Enhancement of the Josephson current by magnetic field in superconducting tunnel structures with paramagnetic spacer

TL;DR

This paper predicts that in certain superconductor-paramagnet tunnel structures, applying a magnetic field can enhance the Josephson current by weakening the destructive effects of magnetic fields on Cooper pairs, with potential experimental realization.

Contribution

It introduces a novel effect where magnetic fields can increase the Josephson current in superconductor-paramagnet structures due to specific spin interactions.

Findings

Magnetic field can enhance the Josephson critical current in specific structures.

Conditions exist where magnetic effects weaken the destruction of Cooper pairs.

Potential for experimental observation of the predicted effect.

Abstract

The dc Josephson critical current of a (S/M)IS tunnel structure in a parallel magnetic field has been investigated (here S is a superconductor, S/M is the proximity coupled S and paramagnet M bilayer and I is an insulating barrier). We consider the case when, due to the Hund's rule, in the M metal the effective molecular interaction aligns spins of the conducting electrons antiparallel to localized spins of magnetic ions. It is predicted that for tunnel structures under consideration there are the conditions when the destructive action of the internal and the applied magnetic fields on Cooper pairs is weakened and the increase of the applied magnetic field causes the field-induced enhancement of the tunnel critical current. The experimental realization of this interesting effect of the interplay between superconductivity and magnetism is also discussed.