Dynamical exponents for the current-induced percolation transition in high-Tc superconductors.

Abstract

A detailed study of dissipation in weak link networks of high-{ital T}{sub {ital c}} superconductors has been performed. The model for dissipation has been elaborated assuming a general correspondence with the problems of inhomogeneous charge transport. The model treats the basic experimental ingredients, current-voltage ({ital I}-{ital V}) and current-differential resistance ({ital I}-{ital dV}/{ital dI}) characteristics, as a current-induced critical phenomenon. The validity of a simple relationship between non-Ohmic weak link network and Ohmic classical percolation networks has been proved, allowing a quantitative interpretation of {ital I}-{ital V} characteristics. These characteristics are primary determined by dynamical features of transport on percolation networks. The model focuses on both aspects of of the scaling-related power law, its dynamical exponent and its prefactor, and gives specific predictions for magnetic field and temperature dependencies. The experimental results are in full agreement with both predictions. In particular, the experimental values of dynamical scaling exponents ({ital t}=2, {ital s}=0.7) coincide with generally accepted literature values for three-dimensional systems. {copyright} {ital 1996 The American Physical Society.}