Theory of ac spin current noise and spin conductance through a quantum dot in the Kondo regime: Equilibrium case

C. P. Moca, I. Weymann, G. Zaránd

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6 Citations (Scopus)

Abstract

We analyze the equilibrium frequency-dependent spin current noise and spin conductance through a quantum dot in the local moment regime. Spin current correlations behave markedly differently from charge correlations. Equilibrium spin correlations are characterized by two universal scaling functions in the absence of an external field: one of them is related to charge correlations, while the other one describes cross-spin correlations. We characterize these functions using a combination of perturbative and nonperturbative methods. We find that at low-temperatures spin cross correlations are suppressed at frequencies below the Kondo scale, T K, and a dynamical spin accumulation resonance is found at the Kondo energy, ω∼T K. At higher temperatures, T T K, surprising low-frequency anomalies related to overall spin conservation appear in the spin noise and spin conductance, and the Korringa rate is shown to play a distinguished role. The transient spin current response also displays universal and singular properties.

Original languageEnglish
Article number235441
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume84
Issue number23
DOIs
Publication statusPublished - Dec 27 2011

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Semiconductor quantum dots
quantum dots
Conservation
Temperature
cross correlation
conservation
anomalies
low frequencies
moments
scaling

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

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abstract = "We analyze the equilibrium frequency-dependent spin current noise and spin conductance through a quantum dot in the local moment regime. Spin current correlations behave markedly differently from charge correlations. Equilibrium spin correlations are characterized by two universal scaling functions in the absence of an external field: one of them is related to charge correlations, while the other one describes cross-spin correlations. We characterize these functions using a combination of perturbative and nonperturbative methods. We find that at low-temperatures spin cross correlations are suppressed at frequencies below the Kondo scale, T K, and a dynamical spin accumulation resonance is found at the Kondo energy, ω∼T K. At higher temperatures, T T K, surprising low-frequency anomalies related to overall spin conservation appear in the spin noise and spin conductance, and the Korringa rate is shown to play a distinguished role. The transient spin current response also displays universal and singular properties.",
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AU - Moca, C. P.

AU - Weymann, I.

AU - Zaránd, G.

PY - 2011/12/27

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N2 - We analyze the equilibrium frequency-dependent spin current noise and spin conductance through a quantum dot in the local moment regime. Spin current correlations behave markedly differently from charge correlations. Equilibrium spin correlations are characterized by two universal scaling functions in the absence of an external field: one of them is related to charge correlations, while the other one describes cross-spin correlations. We characterize these functions using a combination of perturbative and nonperturbative methods. We find that at low-temperatures spin cross correlations are suppressed at frequencies below the Kondo scale, T K, and a dynamical spin accumulation resonance is found at the Kondo energy, ω∼T K. At higher temperatures, T T K, surprising low-frequency anomalies related to overall spin conservation appear in the spin noise and spin conductance, and the Korringa rate is shown to play a distinguished role. The transient spin current response also displays universal and singular properties.

AB - We analyze the equilibrium frequency-dependent spin current noise and spin conductance through a quantum dot in the local moment regime. Spin current correlations behave markedly differently from charge correlations. Equilibrium spin correlations are characterized by two universal scaling functions in the absence of an external field: one of them is related to charge correlations, while the other one describes cross-spin correlations. We characterize these functions using a combination of perturbative and nonperturbative methods. We find that at low-temperatures spin cross correlations are suppressed at frequencies below the Kondo scale, T K, and a dynamical spin accumulation resonance is found at the Kondo energy, ω∼T K. At higher temperatures, T T K, surprising low-frequency anomalies related to overall spin conservation appear in the spin noise and spin conductance, and the Korringa rate is shown to play a distinguished role. The transient spin current response also displays universal and singular properties.

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