Andreev current and subgap conductance of spin-valve SFF structures

arXiv:1208.4741The Andreev current and the subgap conductance in a superconductor/insulator/ferromagnet (SIF) structure in the presence of a small spin-splitting field show novel interesting features (Ozaeta et al. in Phys. Rev. B 86:060509(R), 2012). For example, the Andreev current at zero temperature can be enhanced by a spin-splitting field h, smaller than the superconducting gap Δ, as has been recently reported by the authors. Also at finite temperatures, the Andreev current has a peak for values of the spin-splitting field close to the superconducting gap, h≈Δ. Finally, the differential subgap conductance at low temperatures shows a peak at the bias voltage eV=h. In this paper, we investigate the Andreev current and the subgap conductance in SFF structures with arbitrary direction of magnetization of the F layers. We show that all the aforementioned features occur now at the value of the “effective field”, which is the field acting on the Cooper pairs in the multi-domain ferromagnetic region, averaged over the decay length of the superconducting condensate into a ferromagnet. We also briefly discuss the heat transport and electron cooling in the considered structures.This work was supported by the Spanish Ministry of Economy and Competition under Project FIS2011-28851-C02-02, the Basque Government under UPV/EHU Project IT-366-07, the “Topological Quantum Phenomena” (No. 22103002) KAKENHI on Innovative Areas, a Grant-in-Aid for Scientific Research (No. 22710096) from MEXT of Japan, and JSPS Institutional Program for Young Researcher Overseas Visits. The work of A.O. was supported by the CSIC and the European Social Fund under JAE-Predoc program.Peer Reviewe