Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 19: Superconductivity: Poster Session

TT 19.38: Poster

Montag, 7. März 2016, 15:00–18:00, Poster D

Perturbation theory for a single-level quantum dot connected to superconducting leads — •Vladislav Pokorný¹, Martin Žonda², Václav Janiš¹, and Tomáš Novotný² — ¹Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Praha, Czech Republic — ²Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 12116 Praha, Czech Republic

The zero-pi quantum phase transition in a single-level quantum dot attached to two superconducting leads is studied via the perturbation expansion in the interaction strength. We use the Nambu formalism and the standard many-body diagrammatic representation of the impurity Green functions to formulate the self-consistent perturbation expansion. We show that at zero temperature second order of the expansion in its spin-symmetric version yields a good agreement with the numerical renormalization group calculations for the position of the phase boundary as well as for the parameters in the zero phase. We present results for phase diagrams, level occupation, induced local superconducting gap, Josephson current and energy of the Andreev bound states. We also show the agreement of the second order perturbation method with the existing experimental data.