QUROPE Quantum Information Processing and Communication in Europe

We analyze the equilibrium and nonequilibrium 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 crosscorrelations are suppressed at frequencies below the Kondo scale and are characterized by a universal function that we determine numerically for T=0 temperature. For asymmetrical quantum dots dynamical spin accumulation resonance is found at the Kondo energy, ω∼TK. At higher temperatures surprising low-frequency anomalies related to overall spin conservation appear.