The twist degree of freedom provides a powerful new tool for engineering the electrical and optical properties of van der Waals heterostructures. Here, we show that the twist angle can be used to control the spin-valley properties of transition metal dichalcogenide bilayers by changing the momentum alignment of the valleys in the two layers. Specifically, we observe that the interlayer excitons in twisted WSe2/WSe2 bilayers exhibit a high (>60%) degree of circular polarization (DOCP) and long valley lifetimes (>40 ns) at zero electric and magnetic fields. The valley lifetime can be tuned by more than three orders of magnitude via electrostatic doping, enabling switching of the DOCP from ~80% in the n-doped regime to <5% in the p-doped regime. These results open up new avenues for tunable chiral light-matter interactions, enabling novel device schemes that exploit the valley degree of freedom.
@article{arxiv.1912.11306,
title = {Electrically tunable valley dynamics in twisted WSe$_2$/WSe$_2$ bilayers},
author = {Giovanni Scuri and Trond I. Andersen and You Zhou and Dominik S. Wild and Jiho Sung and Ryan J. Gelly and Damien Bérubé and Hoseok Heo and Linbo Shao and Andrew Y. Joe and Andrés M. Mier Valdivia and Takashi Taniguchi and Kenji Watanabe and Marko Lončar and Philip Kim and Mikhail D. Lukin and Hongkun Park},
journal= {arXiv preprint arXiv:1912.11306},
year = {2020}
}
Comments
31 pages, 4 figures in main text, 5 figures in supplemental materials