Josephson current in unconventional superconductors through an Anderson impurity

TL;DR

This paper investigates how Josephson current in a system with an Anderson impurity and unconventional superconductors is influenced by surface bound states and Coulomb interactions, revealing conditions that switch junction behavior.

Contribution

It demonstrates the role of surface zero energy bound states and Coulomb interactions in controlling Josephson junction phases in unconventional superconductors.

Findings

Surface bound states drive Josephson current.

Coulomb interaction can switch junction from π to 0.

Effect is more pronounced in p-wave superconductors.

Abstract

Josephson current for a system consisting of an Anderson impurity weakly coupled to two unconventional superconductors is studied and shown to be driven by a surface zero energy (mid-gap) bound-state. The repulsive Coulomb interaction in the dot can turn a $\pi$ junction into a 0-junction. This effect is more pronounced in p-wave superconductors while in high-temperature superconductors with $d_{x^2-y^2}$ symmetry it can exit for rather large artificial centers at which tunneling occurs within a finite region.