Dimensional effects in V/Cu superconducting superlattices

Abstract

The superconductor-normal-metal phase transitions in V/Cu superlattices have been studied in parallel and perpendicular magnetic fields. Two crossovers from three-dimensional to two-dimensional and from two-dimensional to three-dimensional have been observed in magnetoresistance R(H,T) and in dependencies of the fluctuating conductivity σ’(T) in a parallel magnetic field. The crossover in low magnetic field is caused by the fact that the superconducting coherence length ξS(T) becomes of the order of the superstructure period Λ. The crossover in high magnetic field is due to the competition of the normal-metal coherence length ξN and magnetic length LH. The experimental results are in good agreement with numerical solution of the Ginzburg-Landau equation for superconductor-normal-metal-superconductor (SNS) superlattices.