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 ${\lambda }_g$ and critical current $j_c$ and find that both ${\lambda }_g^{-1\mathrm{}}$ and $j_c$ are nonzero but are strongly suppressed by frustration.

• Received 23 May 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.3447