Transport mechanisms in a microparticle conductor

Transport properties of the microparticle superconductor described in the companion paper are represented by a percolative network of Josephson-coupled particles. Microparticle composite wires that have the best critical currents have resistivity ratios >1, suggesting that metallic conduction dominates and coupling occurs via weak links. The experimental jcis proportional to 1/ρeff, where 1/ρeff is the effective normal resistivity, in a qualitative analogy to a published relation calculated for a 3D percolative superconductor. The upper limit to jcis estimated taking into account percolation and flux pinning. Using an approximate theory for a percolative network this upper limit is expected to be , where is the critical current density in a perfect lattice of dirty weak links.