University of Minnesota
School of Physics & Astronomy
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Oriol T. Valls

Emergence of Triplet Correlations in Superconductor/Half Metallic Nanojunctions with Spin Active Interfaces
K. Halterman and O.T. Valls, Phys. Rev. B 80, 104502 (2009)

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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 $m=\pm 1$ 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, $H_{spin}$, concentrating on the case where the ferromagnet is half-metallic. For certain values of $H_{spin}$, 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 $\pi$ 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 $H_{spin}$. 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.