Perturbation theory of a superconducting 0−π impurity quantum phase transition

0452001 - FZÚ 2016 RIV GB eng J - Journal Article
Žonda, M. - Pokorný, Vladislav - Janiš, Václav - Novotný, T.
Perturbation theory of a superconducting 0−π impurity quantum phase transition.
Scientific Reports. Roč. 5, Mar (2015), s. 8821. ISSN 2045-2322. E-ISSN 2045-2322
R&D Projects: GA ČR GCP204/11/J042
Institutional support: RVO:68378271
Keywords : quantum dot * superconductivity * Josephson current * quantum phase transition * perturbation expansion
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 5.228, year: 2015

A single-level quantum dot with Coulomb repulsion 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 Matsubara self-consistent perturbation expansion. We show that at zero temperature second order of the expansion in its spin-symmetric version yields a nearly perfect agreement with the numerically exact calculations for the position of the 0 − π phase boundary at which the Andreev bound states reach the Fermi energy as well as for the values of single-particle quantities in the 0-phase. We present results for phase diagrams, level occupation, induced local superconducting gap, Josephson current, and energy of the Andreev bound states with the precision surpassing any (semi)analytical approaches employed thus far.
Permanent Link: http://hdl.handle.net/11104/0253043