Spectral properties of locally correlated electrons in a Bardeen–Cooper–Schrieffer superconductor

TLDR: In this paper, the spectral properties of a locally correlated site embedded in a BCS superconducting medium were analyzed by means of numerical renormalization group calculations, and the position and weight of the Andreev bound states were given for all relevant parameters.

Abstract: We present a detailed study of the spectral properties of a locally correlated site embedded in a Bardeen–Cooper–Schrieffer (BCS) superconducting medium. To this end the Anderson impurity model with a superconducting bath is analysed by means of numerical renormalization group calculations. We calculate one-and two-particle dynamic response functions to elucidate the spectral excitations and the nature of the ground state for different parameter regimes with and without particle–hole symmetry. The position and weight of the Andreev bound states is given for all relevant parameters. We present phase diagrams for the different ground state parameter regimes. This work is also relevant for dynamical mean field theory extensions with superconducting symmetry breaking.