Using time-resolved Kerr rotation, we measure the spin/valley dynamics of resident electrons and holes in single charge-tunable monolayers of the archetypal transition-metal dichalcogenide (TMD) semiconductor WSe2. In the n-type regime, we observe long (70 ns) polarization relaxation of electrons that is sensitive to in-plane magnetic fields By, indicating spin relaxation. In marked contrast, extraordinarily long (2 microsecond) polarization relaxation of holes is revealed in the p-type regime, that is unaffected by By, directly confirming long-standing expectations of strong spin-valley locking of holes in the valence band of monolayer TMDs. Supported by continuous-wave Kerr spectroscopy and Hanle measurements, these studies provide a unified picture of carrier polarization dynamics in monolayer TMDs, which can guide design principles for future valleytronic devices.
@article{arxiv.1704.05448,
title = {Gate controlled spin-valley locking of resident carriers in WSe2 monolayers},
author = {P. Dey and Luyi Yang and C. Robert and G. Wang and B. Urbaszek and X. Marie and S. A. Crooker},
journal= {arXiv preprint arXiv:1704.05448},
year = {2017}
}