THEORY OF DIAMAGNETISM IN GRANULAR SUPERCONDUCTORS

We study a highly disordered network of superconducting granules linked by weak Josephson junctions in a magnetic field and develop a mean field theory for this problem. The diamagnetic response to a slow 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 λg and critical current jc and find that both λg-1 and jc are nonzero but are strongly suppressed by frustration. © 1995 The American Physical Society.