Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, CZ-12116 Praha 2, Czech Republic

报告摘要：

I will present a brief overview of relatively simple theoretical approaches developed in our Prague group in past several years and applied to the problem of description of correlated quantum dots attached to the BCS superconducting leads. As a thorough Quantum Monte Carlo analysis of the experimental data showed realistic experimental setups can be even quantitatively captured by the Single Impurity Anderson Model (SIAM) with superconducting leads which is thus in the focus of our studies. We have shown that self-consistent perturbation expansion up to the second order in the interaction strength yields at zero temperature and for a wide range of other parameters excellent results for the position of the 0 - π impurity quantum phase transition boundary and the Josephson current as well as the energy of Andreev bound states in the 0-phase. This method can be also extended to the three-terminal situation with an extra normal lead corresponding to the experimentally interesting STM setup, where it allows to study phase-dependent Kondo physics.

Furthermore, we have discovered exact identities connecting symmetric and asymmetric coupling situations which significantly reduce computational requirements in experimentally generic asymmetric setups and provided simple approximate analytical formulas for the fitting of the phase boundaries from finite-temperature experimental data. I will also briefly mention an exact mapping of a half-filled superconducting SIAM onto a normal SIAM with a structured semiconducting lead which significantly simplifies some technical aspects of its NRG solution and a simple way of determination of the quantum critical point from finite-temperature QMC statistics. Finally, the most recent extensions of those methods to more quantum dots or superconducting leads will be mentioned.

报告人简介：

Assoc. Prof. Tomáš Novotný is a condensed matter theorist (Ph.D. in theoretical physics from Charles Univ. in Prague in 2000) working on various aspects of physics of meso- and nanoscopic systems including nonequilibrium electronic quantum transport and hybrid superconducting systems. He is an expert in description of open quantum systems using advanced many-body methods such as generalized master equations or nonequilibrium Green’s functions. His interest in quantum dots attached to superconducting leads, for which he has been already awarded several national grant projects, dates back to his postdoctoral stay at the Niels Bohr Institute in Copenhagen and Visiting Professor stage at the Institute Néel in Grenoble. https://orcid.org/0000-0001-7014-4155

报告地点：M253 会议室

联系人：朱北沂 8264-9927