Magnetic Proximity Effects in MoSe₂/CrBr₃ van der Waals Heterostructures

2D van der Waals heterostructures comprising ferromagnetic and semiconductor materials represent a unique platform to explore the magnetic exchange interactions that can introduce an effective magnetism in non-magnetic semiconducting layers. These interfacial magnetic proximity effects include electronic wavefunction overlap, spin-dependent charge transfer, and band hybridization.  Here, in MoSe₂/CrBr₃ heterostructures, we employ magnetic circular dichroism (MCD) spectroscopy to observe valley Zeeman splitting of the monolayer MoSe₂ excitonic resonances due to magnetic proximity effects from the underlying CrBr₃. The effective exchange field, studied at both the A- and B-exciton resonances in MoSe₂, is on the order of a few tesla. Imaging experiments reveal the presence of magnetic domains in the ferromagnetic CrBr₃ layer.