Proximity orbital and spin-orbit effects of bilayer graphene on monolayer WSe2 are investigated from first-principles. We find that the built-in electric field induces an orbital band gap of about 10 meV in bilayer graphene. Remarkably, the proximity spin-orbit splitting for holes is two orders of magnitude---the spin-orbit splitting of the valence band at K is about 2 meV---more than for electrons. Effectively, holes experience spin-valley locking due to the strong proximity of the lower graphene layer to WSe2. However, applying an external transverse electric field of some 1 V/nm, countering the built-in field of the heterostructure, completely reverses this effect and allows, instead for holes, electrons to be spin-valley locked with 2 meV spin-orbit splitting. Such a behavior constitutes a highly efficient field-effect spin-orbit valve, making bilayer graphene on WSe2 a potential platform for a field-effect spin transistor.
@article{arxiv.1706.06149,
title = {Proximity effects in bilayer graphene on monolayer WSe$_2$: Field-effect spin-valley locking, spin-orbit valve, and spin transistor},
author = {Martin Gmitra and Jaroslav Fabian},
journal= {arXiv preprint arXiv:1706.06149},
year = {2017}
}