Fyzikální ústav Akademie věd ČR

Seminar Tuesday, 01/10/2013 15:00 - 16:00

Speakers: Vladislav Pokorný (Department of Condensed Matter Theory, Institute of physics, ASCR, Prague; department of condensed matter physics, MFF UK Prague)
Place: Na Slovance, přednáškový sál v přízemí
Presented in English
Organisers: Department of Condensed Matter Theory

Abstract: Hybrid superconductor - quantum dot systems like carbon nanotubes coupled to superconducting electrodes have attracted much attention in recent years. They provide an almost ideal system where the interplay between superconducting order and electronic correlations can be studied in a controlled way. Recent experiments provided us with a number of interesting results. One of them is the existence of Andreev bound states within the superconducting gap. Another interesting property is the so-called zero-pi transition describing the reversal of the sign of the Josephson current under certain conditions. Such systems can be modeled by a single-impurity Anderson model coupled to BCS superconducting leads. We use diagrammatic perturbation techniques in the Coulomb interaction to capture the relevant physical phenomena, particularly the effect of the Coulomb interaction on the Andreev bound states. Results of the Hartree-Fock approximation, second-order perturbation theory and the random phase approximation are presented.