Superconductivity-enhanced spin pumping: Role of Andreev resonances

We describe a simple hybrid superconductor-ferromagnetic-insulator structure manifesting spin-resolved Andreev bound states in which dynamic magnetization is employed to probe spin related physics. We show that, at low bias and below T-c, the transfer of spin angular momentum pumped by an externally driven ferromagnetic insulator is greatly affected by the formation of spin-resolved Andreev bound states. Our results indicate that these bound states capture the essential physics of condensate-facilitated spin flow. For finite thicknesses of the superconducting layer, comparable to the coherence length, resonant Andreev bound states render highly transmitting subgap spin transport channels. We point out that the resonant enhancement of the subgap transport channels establishes a prototype Fabry-Perot resonator for spin pumping.

Automated summary

We investigate spin-resolved Andreev bound states in a hybrid superconductor-ferromagnetic-insulator structure. The transfer of spin angular momentum by an externally driven ferromagnetic insulator is greatly affected by the formation of these bound states at low bias and below the critical temperature. Resonant Andreev bound states in superconducting layer of finite thickness establish highly transmitting subgap spin transport channels, forming a prototype Fabry-Perot resonator for spin pumping.