Spectral properties of locally correlated electrons in a Bardeen–Cooper–Schrieffersuperconductor

Abstract

We present a detailed study of the spectral properties of a locally correlated site embeddedin a Bardeen–Cooper–Schrieffer (BCS) superconducting medium. To this end the Andersonimpurity model with a superconducting bath is analysed by means of numericalrenormalization group calculations. We calculate one-and two-particle dynamic responsefunctions to elucidate the spectral excitations and the nature of the ground state fordifferent parameter regimes with and without particle–hole symmetry. The position andweight of the Andreev bound states is given for all relevant parameters. We present phasediagrams for the different ground state parameter regimes. This work is also relevant fordynamical mean field theory extensions with superconducting symmetry breaking.