PERCOLATION IN SUPERCONDUCTING CUPRATES: RESISTIVITY AND CRITICAL CURRENTS

Abstract

Weak links in metallic cuprates yield complicated percolative conduction networks enhancing the intrinsic resistivity ρⁱ(T) = αⁱT + ρⁱ_0L to: The time-, temperature-, B-field- and voltage-dependencies of the current in — and in the transition to — the superconducting state are analyzed. Evidence is presented for arrays of microbridges being "electrically" the planar defects. These microbridges are typical superconductor-normal-conductor-superconductor (S-N-S) junctions, where pair tunneling is reduced by factors 10–10³ as compared to single particle, normal tunneling. The reduced pair tunneling is due to normal conductors coating cuprates being related to O-disorder and the tetragonal phase, which also occur by radiation damage. The time and voltage dependence implies rapid flux motion or flux creep along the planar defects causing noise and rf residual losses.