Modern electronic devices heavily rely on the accurate control of charge and spin of electrons. The emergence of controllable valley degree of freedom brings new possibilities and presents a promising prospect towards valleytronics. Recently, valley excitation selected by chiral optical pumping has been observed in monolayer MoS2. In this work, we report polarized photoluminescence (PL) measurements for monolayer MoSe2, another member of the family of transition-metal-dichalcogenides (MX2), and observe drastic difference from the outcomes of MoS2. In particular, we identify a valley polarization (VP) up to 70% for B exciton, while that for A exciton is less than 3%. Besides, we also find a small but finite negative VP for A- trion. These results reveal several new intra- and inter-valley scattering processes which significantly affect valley polarization, hence provide new insights into exciton physics in monolayer MX2 and possible valleytronic applications.
@article{arxiv.1503.08631,
title = {Anomalous valley polarization in monolayer MoSe2},
author = {Anmin Zhang and Jiahe Fan and Yusheng Li and Jianting Ji and Guihua Zhao and Tianlong Xia and Tengfei Yan and Xinhui Zhang and Wei Zhang and Xiaoqun Wang and Qingming Zhang},
journal= {arXiv preprint arXiv:1503.08631},
year = {2015}
}
Comments
19 pages including supplementary information, 4 figures, 30 references