A MICROSCOPIC MODEL FOR THE INTRINSIC JOSEPHSON TUNNELING IN HIGH-T-CSUPERCONDUCTORS

A quantitative analysis of a microscopic model for the intrinsic Josep hson effect in high temperature superconductors based on interlayer tu nneling is presented both within a mean-field BCS evaluation and a num erically essentially exact Quantum Monte-Carlo study. The pairing corr elations in the CuO2-planes are modelled by a 2D Hubbard model with at tractive interaction, a model which accounts well for some of the obse rved features such as the short planar coherence length. The stack of Hubbard planes is arranged on a torus, which is threaded by a magnetic flux. The current perpendicular to the planes is calculated as a func tion of applied flux (i.e. the phase), and - after careful elimination of finite-size effects due to single-particle tunneling - found to di splay a sinusoidal field dependence in accordance with interlayer Jose phson tunneling. Studies of the temperature dependence of the supercur rent reveal at best a mild elevation of the Josephson transition tempe rature compared to the planar Kosterlitz-Thouless temperature. These a nd other results on the dependence of the model parameters are compare d with a standard BCS evaluation.