Valley-polarized spin tunneling in monolayer transition-metal dichalcogenides/ferromagnet hybrids driven by spin pumping and the spin Seebeck effect

We present a microscopic theory for valley-polarized spin current at a Monolayer transition-metal dichalcogenides (TMDC) /ferromagnet insulator (FI) interface under a perpendicular magnetic field generated by two routes: (i) microwave spin pumping at ferromagnetic resonance and (ii) a cross-plane thermal gradient that drives the spin Seebeck effect. Interfacial exchange mediates spin-flip tunneling into the Landau-quantized conduction band of a monolayer TMDC in a perpendicular magnetic field. Because the n=0 Landau level appears only in the K valley, spin flips become valley selective, yielding a pure valley current from unequal spin currents in K and K′. In the valence band, valley selectivity is mainly caused by spin splitting. When the spin splitting is negligible, the n=0 Landau level appears only in the K' valley, creating a valley current opposite to that in the conduction band. We predict quantum oscillations of the valley current versus chemical potential and magnetic field, which are strongest in WSe2 and weaker in MoS2 under spin pumping driving. The same valley filter operates for thermal magnons, producing a Seebeck-driven valley spin signal. Our results link spin pumping and spin Seebeck physics to valleytronics and provide a clear quantum-oscillatory signature of valley-selective spin injection.