Kondo screening of Andreev bound states in a normal metal–quantum dot–superconductor system

Lin Li, Zhan Cao, Tie-Feng Fang, Hong-Gang Luo, and Wei-Qiang Chen
Phys. Rev. B 94, 165144 – Published 19 October 2016

Abstract

Motivated by experimental observation of the Kondo-enhanced Andreev transport [R. S. Deacon et al., Phys. Rev. B 81, 121308(R) (2010)] in a hybrid normal metal–quantum dot–superconductor (N-QD-S) device, we theoretically study the Kondo effect in such a device and clarify the different roles played by the normal and superconducting leads. Due to the Andreev reflection in a QD-S system, a pair of Andreev energy levels form in the superconducting gap, which is able to carry the magnetic moment if the ground state of the QD is a magnetic doublet. In this sense, the Andreev energy levels play a role of effective impurity levels. When the normal lead is coupled to the QD-S system, on the one hand, the Andreev energy levels broaden to form the so-called Andreev bound states (ABSs); on the other hand, it can screen the magnetic moment of the ABSs. By tuning the couplings between the QD and the normal (superconducting) leads, the ABSs can simulate the Kondo, mixed-valence, and even empty orbit regimes of the usual single-impurity Anderson model. The above picture is confirmed by the Green's function calculation of the hybrid N-QD-S Anderson model and is also able to explain qualitatively experimental phenomena observed by Deacon et al. These results can further stimulate related experimental study in the N-QD-S systems.

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  • Received 18 December 2015
  • Revised 1 February 2016

DOI:https://doi.org/10.1103/PhysRevB.94.165144

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Lin Li1, Zhan Cao2, Tie-Feng Fang2, Hong-Gang Luo2,3,*, and Wei-Qiang Chen1,†

  • 1Department of Physics, Southern University of Science and Technology of China, Shenzhen 518005, China
  • 2Center of Interdisciplinary Studies and Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China
  • 3Beijing Computational Science Research Center, Beijing 100084, China

  • *luohg@lzu.edu.cn
  • chen.wq@sustc.edu.cn

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Issue

Vol. 94, Iss. 16 — 15 October 2016

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