Spin and Current Variations in Josephson Junctions

TL;DR

This paper investigates how a single spin embedded in a Josephson junction exhibits unusual dynamics due to superconducting correlations, affecting the current and spin precession.

Contribution

It derives an effective non-local in time spin action using Keldysh formalism, revealing novel spin dynamics in superconducting Josephson junctions.

Findings

Unconventional spin precession caused by superconducting correlations

Current modulation linked to spin dynamics

Effective spin action is non-local in time

Abstract

We study the dynamics of a single spin embedded in the tunneling barrier between two superconductors. As a consequence of pair correlations in the superconducting state, the spin displays rich and unusual dynamics. To properly describe the time evolution of the spin we derive the effective Keldysh action for the spin. The superconducting correlations lead to an effective spin action, which is non-local in time, leading to unconventional precession. We further illustrate how the current is modulated by this novel spin dynamics.