Effect of Paramagnetic Impurities on Josephson Currents through Junctions with Normal-Metal Barriers

Abstract

The present paper deals with a study of the effect of paramagnetic impurities on zero-bias Josephson currents through junctions with normal-metal barriers at $T=0\mathrm{}°$K. The ratio of the barrier supercurrent of the impure-SNS (superconductor-normal-metal-superconductor) junction to that of the pure-SNS junction is found to be equal to $1-\zeta$, where $\zeta$ is a measure of the impurity concentration. For $\zeta <1\mathrm{}$, the Josephson current is nonzero and decreases with increase of impurity concentration, but in the gapless region (${\omega }_g=0\mathrm{}$) when $\zeta >~1$, the current is zero for $\zeta =1\mathrm{}$ and then becomes negative for $\zeta >1\mathrm{}$. At $\zeta =0\mathrm{}$, the result is in exact agreement with that of Ishii for the pure case.