Time-Dependent Transport Through Quantum-Impurity Systems with Kondo Resonance

TL;DR

This paper studies the time-dependent electron transport in quantum-impurity systems within the Kondo regime, revealing oscillatory behaviors influenced by temperature and electron interactions, using the hierarchical equations of motion approach.

Contribution

It introduces a detailed analysis of current oscillations in quantum-impurity systems under time-dependent conditions, highlighting the effects of temperature and electron-electron interactions.

Findings

Current oscillations are due to electron tunneling coherence.

Temperature suppresses oscillation amplitude via Kondo effect inhibition.

Double impurities show larger oscillation amplitudes than single impurities.

Abstract

We investigate the time-dependent transport properties of single and double quantum-impurity systems based on the hierarchical equations of motion (HEOM) approach. In the Kondo regime, the dynamical current in both cases is found oscillating due to the temporal coherence of electrons tunneling through the device, which shares the same mechanism as the single-level resonance without e-e interactions but shows some different characteristics. For single quantum-impurity systems, the temperature T plays an inhibitory action to the oscillations of dynamic current through its suppression to the Kondo effects. The amplitude of the current oscillations is attenuated by the e-e interaction $U$ in the Kondo regime. The frequency of the current oscillation is found almost independent of T and U. For parallel-coupling double quantum-impurity systems, the oscillation of the current shows similar behaviors to the single one, but with two-to-three times larger amplitudes. At the limit of small inter-impurity coupling the oscillation of the current exhibits enhanced characters while it is weakened at the other limit.