Severe discrepancies between experiment and theory in the superconducting proximity effect

TL;DR

This study examines the superconducting proximity effect in SN double layers, revealing significant discrepancies between experimental results and theoretical predictions across different materials, especially in the thin film regime.

Contribution

It provides a detailed comparison of experimental data with a recent numerical simulation, highlighting material-dependent deviations in the proximity effect.

Findings

Large discrepancies for Cu, Ag, Au, Mg layers

Reduced discrepancies for Cd, Zn, Al layers

Good agreement for In, Sn layers

Abstract

The superconducting proximity effect is investigated for SN double layers in a regime where the resulting transition temperature T_{c} does not depend on the mean free paths of the films and, within limits, not on the transparency of the interface. This regime includes the thin film limit and the normalized initial slope S_{sn}= (d_{s}/T_{s})|dT_{c}/dd_{n}|. The experimental results for T_{c} are compared with a numerical simulation which was recently developed in our group. The results for the SN double layers can be devided into three groups: (i) When N = Cu, Ag, Au, Mg a disagreement between experiment and theory by a factor of the order of three is observed, (ii) When N = Cd, Zn, Al the disagreement between experiment and theory is reduced to a factor of about 1.5, (iii) When N = In, Sn a reasonably good agreement between experiment and theory is observed.