AC Josephson Effect Induced by Spin Injection

TL;DR

This paper explores how pure spin currents can induce AC Josephson effects in superconductors, revealing new phenomena involving spin injection and collective modes.

Contribution

It introduces the concept of AC Josephson oscillations driven by spin injection in superconductors, a novel mechanism linking spin currents to superconducting phase dynamics.

Findings

Spin injection induces AC voltage oscillations via Josephson tunneling.

Quasiparticle counterflow results in zero net electric current.

Resonance occurs due to Carlson-Goldman collective modes.

Abstract

Pure spin currents can be injected and detected in conductors via ferromagnetic contacts. We consider the case when the conductors become superconducting. A DC pure spin current flowing in one superconducting wire towards another superconductor via a ferromagnet contact induces AC voltage oscillations caused by Josephson tunneling of condensate electrons. Quasiparticles simultaneously counterflow resulting in zero total electric current through the contact. The Josephson oscillations can be accompanied by Carlson-Goldman collective modes leading to a resonance in the voltage oscillation amplitude.