Magnetic-field dependence of conductance in microjunctions employing nonhomogeneous superconducting electrodes.

Abstract

Zero bias anomaly phenomena in conductance spectra relative to superconductor/normal metal--constriction--normal metal (${\mathit{S}}_{1}$/${\mathit{N}}_{1}$-c-${\mathit{N}}_{2}$) junctions are interpreted in terms of the proximity effect. Attention is focused in particular on the influence of the magnetic field on the conductance in point contact junctions and microjunctions with nonhomogeneous base electrodes (${\mathit{S}}_{1}$/${\mathit{N}}_{1}$). We find that the highly transmissive nature of the ${\mathit{N}}_{1}$-c-${\mathit{N}}_{2}$ interface is fundamental in determining the weak dependence of zero bias conductance on the applied magnetic field. The predictions of our model are compared with experimental data on Nb based junctions by Xiong et al. [Phys. Rev. Lett. 71, 1907 (1993)], supplying helpful information on the actual morphology of the structures. \textcopyright{} 1996 The American Physical Society.