Interlayer coupling in high temperature superconductors

We consider the high temperature superconductors such as YBaCuO as a stack of planar superconductors. The interlayer Josephson coupling deduced from the perpendicular penetration depth is of order 108 A/cm2 for YBaCuO, and some evidence supports a similar conclusion in BiSrCaCuO. Comparison with resistivities of YBaCuO and BiSrCaCuO crystals indicates clean limit behavior for in-plane supercurrents but dirty limit behavior for perpendicular supercurrents. The much lower values of transport critical current density Jc reported so far are understood in terms of weak pinning for the interplanar vortices as they slide between the planes. © 1989.