Novel Spin Dynamics in a Josephson Junction

TL;DR

This paper investigates the unusual dynamics of a single spin in a Josephson junction, revealing non-local effects and unconventional precessions caused by superconducting correlations, with potential experimental implications.

Contribution

It introduces a generalized effective action for the spin in a superconducting junction, incorporating non-local time effects due to pair correlations.

Findings

Unconventional spin precession dynamics observed

Effective spin action includes non-local in time terms

Predictions applicable to macroscopic spin clusters

Abstract

We address 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 a rich and unusual dynamics. To properly describe the time evolution of the spin we find the generalized Wess-Zumino-Witten-Novikov term in the effective action for the spin on the Keldysh contour. The superconducting correlations lead to an effective spin action which is non-local in time leading to unconventional precessions. Our predictions might be directly tested for macroscopic spin clusters.