Spin-split conductance and subgap peak in ferromagnet/superconductor spin valve heterostructures

We consider the separate spin channel contributions to the charge conductance in superconducting/ferromagnetic spin valve F1/N/F2/S structures. We find that the up- and down-spin conductance contributions may have a very different behavior in the subgap bias region (i.e., there is a spin-split conductance). This leads to a subgap peak in the total conductance. This peak behavior, which can be prominent also in N/F/S systems, is strongly dependent, in a periodic way, on the thickness of the intermediate ferromagnetic layer. We study this phenomenon for the ballistic scattering regime using a numerical self consistent method, with additional insights gained from an approximate analytic calculation for an infinite N/F/S structure. We study also the angular dependence on the relative magnetization angle between F1 and F2 of both the spin-split and the total conductance. We do so for realistic material parameters, layer thicknesses, and interface quality values relevant to previous [Jara et al., Phys. Rev. B 89, 184502 (2014)PRBMDO1098-012110.1103/PhysRevB.89.184502] experimental studies on such devices. We also find that the spin-split conductance is highly dependent on the interfacial scattering in these devices, and we carefully include these effects for realistic systems. A strong valve effect is found for the angularly dependent subgap peak conductance that is largely independent on the scattering and may prove useful in actual realizations of a superconducting spin valve device.