Prediction of superconducting transition temperatures of heterostructures based on the quasiparticle spectrum

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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.