Nonequilibrium transport through a spinful quantum dot with superconducting leads

We study the nonlinear cotunneling current through a spinful quantum dot contacted by two superconducting leads. Applying a general nonequilibrium Green function formalism to an effective Kondo model, we study the rich variation in the IV characteristics with varying asymmetry in the tunnel coupling...

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Bibliographic Details
Published inPhysical review letters Vol. 107; no. 25; p. 256802
Main Authors Andersen, B M, Flensberg, K, Koerting, V, Paaske, J
Format Journal Article
LanguageEnglish
Published United States 16.12.2011
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Summary:We study the nonlinear cotunneling current through a spinful quantum dot contacted by two superconducting leads. Applying a general nonequilibrium Green function formalism to an effective Kondo model, we study the rich variation in the IV characteristics with varying asymmetry in the tunnel coupling to source and drain electrodes. The current is found to be carried, respectively, by multiple Andreev reflections in the symmetric limit, and by spin-induced Yu-Shiba-Rusinov bound states in the strongly asymmetric limit. The interplay between these two mechanisms leads to qualitatively different IV characteristics in the crossover regime of intermediate symmetry, consistent with recent experimental observations of negative differential conductance and repositioned conductance peaks in subgap cotunneling spectroscopy.
ISSN:1079-7114
DOI:10.1103/PhysRevLett.107.256802