Superconducting proximity effect in epitaxial Nb(110)/Au(111)/Nb(110) trilayers

TL;DR

This study investigates how the superconducting proximity effect varies in epitaxial Nb/Au/Nb trilayers, revealing oscillations in the order parameter and potential for π junctions based on Au layer thickness.

Contribution

It provides experimental evidence of order-parameter oscillations and phase sign change in epitaxial Nb/Au/Nb trilayers, advancing understanding of proximity effects in these heterostructures.

Findings

Critical current density varies non-monotonically with Au thickness.

Order-parameter oscillations are intrinsic to the proximity effect.

Potential for π junction formation at specific Au thicknesses.

Abstract

Single-domain, epitaxially-grown Nb(110)/Au(111)/Nb(110) trilayers are studied in order to elucidate the superconducting proximity effect in the Au(111) layer. The critical current density, superconducting coherence length, and superconducting transition temperature, all show a non-monotonic dependence on the thickness of the Au layer. The analysis of the experimental data reasonably argues that a form of order-parameter oscillation is intrinsic to the proximity-induced Cooper pairs in the Au layer. We find that relative phase of the superconducting order parameter in the two Nb(110) layers changes sign as a function of Au(111) layer thickness tAu, offering a route to achieving a {\pi} junction for 0.94 nm<tAu<1.88 nm.