Long-range proximity effect for opposite-spin pairs in S/F heterostructures under non-equilibrium quasiparticle distribution

TL;DR

This paper predicts a new long-range proximity effect in superconductor/ferromagnet heterostructures under non-equilibrium conditions, where opposite-spin pairs penetrate deeper due to tailored quasiparticle distributions, significantly enhancing Josephson current.

Contribution

It introduces a novel mechanism for long-range proximity effect driven by non-equilibrium quasiparticle distributions, involving only opposite-spin pairs in S/F heterostructures.

Findings

Significant increase in Josephson current under specific voltages.

Long-range penetration of opposite-spin pairs in ferromagnets.

Potential for controlling supercurrent via non-equilibrium conditions.

Abstract

By now it is known that in a singlet superconductor/ferromagnet (S/F) structure the superconducting correlations carried by opposite-spin pairs penetrate into the ferromagnet over a short distance of the order of magnetic coherence length. The long-range proximity effect (LRPE), taking place on the length scale of the normal metal coherence length, can only be maintained by equal-spin pairs, which can be generated by magnetic inhomogeneities in the system. In this work we have predicted a new type of LRPE, which can take place in S/F heterostructures under non-equilibrium conditions. The superconducting correlations in the F region are generated by opposite-spin Cooper pairs and equal-spin pairs are not involved. The possibility for an opposite-spin pair to penetrate into the ferromagnet over a large distance is provided by creation of the proper non-equilibrium quasiparticle distribution there. This leads to a sharp increase (up to a few orders of magnitude) of the critical Josephson current through a S/F/S junction at some values of the voltage controlling the nonequilibrium distribution in the F interlayer.