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

A magnetic field modifies optical properties and provides valley splitting in a molybdenum disulfide (MoS) monolayer. Here we demonstrate a scalable approach to the epitaxial synthesis of MoS 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 MoS layer. The calculations also predict a 16 meV spin-splitting at the Γ̅ point and 8 meV K̅- valley asymmetry for an out-of-plane magnetization. These findings suggest control over optical transitions in MoS 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.