ELECTROMAGNETIC PROPERTIES OF STACKS OF SUPERCONDUCTING LAYERS

A system of superconducting layers, coupled solely by the electromagnetic field, is analyzed. Thermal fluctuations induce isolated vortices in individual layers, whose mutual interaction increases logarithmically with separation. In an applied field, the penetration depth is increased over that of individual layers by a factor proportional to the volume fraction of the superconductor. The stiffness of a vortex line under an inhomogeneous displacement in adjacent layers is analyzed. The interaction between vortex lines is enhanced near a free surface, making possible the existence of an ordered vortex lattice at the surface, while it may not exist in the bulk of the sample. © 1990 The American Physical Society.