<i>s</i>-<i>d</i>Exchange Interaction in a Superconductor

Soda, Toshio; Matsuura, Tamifusa; Nagaoka, Yosuke

doi:10.1143/ptp.38.551

Cited by 69 publications

(66 citation statements)

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“…Recall here that the QD-S system is equivalent to a magnetic impurity model embedded in a superconductor, which has been studied for dilute magnetic alloys. [38][39][40][41] As discussed in refs. 38-41, the ground state of the QD-S system is a nonmagnetic singlet or a magnetic doublet.…”

Section: Implications Of the Conductance Maximummentioning

confidence: 99%

Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads

2007

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We study transport through a quantum dot coupled to normal and superconducting leads using the numerical renormalization group method. We show that the low-energy properties of the system are described by the local Fermi liquid theory despite of the superconducting correlations penetrated into the dot due to a proximity effect. We calculate the linear conductance due to the Andreev reflection in the presence of the Coulomb interaction. It is demonstrated that the maximum structure appearing in the conductance clearly characterizes a crossover between two distinct spin-singlet ground states, i.e. the superconducting singlet state and the Kondo singlet state. It is further elucidated that the gate-voltage dependence of the conductance shows different behavior in the superconducting singlet region from that in the Kondo singlet region.

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Section: Implications Of the Conductance Maximummentioning

confidence: 99%

Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads

2007

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“…The limit T K ≪ ∆ was considered following the work of Shiba (Müller-Hartmann, 1973;Soda et al, 1967;Zittartz and Müller-Hartmann, 1970), and the position of the localized excited state was found with various degrees of accuracy. Notice that in this regime the localized state lies close to the gap edge as it does for ferromagnetic coupling.…”

Section: Antiferromagnetic Couplingmentioning

confidence: 99%

Impurity-induced states in conventional and unconventional superconductors

2006

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We review recent developments in our understanding of how impurities influence the electronic states in the bulk of superconductors. Our focus is on the quasi-localized states in the vicinity of impurity sites in conventional and unconventional superconductors and our goal is to provide a unified framework for their description. The non-magnetic impurity resonances in unconventional superconductors are directly related to the Yu-Shiba-Rusinov states around magnetic impurities in conventional s-wave systems. We review the physics behind these states, including quantum phase transition between screened and unscreened impurity, and emphasize recent work on d-wave superconductors. The bound states are most spectacularly seen in scanning tunneling spectroscopy measurements on high-Tc cuprates, which we describe in detail. We also discuss very recent progress on the states coupled to impurity sites which have their own dynamics, and impurity resonances in the presence of an order competing with superconductivity. Last part of the review is devoted to influence of local deviations of the impurity concentration from its average value on the density of states in s-wave superconductors. We review how these fluctuations affect the density of states and show that s-wave superconductors are, strictly speaking, gapless in the presence of an arbitrarily small concentration of magnetic impurities.

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“…showing up for superconducting metals containing magnetic impurities, was first studied several decades ago. [4][5][6][7][8][9][10][11][12][13] The Kondo temperature T K and the superconducting gap ∆ are the two competing energy scales which govern the low-energy physics of such systems. If T K ≫ ∆, local magnetic moments are screened by virtue of the Kondo effect.…”

Section: Introductionmentioning

confidence: 99%

Josephson current through a single Anderson impurity coupled to BCS leads

2008

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We investigate the Josephson current J(φ) through a quantum dot embedded between two superconductors showing a phase difference φ. The system is modeled as a single Anderson impurity coupled to BCS leads, and the functional and the numerical renormalization group frameworks are employed to treat the local Coulomb interaction U . We reestablish the picture of a quantum phase transition occurring if the ratio between the Kondo temperature TK and the superconducting energy gap ∆ or, at appropriate TK /∆, the phase difference φ or the impurity energy is varied. We present accurate zero-as well as finite-temperature T data for the current itself, thereby settling a dispute raised about its magnitude. For small to intermediate U and at T = 0 the truncated functional renormalization group is demonstrated to produce reliable results without the need to implement demanding numerics. It thus provides a tool to extract characteristics from experimental currentvoltage measurements.

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s-dExchange Interaction in a Superconductor

Cited by 69 publications

References 0 publications

Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads

Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads

Impurity-induced states in conventional and unconventional superconductors

Josephson current through a single Anderson impurity coupled to BCS leads

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