Prediction of superconducting transition temperatures of heterostructures based on first principles

TL;DR

This paper uses first-principles density functional theory to predict the superconducting transition temperatures of heterostructures, accurately matching experimental results for Au/Nb(100) systems and providing predictions for other compounds.

Contribution

First material-specific first-principles calculations of superconductor-normal metal heterostructures, including critical temperature predictions based on quasiparticle spectra.

Findings

Momentum-dependent quasiparticle bands due to Andreev reflection.

Strong momentum dependence of the induced superconducting gap.

Good agreement between calculated and experimental critical temperatures.

Abstract

The prediction of material-specific properties of superconducting systems such as the electronic structure and the transition temperature is one of the major challenge in modern solid-state physics. In this paper we present the first material specific calculations of realistic superconductor -- normal metal heterostructures using density functional theory. In particular, we calculate the quasiparticle spectrum of different normal metal overlayers on a Nb(100) host. We find that the Andreev reflection leads to the formation of momentum dependent quasiparticle bands in the normal metal. As a consequence, the spectrum has a strongly momentum dependent induced gap. From the thickness dependence of the gap size we calculate the superconducting critical temperature of Au/Nb(100) heterostructures where we find very good agreement with experiments. Moreover, predictions are made for similar heterostructures of other compounds.