Theory of frequency-dependent spin current noise through correlated quantum dots

TL;DR

This paper investigates the frequency-dependent spin current noise and conductance in quantum dots, revealing unique behaviors of spin correlations, including suppression at low frequencies and resonances near the Kondo energy.

Contribution

It provides a detailed analysis of spin current noise in quantum dots, highlighting differences from charge correlations and identifying universal and resonance phenomena.

Findings

Equilibrium spin cross-correlations are suppressed below the Kondo scale.

Universal function characterizes spin correlations at zero temperature.

Dynamical spin accumulation resonance occurs near the Kondo energy in asymmetric dots.

Abstract

We analyze the equilibrium and non-equilibrium frequency-dependent spin current noise and spin conductance through a quantum dot in the local moment regime. Spin current correlations are shown to behave markedly differently from charge correlations: Equilibrium spin cross-correlations are suppressed at frequencies below the Kondo scale, and are characterized by a universal function that we determine numerically for zero temperature. For asymmetrical quantum dots dynamical spin accumulation resonance is found for frequencies of the order of the Kondo energy. At higher temperatures surprising low-frequency anomalies related to overall spin conservation appear.