Role of interfaces in the proximity effect in anisotropic superconductors

Abstract

We report measurements of the critical temperature of YBa 2 Cu 3 O 7 -YBCu 3-x Co x O 7ϩ␦ superconductornormal-metal (S-N) bilayer films. Depending on the morphology of the S-N interface, the coupling between S and N layers can be turned on to depress the T c of S by tens of degrees, or turned down so the layers appear almost totally decoupled. This effect can be explained by the mechanism of quasiparticle transmission into an anisotropic superconductor.

Investigation of Surface Roughness Effect on Transition Edge Sensor Microcalorimeters Using Multilayer Readout Wiring

“…This hypothesis may be supported by theoretical and experimental studies in other groups [8][9][10]. Proximity effects depend on the penetration of electrons from the normal metal into the superconducting films.…”

Influence of quasi-layer-by-layer roughness on proximity effects in thin film superconducting/normal-metal junctions

“…Interface roughness can induce a considerable reduction of the critical transition temperature as long as the in-plane coherence lengths are signi®cantly larger than the one out-of-plane n i ) n c . Indeed, under these conditions, measurements of the critical temperature T c in slowly grown YBa 2 Cu 3 O 7 ±YBa 2 Cu 3Àx Co x O 7d bilayers [5] revealed a good agreement with the former roughness theory predictions in terms of Eq. (1) [6].…”

Enhancement of proximity effects due to random roughness at a superconductor/metal interface

“…[7], X-ray reflectivity [8][9][10][11] etc. Moreover, in the experiments by Polturak et al [4], for example, the AFM topography images would allow a direct measurement of the height-height correlation function and/or the rms roughness amplitude versus lateral scan size [7,12] yielding therefore the roughness parameters s, j, and H. Other techniques to observe directly the changes in the SN-interface structure during growth of a normal metal on a superconducting film might involve e.g. X-ray reflectivity [8][9][10][11].…”

“…anisotropic high-temperature Cu-oxide superconductors) [1][2][3][4]. The penetration of Cooper pairs from the superconductor into the metal and electrons from the normal metal into superconductor determines the proximity effects [1,2], which manifest themselves by reducing the critical temperature T c of a thin superconducting film covered by a thick normal metal film [1,2].…”

“…with the roughness exponent H being a measure of the degree of surface irregularity [7,13] [4,6], a o 0:3 nm; and rms roughness amplitude s 5 nm s p d: The relative reduction in critical temperature DT c =T c has a trivial dependence on the rms roughness amplitude s; namely DT c =T c G s 2 ; while any complex dependence will arise solely from the roughness exponent H and the in-plane correlation length j. Fig.…”