Seminarium "Coherence-Correlations-Complexity" (KFT, PWr)

13:15 środa, 13-06-18
Sala 320a bud. A-1, Politechnika Wrocławska

Correlation effects in superconducting quantum dot systems

dr Vladislav Pokorny

Institute of Physics, Czech Academy of Sciences, Prague

A single-level quantum dot connected to superconducting leads is an ideal system for studying the interplay between electronic correlations and the superconducting order. The proximity effect allows the Cooper pairs to leak into the quantum dot, opening a gap in the density of states and the Andreev reflections give rise to a set of discrete subgap states. Moreover, the presence of a third, metallic electrode populates the gap with finite density of states and gives control over the Kondo effect.

We use the single-impurity Anderson model coupled to BCS superconducting leads and, optionally, a third metallic lead to study the system. In order to solve this model, we use a self-consistent, second-order perturbation theory method and compare the results to numerical methods as the CT-HYB quantum Monte Carlo and the numerical renormalization group (NRG). The focus is on the behavior of the Andreev subgap states, the Josephson current and the zero-pi quantum phase transition. We show the limits of usability of the presented methods and the agreement of our calculations with available experimental results.

  1. M. Žonda, V. Pokorný, V. Janiš, and T. Novotný, Sci. Rep. 5, 8821 (2015).
  2. T. Domański, M. Žonda, V. Pokorný, G. Górski, V. Janiš, and T. Novotný, Phys. Rev. B 95, 045104 (2017).
  3. V. Pokorný and M. Žonda, Physica B 536, 488 (2018).

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