Emergence of triplet correlations in superconductor/half-metallic nanojunctions with spin-active interfaces

We study triplet pairing correlations induced in an SFS trilayer (where F is a ferromagnet and S an ordinary s -wave superconductor) by spin-flip scattering at the interfaces, via the derivation and self-consistent solution of the appropriate Bogoliubov-de Gennes equations in the clean limit. We find that the spin-flip scattering generates m=±1 triplet correlations, odd in time and study the general spatial behavior of these and of m=0 correlations as a function of position and of spin-flip strength, Hspin, concentrating on the case where the ferromagnet is half-metallic. For certain values of Hspin, the triplet correlations pervade the magnetic layer and can penetrate deeply into the superconductor. The behavior we find depends very strongly on whether the singlet order parameter is in the 0 or π state, which must in turn be determined self-consistently. We also present results for the density of states (DOS) and for the local magnetization, which, due to spin-flip processes, is not in general aligned with the magnetization of the half-metal, and near the interfaces, rotates as a function of position and Hspin. The average DOS in both F and S is shown to exhibit various subgap bound states positioned at energies that depend strongly on the particular junction state and the spin-flip scattering strength.