Effects of interlayer coupling on the magnetic and transport properties of superconducting multilayers and high-temperature superconductors

Abstract

The effect of interlayer coupling on the transport properties and dissipation in a magnetic field is reviewed for superconducting multilayers including highly-anisotropic high-temperature superconductors (MIS) . For the applied field parallel to the superconducting layers the absence of any Lorentz-force dependence of the dissipation leads to an explanation other than flux motion. This is consistent with a Lorentz-force-independent, intergranular Josephson junction dissipation which dominates flux motion because of the strong, intrinsic pinning of the insulating regions between layers. However, in superconducting multilayers the dissipation is seen to cross over from phase slips at Josephson junctions to depinning of vortices from the external field at high fields and temperatures. For fields perpendicular to the superconducting layers the much greater resistive broadening in HTS is due to dissipation by thermally-activated flux motion, consistent with a lack of intrinsic pinning. We show experimental evidence that the associated flux motion occurs as a result of a crossover from three dimensional (3D) vortex lines to 2D independent pancake-like vortices, residing in the Cu-O layers. This 3D to 2D crossover occurs after kBT exceeds the Josephson coupling energy.