Energy gap of proximity-effect-induced superconductivity in NbCu multilayers

Abstract The nuclear spin-lattice relaxation rate, T 1 −1 , for 63 Cu in zero field from 4.2K down to 0.3K, has been measured in a series of NbCu multilayers. A BCS-like temperature dependence of T 1 −1 followed gradually by A Korringa-law-like one at low temperatures, has been found. It has been confirmed that such behavior of T 1 −1 comes from the anisotropic energy gap in the Cu-layers.