Disorder effect on non-ohmic resistive state in model high-temperature superconductor

Abstract

Microscopic defects (twin boundaries, oxygen defects) are important for high-temperature superconductive properties even in single crystals. The current ( I) z. sbnd;voltage ( V) characteristics is calculated for two-dimensional (2D) intra-granular superconductor model with random defects of Josephson couplings. A non-ohmic power-law V ∝ I α is found where, notably, the exponent α seems logarithmically sensitive to defect fraction ( p): α ∝ ln( p o / p, as connected 2D vortex-antivortex excitation. This peculiar property qualitatively correlates with recent experiments on ion-irradiated Y-Ba-Cu-O.