We demonstrate clear weak anti-localization (WAL) effect arising from induced Rashba spin-orbit coupling (SOC) in WS2-covered single-layer and bilayer graphene devices. Contrary to the uncovered region of a shared single-layer graphene flake, WAL in WS2-covered graphene occurs over a wide range of carrier densities on both electron and hole sides. At high carrier densities, we estimate the Rashba SOC relaxation rate to be ∼0.2ps−1 and show that it can be tuned by transverse electric fields. In addition to the Rashba SOC, we also predict the existence of a `valley-Zeeman' SOC from first-principles calculations. The interplay between these two SOC's can open a non-topological but interesting gap in graphene; in particular, zigzag boundaries host four sub-gap edge states protected by time-reversal and crystalline symmetries. The graphene/WS2 system provides a possible platform for these novel edge states.
@article{arxiv.1607.04647,
title = {Tunable spin-orbit coupling and symmetry-protected edge states in graphene/WS$_2$},
author = {Bowen Yang and Min-Feng Tu and Jeongwoo Kim and Yong Wu and Hui Wang and Jason Alicea and Ruqian Wu and Marc Bockrath and Jing Shi},
journal= {arXiv preprint arXiv:1607.04647},
year = {2016}
}