Critical temperature of superconducting bilayers: theory and experiment

TL;DR

This paper introduces a comprehensive model for the critical temperature of superconducting bilayers that accurately predicts Tc across various film thicknesses and interface resistivities, validated through experiments.

Contribution

A generalized, unrestricted model for Tc of superconducting bilayers is developed and experimentally verified, enhancing device design capabilities.

Findings

Excellent agreement between theory and experiment for Tc and energy gap.

Model applicable to a wide range of film thicknesses and interface resistivities.

Provides practical insights for superconducting device engineering.

Abstract

A generalized model for the critical temperature Tc of superconducting bilayers is presented, which is valid with no restrictions to film thicknesses, Tc of the layers and interface resistivity. The model is verified experimentally on a series of Nb-Al and Ta-Al bilayers with Nb, Ta layer thicknesses of 100 nm and Al layer thicknesses ranging from 5 nm to 200 nm. Excellent agreement between theory and experiment was found for the energy gap and the Tc of bilayers. The results are important for designing practical superconducting devices.