Strong electron-hole symmetric Rashba spin-orbit coupling in graphene/monolayer transition metal dichalcogenide heterostructures

摘要

Despite its extremely weak intrinsic spin-orbit coupling (SOC), graphene hasbeen shown to acquire considerable SOC by proximity coupling with exfoliatedtransition metal dichalcogenides (TMDs). Here we demonstrate strong inducedRashba SOC in graphene that is proximity coupled to a monolayer TMD film, MoS2or WSe2, grown by chemical vapor deposition with drastically different Fermilevel positions. Graphene/TMD heterostructures are fabricated with apickup-transfer technique utilizing hexagonal boron nitride, which serves as aflat template to promote intimate contact and therefore a strong interfacialinteraction between TMD and graphene as evidenced by quenching of the TMDphotoluminescence. We observe strong induced graphene SOC that manifests itselfin a pronounced weak anti-localization (WAL) effect in the graphenemagnetoconductance. The spin relaxation rate extracted from the WAL analysisvaries linearly with the momentum scattering time and is independent of thecarrier type. This indicates a dominantly Dyakonov-Perel spin relaxationmechanism caused by the induced Rashba SOC. Our analysis yields a Rashba SOCenergy of ~1.5 meV in graphene/WSe2 and ~0.9 meV in graphene/MoS2,respectively. The nearly electron-hole symmetric nature of the induced RashbaSOC provides a clue to possible underlying SOC mechanisms.