Spatial evolution of cooperative Raman scattering

Abstract

We have compared the parallel (Hc211) and perpendicular (&) upper critical field of superconducting multilayers with strong and weak interlayer coupling (Pb/Cu, Pb/Ge). The temperature dependence of Hc21/ reflects the expected dimensionality of the multilayers and can be interpreted in terms of the Takahashi-Tachiki proximity coupling model. In contrast with the strongly coupled Pb/Cu multilayers, weakly coupled Pb/Ge multilayers exhibit a strong thickness dependence of Hc2i. The electronic diffusion coefficient in Pb/Ge, obtained from Hc21 data, is not in agreement with the value calculated from the normal state resistivity. The disagreement reflects the highly inhomogeneous nature of the weakly coupled Pb/Ge multilayers.