Microscopic theory of spin transport at an interface between a superconductor and a ferromagnetic insulator

T. Kato, Y. Ohnuma, M. Matsuo, J. Rech, T. Jonckheere, T. Martin

Published 2019-01-08Version 1

We theoretically investigate spin transport at an interface between a ferromagnetic insulator(FI) and a superconductor(SC). Considering a simple FI-SC interface model, we derive formulas of the spin current and spin-current noise induced by microwave irradiation (spin pumping) or temperature gradient (the spin Seebeck effect). We show how the superconducting coherence factor affects the temperature dependence of the spin current. We also calculate the spin-current noise in thermal equilibrium and in non-equilibrium states induced by the spin pumping, and compare them quantitatively for an yttrium-iron-garnet-NbN interface.