Non-equilibrium effects in a Josephson junction coupled to a precessing spin

TL;DR

This paper theoretically investigates how a precessing classical spin influences the electronic states and currents in a Josephson junction, revealing spin-dependent effects and potential for spin characterization.

Contribution

It introduces a model of a Josephson junction with a precessing spin, showing how spin precession affects Andreev states and generates spin and charge currents.

Findings

Andreev states develop sidebands due to spin precession

Precession induces a non-equilibrium population of states

A time-dependent spin current with rotating polarization is generated

Abstract

We present a theoretical study of a Josephson junction consisting of two s-wave superconducting leads coupled over a classical spin. When an external magnetic field is applied, the classical spin will precess with the Larmor frequency. This magnetically active interface results in a time-dependent boundary condition with different tunneling amplitudes for spin-up and spin-down quasiparticles and where the precession produces spin-flip scattering processes. We show that as a result, the Andreev states develop sidebands and a non-equilibrium population which depend on the precession frequency and the angle between the classical spin and the external magnetic field. The Andreev states lead to a steady-state Josephson current whose current-phase relation could be used for characterizing the precessing spin. In addition to the charge transport, a magnetization current is also generated.This spin current is time-dependent and its polarization axis rotates with the same precession frequency as the classical spin.