THE EFFECT OF STRONG FLUX LINE CORRELATIONS ON THE IRREVERSIBILITY LINE OF HIGH-TEMPERATURE SUPERCONDUCTORS

A phenomenological model is proposed to account for a recently observed crossover in the temperature dependence of the irreversibility line of high temperature superconductors from a (1-T/T(c))3/2 to a (1-T/T(c))3 dependence. The model, which distinguishes between weak correlations and strong correlations in the flux line lattice, indicates that the crossover should occur at magnetic fields corresponding to a flux line spacing of about lambda/4, lambda being the penetration depth transverse to the field.