Emergence of Triplet Correlations in Superconductor/Half Metallic Nanojunctions with Spin Active Interfaces

TL;DR

This paper investigates how spin-flip scattering at interfaces induces triplet pairing correlations in superconductor/half-metallic ferromagnet junctions, revealing their spatial behavior, dependence on interface properties, and effects on local magnetization and density of states.

Contribution

It provides a self-consistent theoretical analysis of triplet correlations in SFS junctions with spin-active interfaces, especially in half-metallic ferromagnets, highlighting their spatial extent and influence on electronic properties.

Findings

Spin-flip scattering generates odd-in-time triplet correlations with m=±1.

Triplet correlations can penetrate deeply into the superconductor and ferromagnet.

Density of states exhibits subgap bound states influenced by junction parameters.

Abstract

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. We derive and solve self consistently 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. We study the general spatial behavior of these and of $m=0$ correlations as a function of position and of spin-flip strength, $H_{spin}$. We concentrate on the case where the ferromagnet is half-metallic. We find that 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