INTRINSIC PINNING IN HIGH-T(C) SUPERCONDUCTORS

A phenomenological lattice theory of Ginzburg-Landau type is presented in which the order parameter is defined on the points of a discrete l attice only. For a straight flux line perpendicular to the c-axis situ ated directly on and halfway between the CuO-double layers of YBa2Cu3O 7-delta, the order parameter near the vortex core is calculated. The t otal line energy at these two positions is evaluated for lattice param eters ranging from the continuum limit to very small values of the coh erence length. The position-dependent lattice-periodic part of the fre e energy, the so-called Peierls potential for a straight flux line, is determined. The critical current densities associated with this intri nsic pinning potential are found to have the same order of magnitude a s those measured in epitaxial films of YBa2Cu3O7-delta.