A modified phase coherence model for the non-linear c-axis V-I characteristics of highly anisotropic, high temperature superconductors

A modified Ambegaokar-Halperin thermal-fluctuation model has been developed to describe the c-axis V-I characteristics and low-current ohmic resistance of highly anisotropic superconductors in a magnetic field parallel to the c-axis. The model assumes loss of phase coherence across the CuO-planes associated with the correlated motion of pancake vortices in the liquid state. The predicted V-I characteristics in the current-induced transition from the superconducting to the resistive state are in good agreement with measurements on a 2212-BSCCO single crystal as a function of temperature and field, provided the effect of the interlayer capacitance is taken into account. The measurements are consistent with a flux pancake correlation length within the CuO-planes varying as ζ₀/(T/T₀- 1)^v, where ζ₀ = 1.57 ± 0.08 μm and v = 0.50 ± 0.01. Our measurements imply a current-dependent interlayer resistance above and below T_c.