Spontaneous spin-polarized currents in superconductor-ferromagnetic metal heterostructures

We study a simple microscopic model for thin, ferromagnetic, metallic layers on a semi-infinite bulk superconductor. We find that for certain values of the exchange spliting, on the ferromagnetic side, the ground states of such structures feature spontaneously induced spin-polarized currents. Using a mean-field theory, which is self-consistent with respect to the pairing amplitude $\chi ,$ spin polarization $\overrightarrow{m},$ and spontaneous current $j_s,$ we show that not only are there Andreev bound states in the ferromagnet, but when their energies $E_n$ are near zero they support spontaneous currents parallel to the ferromagnetic-superconducting interface. Moreover, we demonstrate that the spin polarization of these currents depends sensitively on the band filling.