Crossover from the “clean” limit to the “dirty” limit in a network of S-N-S weak links in Y3/4Lu1/4Ba2Cu3O7 + BaPb1−x SnxO3 (0≤x≤0.25) composites

Abstract

Composites with a network of “superconductor-normal metal-superconductor” (S-N-S) weak links are prepared from a Y3/4Lu1/4Ba2Cu3O7 high-temperature superconductor and BaPb1−x SnxO3 (0≤x≤0.25) metal oxides. It is found that an increase in the tin content x in the nonsuperconducting component of the composite leads to an increase in the electrical resistivity ρ and, hence, to a decrease in the mean free path l of charge carriers. The temperature dependences of the electrical resistivity ρ(T) and critical current j C (T) of the composites are analyzed in the framework of the de Gennes theory of S-N-S junctions. It is demonstrated that the network of weak links in the composites is characterized by a crossover from the “clean” limit (l≥L) to the “dirty” limit (l≤L) (where L is the effective thickness of N interlayers between high-temperature superconductor grains).