Giant Nonequilibrium Valley Control via Spin-Selective Hot-Carrier Transfer in an Antiferromagnetic van der Waals Stack.

Spin-selective hot-carrier transfer at interfaces between two-dimensional (2D) semiconductors and magnets offers a nonequilibrium route to manipulate spin and valley degrees of freedom. In van der Waals heterostructures, such transfer can be enabled by type-III band alignment together with magnetic-field-induced spin polarization of the bands in adjacent magnetic layers. Yet, continuous and robust valley control with high magnetic-field susceptibility remains challenging, particularly beyond binary switching in out-of-plane easy-axis magnets. Here we fabricate a CrSBr/WSe2/CrSBr heterostructure, where two semiconductor-magnet interfaces promote efficient hot-carrier transfer. Utilizing valley-resolved magneto-photoluminescence spectroscopy, we reveal a pronounced field-sign-asymmetric response and a magnetic-state-dependent evolution of emergent spectral features that track the spin configuration of multilayer CrSBr via spin-selective hot-carrier transfer. This mechanism enables giant, continuous tuning, and magnetic-state-dependent reversal of the degree of circular polarization (DoCP), reaching ∼ 40% for excitons and ∼ 80% for trion emission. Our results establish spin-polarized interlayer hot-carrier transfer as an efficient knob for engineering valley polarization and coherence in TMDs, and highlight antiferromagnet-based stacks as a versatile platform for magnetically programmable quantum optoelectronic functionalities.