Direct Spectroscopic Evidence of Magnetic Proximity Effect in MoS₂ Monolayer on Graphene/Co

A magnetic field modifies optical properties and provides valley splitting in a molybdenum disulfide (MoS₂) monolayer. Here we demonstrate a scalable approach to the epitaxial synthesis of MoS₂ monolayer on a magnetic graphene/Co system. Using spin- and angle-resolved photoemission spectroscopy we observe a magnetic proximity effect that causes a 20 meV spin-splitting at the Γ̅ point and canting of spins at the K̅ point in the valence band toward the in-plane direction of cobalt magnetization. Our density functional theory calculations reveal that the in-plane spin component at K̅ is localized on Co atoms in the valence band, while in the conduction band it is localized on the MoS₂ layer. The calculations also predict a 16 meV spin-splitting at the Γ̅ point and 8 meV K̅-K′̅ valley asymmetry for an out-of-plane magnetization. These findings suggest control over optical transitions in MoS₂ via Co magnetization. Our estimations show that the magnetic proximity effect is equivalent to the action of the magnetic field as large as 100 T.