High-order current correlation functions in Kondo systems

TL;DR

This paper investigates the third current cumulant in Kondo quantum dot systems, revealing strong non-linear voltage dependence across different regimes and recovering linearity only at high voltages.

Contribution

It introduces a modified Keldysh technique to calculate the third current cumulant in Kondo systems across various regimes, highlighting non-linear behaviors.

Findings

Third cumulant exhibits strong non-linear voltage dependence.

Linear dependence on voltage is only observed at high voltages.

Different regimes show distinct fluctuation characteristics.

Abstract

We examine the statistics of current fluctuations in a junction with a quantum dot described by Kondo Hamiltonian. With the help of modified Keldish technique we calculate the third current cumulant. As a function of ratio $v=eV/T_{K}$ the 3rd cumulant was obtained for three different regimes: Fermi liquid regime (v<1), crossover interval ($v\geq1$) and RG limit (v>>1). Unlike the case of noninteracting dot, 3rd cumulant shows strong non-linear voltage dependence. Only in the asymptotical limit of large voltages the linear dependence on $V$ is recovered.