons in WSe2 and WS2 monolayers

Cedric Robert (1) , Sangjun Park (2) , Fabian Cadiz (2) , Laurent Lombez (1) , Lei Ren (1) , Hans Tornatzky (1) , Alistair Rowe (2) , Daniel Paget (2) , Fausto Sirotti (2) , Min Yang (3) , Dinh van Tuan (3) , Takashi Taniguchi (4) , Bernhard Urbaszek (1) , Kenji Watanabe (5) , Thierry Amand (1) , Hanan Dery (3) , Xavier Marie (1, 6)

1 LPCNO - Laboratoire de physique et chimie des nano-objets
2 LPMC - Laboratoire de physique de la matière condensée
3 Department of Electrical and Computer Engineering
4 WPI-MANA - International Center for Materials Nanoarchitectonics
5 Research Center for Functional Materials
6 Department of Physics

Abstract Monolayers of transition metal dichalcogenides are ideal materials to control both spin and valley degrees of freedom either electrically or optically. Nevertheless, optical excitation mostly generates excitons species with inherently short lifetime and spin/valley relaxation time. Here we demonstrate a very efficient spin/valley optical pumping of resident electrons in n-doped WSe 2 and WS 2 monolayers. We observe that, using a continuous wave laser and appropriate doping and excitation densities, negative trion doublet lines exhibit circular polarization of opposite sign and the photoluminescence intensity of the triplet trion is more than four times larger with circular excitation than with linear excitation. We interpret our results as a consequence of a large dynamic polarization of resident electrons using circular light.

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Matière Condensée [cond-mat]

Cedric Robert, Sangjun Park, Fabian Cadiz, Laurent Lombez, Lei Ren, et al.. Spin/valley pumping of resident electrons in WSe2 and WS2 monolayers. Nature Communications, 2021, 12 (1), ⟨10.1038/s41467-021-25747-5⟩. ⟨hal-03410584⟩