Andreev Bound States in the Kondo Quantum Dots Coupled to Superconducting Leads

TL;DR

This paper investigates the subgap Andreev states in a Kondo quantum dot coupled to superconducting leads using the NRG method, revealing states both below and above the Fermi level, contrasting previous NCA results.

Contribution

It provides a detailed analysis of Andreev states in Kondo quantum dots with superconducting leads using NRG, challenging prior NCA findings.

Findings

Andreev states observed both below and above the Fermi level.

Contradicts previous NCA results on Andreev states.

Uses NRG method for accurate analysis.

Abstract

We have studied the Kondo quantum dot coupled to two superconducting leads and investigated the subgap Andreev states using the NRG method. Contrary to the recent NCA results [Clerk and Ambegaokar, Phys. Rev. B 61, 9109 (2000); Sellier et al., Phys. Rev. B 72, 174502 (2005)], we observe Andreev states both below and above the Fermi level.