On the theory of diamagnetism in granular superconductors

TL;DR

This paper develops a mean field theory for the diamagnetic response of highly disordered granular superconductors, revealing strong suppression effects due to frustration in their magnetic properties.

Contribution

It introduces a mean field framework for understanding diamagnetism in disordered granular superconductors with weak Josephson links, highlighting the effects of frustration.

Findings

Effective penetration depth $bb_g$ is calculated.

Critical current $j_c$ is derived.

Both $bb_g^{-1}$ and $j_c$ are suppressed by frustration.

Abstract

We study a highly disordered network of superconducting granules linked by weak Josephson junctions in magnetic field and develop a mean field theory for this problem. The diamagnetic response to a slow {\it variations} of magnetic field is found to be analogous to the response of a type-II superconductor with extremely strong pinning. We calculate an effective penetration depth $\lambda_g$ and critical current $j_c$ and find that both $\lambda_g^{-1}$ and $j_c$ are non-zero but are strongly suppressed by frustration.