The Andreev states of a superconducting quantum dot: mean field versus exact numerical results

A Martín-Rodero, A Levy Yeyati
2012 Journal of Physics: Condensed Matter  
We analyze the spectral density of a single level quantum dot coupled to superconducting leads focusing on the Andreev states appearing within the superconducting gap. We use two complementary approaches: the numerical renormalization group and the Hartree-Fock approximation. Our results show the existence of up to four bound states within the gap when the ground state is a spin doublet (\pi\ phase). Furthermore the results demonstrate the reliability of the mean field description within this
more » ... ption within this phase. This is understood from a complete correspondence that can be established between the exact and the mean field quasiparticle excitation spectrum
doi:10.1088/0953-8984/24/38/385303 pmid:22945559 fatcat:pyvbczx5dzbpxd5rox5xvmbugu