Magnetic Proximity Coupling of Quantum Emitters in WSe to van der Waals Ferromagnets.

The realization of on-chip quantum networks requires tunable quantum states to encode information carriers on them. We show that CrGeTe (CGT) as a van der Waals ferromagnet can enable magnetic proximity coupling to site-controlled quantum emitters in WSe, giving rise to ultrahigh exciton factors up to 20 ± 1. By comparing the same site-controlled quantum emitter before and after ferromagnetic proximity coupling, we also demonstrate a technique to directly measure the resulting magnetic exchange field (MEF) strength. Experimentally determined values of MEF up to 1.2 ± 0.2 meV in the saturation regime approach the theoretical limit of 2.1 meV that was determined from density functional theory calculations of the CGT/WSe heterostructure. Our work extends the on-chip control of magneto-optical properties of excitons via van der Waals heterostructures to solid-state quantum emitters.