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Published September 2016 | Submitted
Journal Article Open

Tunable spin–orbit coupling and symmetry-protected edge states in graphene/WS_2


We demonstrate clear weak anti-localization (WAL) effect arising from induced Rashba spin–orbit coupling (SOC) in WS_2-covered single-layer and bilayer graphene devices. Contrary to the uncovered region of a shared single-layer graphene flake, WAL in WS_2-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 ~0.2 ps^(-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/WS_2 system provides a possible platform for these novel edge states.

Additional Information

© 2016 IOP Publishing. Received 15 July 2016; Accepted 30 August 2016; Published 13 September 2016. We gratefully acknowledge Roger Mong for valuable discussions. This work was supported by the DOE BES award No. DE-FG02-07ER46351 (BY and JS) and award No. DE-FG02-05ER46237 (JW and RW); NSF through grant DMR-1341822 (MT and JA); the Caltech Institute for Quantum Information and Matter, an NSF Physics Frontiers Center with support of the Gordon and Betty Moore Foundation; and the Walter Burke Institute for Theoretical Physics at Caltech. DFT simulations were performed on the U.S. Department of Energy Supercomputer Facility (NERSC).

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Submitted - 1607.04647v1.pdf


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October 20, 2023