Spin-orbit interaction induced in graphene by transition metal dichalcogenides

Abstract

We report a systematic study on strong enhancement of spin-orbit interaction (SOI) in graphene induced by transition-metal dichalcogenides (TMDs). Low-temperature magnetotoransport measurements of graphene proximitized to different TMDs (monolayer and bulk WSe2,WS2, and monolayer MoS2) all exhibit weak antilocalization peaks, a signature of strong SOI induced in graphene. The amplitudes of the induced SOI are different for different materials and thickness, and we find that monolayer WSe2 and WS2 can induce much stronger SOI than bulk WSe2,WS2, and monolayer MoS2. The estimated spin-orbit (SO) scattering strength for graphene/monolayer WSe2 and graphene/monolayer WS2 reaches ∼10 meV, whereas for graphene/bulk WSe2, graphene/bulk WS2, and graphene/monolayer MoS2, it is around 1 meV or less. We also discuss the symmetry and type of the induced SOI in detail, especially focusing on the identification of intrinsic (Kane-Mele) and valley-Zeeman (VZ) SOI by determining the dominant spin relaxation mechanism. Our findings pave the way for realizing the quantum spin Hall (QSH) state in graphene.