Enhanced anti-ferromagnetic exchange between magnetic impurities in a superconducting host

ORAL

Abstract

It is generally believed that superconductivity only weakly affects the indirect exchange between magnetic impurities. If the distance $r$ between impurities is smaller than than the superconducting coherence length $(r<\xi)$, this exchange is thought to be dominated by RKKY interactions, identical to the those in a normal metallic host. This perception is based on a perturbative treatment of the exchange interaction. Here, we discuss a non-perturbative analysis and demonstrate that the presence of Yu-Shiba-Rusinov bound states induces a strong $1/r^2$ anti-ferromagnetic interaction that can dominate over conventional RKKY even at distances significantly smaller than the coherence length $(r\ll\xi)$. Experimental signatures, implications and applications are discussed.

*This work was supported, in part, by the NSF, DOE (FG02- 97ER25308), HQOC Fellowship and DARPA at Harvard and the DOE Contract No. DE-FG02-08ER46482 at Yale. JS is also supported by Condensed Matter Theory Center and the University of Maryland.

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Authors

  • Jay Sau

    • University of Maryland, College Park
    • Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
    • Condensed Matter Theory Center and Joint Quantum Institute, University of Maryland, College Park

  • Norman Yao

    • Harvard University

  • L. Glazman

    • Department of Physics, Yale University
    • Yale University

  • Eugene Demler

    • Harvard University
    • Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

  • Mikhail D. Lukin

    • Harvard University