Physical Mechanisms of Reduction of Critical Current Density across Grain Boundaries in High - Tc Superconductors

The combined effects of dilatation stresses, stoichiometric and electric-charge inhomogeneities, dx 2 -y2 symmetry of the superconducting order parameter and the faceted microstructure of grain boundaries are theoretically examined here as those causing the experimentally observed (see, e.g., Dimos et al, Phys.Rev. B 41 (1990) 4038) reduction of the critical current density Jc across grain boundaries in high-Tc cuprates. The enhancement of Jc across high-quality twist and doped grain boundaries in high-Tc cuprates is briefly discussed.