Title: Strong electron-hole symmetric Rashba spin-orbit coupling in graphene/monolayer transition metal dichalcogenide heterostructures,
Abstract: Despite its extremely weak intrinsic spin-orbit coupling (SOC), graphene has
been shown to acquire considerable SOC by proximity coupling with exfoliated
transition metal dichalcogenides (TMDs). Here we demonstrate strong induced
Rashba SOC in graphene that is proximity coupled to a monolayer TMD film, MoS2
or WSe2, grown by chemical vapor deposition with drastically different Fermi
level positions. Graphene/TMD heterostructures are fabricated with a
pickup-transfer technique utilizing hexagonal boron nitride, which serves as a
flat template to promote intimate contact and therefore a strong interfacial
interaction between TMD and graphene as evidenced by quenching of the TMD
photoluminescence. We observe strong induced graphene SOC that manifests itself
in a pronounced weak anti-localization (WAL) effect in the graphene
magnetoconductance. The spin relaxation rate extracted from the WAL analysis
varies linearly with the momentum scattering time and is independent of the
carrier type. This indicates a dominantly Dyakonov-Perel spin relaxation
mechanism caused by the induced Rashba SOC. Our analysis yields a Rashba SOC
energy of ~1.5 meV in graphene/WSe2 and ~0.9 meV in graphene/MoS2,
respectively. The nearly electron-hole symmetric nature of the induced Rashba
SOC provides a clue to possible underlying SOC mechanisms.