Spin pumping in YIG/s-wave superconductor hybrids*

When a spin current is injected into a superconductor (SC) from an adjacent ferromagnet (F), the efficiency of the spin diffusion will be affected by the opening of the superconducting gap and by spin relaxation mechanisms [1]. As a counterpart, the spin dynamics in the F will also change across the superconducting transition. The study of the magnetization dynamics of the F is thus a useful approach to investigate the spin diffusion in the SC [2]. Under these premises, we combined an s-wave SC with Y₃Fe₅O₁₂ in a bilayer and studied by ferromagnetic resonance experiments the effects of the superconducting gap on the spin pumping efficiency into the SC, driven by the non-equilibrium magnetization precession of the ferrimagnetic insulator. The magnetization relaxation characterized by the damping parameter is severely reduced below T_c due to the opening of the superconducting gap. We also analyzed the spin to charge conversion by ISHE in the SC. The results will be discussed in terms of the spin sinking properties of s-wave superconductors and diffusion in the SC of spin-polarized quasiparticles.

[1] F. S. Bergeret et al., Rev. Mod. Phys. 90, 41001 (2018)
[2] D. Sanchez-Manzano et al., ArXiv:2009.03196(2020)