Proximity-driven source of highly spin-polarized ac current on the basis of superconductor/weak ferromagnet/superconductor voltage-biased Josephson junction

TL;DR

This paper proposes a theoretical method to generate highly spin-polarized ac currents using a superconductor/weak ferromagnet/superconductor junction, controlled by voltage and proximity effects, with potential for coherent spin current sources.

Contribution

It introduces a novel approach to produce highly spin-polarized ac currents via proximity effects in SFS junctions, including a method to achieve phase-controlled coherence.

Findings

The ac current is highly spin-polarized due to non-equilibrium proximity effects.

The frequency of the ac current is tunable by the applied voltage.

Coherent ac currents with phase control can be generated by coupling probe electrodes.

Abstract

We theoretically investigate an opportunity to implement a source of highly spin-polarized ac current on the basis of superconductor/weak ferromagnet/superconductor (SFS) voltage-biased junction in the regime of essential proximity effect and calculate the current flowing through the probe electrode tunnel coupled to the ferromagnetic interlayer region. It is shown that while the polarization of the dc current component is generally small in case of weak exchange field of the ferromagnet, there is an ac component of the current in the system. This ac current is highly spin-polarized and entirely originated from the non-equilibrium proximity effect in the interlayer. The frequency of the current is controlled by the voltage applied to SFS junction. We discuss a possibility to obtain a source of coherent ac currents with a certain phase shift between them by tunnel coupling two probe electrodes at different locations of the interlayer region.