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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session

TT 33.59: Poster

Mittwoch, 28. März 2012, 15:00–19:00, Poster B

Influence of finite superconducting gaps on the proximity effect in interacting quantum dots — •David Futterer¹, Jacek Swiebodzinski¹, Michele Governale², and Jürgen König¹ — ¹Theoretische Physik, Universität Duisburg Essen and CeNIDE, 47048 Duisburg, Germany — ²School of Chemical and Physical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, PO Box 600, Wellington, New Zealand

The tunnel coupling of superconductors to an interacting quantum dot leads to the formation of Andreev-bound states (ABS), which are the excitation energies of the proximized dot. In the limit of large superconducting gaps in the leads, Δ → ∞, the hybrid system of dot and superconductors can be described exactly by an effective Hamiltonian.

Since in real systems the superconducting gap is usually not a large quantity it is an interesting question whether the predictions of the Δ→ ∞ calculations still have significance for real systems with finite gaps. In order to investigate this question we perform two different calculations: first, a systematic 1/Δ expansion where we find that the occurring currents show only small changes but we find indications that a finite Δ renormalizes the ABSs. To quantify the last statement we perform a second calculation where we resum the coupling to the superconductors at arbitrary values for Δ neglecting vertex corrections.