Two-impurity Yu-Shiba-Rusinov states in coupled quantum dots

J. C. Estrada Saldaña, A. Vekris, R. Žitko, G. Steffensen, P. Krogstrup, J. Paaske, K. Grove-Rasmussen, and J. Nygård
Phys. Rev. B 102, 195143 – Published 23 November 2020

Abstract

Using double quantum dots as the weak link of a Josephson junction, we realize the superconducting analog of the celebrated two-impurity Kondo model. The device shows a cusped current-voltage characteristic, which can be modeled by an overdamped circuit relating the observed cusp current to the Josephson critical current. The gate dependence of the cusp current and of the subgap spectra are used as complementary ground-state indicators to demonstrate gate-tuned changes of the ground state from an interdot singlet to independently screened Yu-Shiba-Rusinov (YSR) singlets. In contrast to the two-impurity Kondo effect in normal-state systems, the crossover between these two singlets is heralded by quantum phase boundaries to nearby doublet YSR phases in which only a single spin is screened.

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  • Received 19 September 2020
  • Accepted 5 November 2020

DOI:https://doi.org/10.1103/PhysRevB.102.195143

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

J. C. Estrada Saldaña1, A. Vekris1,2, R. Žitko3,4, G. Steffensen1, P. Krogstrup1,5, J. Paaske1, K. Grove-Rasmussen1, and J. Nygård1,*

  • 1Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
  • 2Sino-Danish Center for Education and Research (SDC) SDC Building, Yanqihu Campus, University of Chinese Academy of Sciences, 380 Huaibeizhuang, Huairou District, 101408 Beijing, China
  • 3Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
  • 4Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia
  • 5Microsoft Quantum Materials Lab Copenhagen, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark

  • *Corresponding author: nygard@nbi.ku.dk

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Issue

Vol. 102, Iss. 19 — 15 November 2020

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