Interplay of electromagnetic noise and Kondo effect in quantum dots

TL;DR

This paper explores how electromagnetic noise affects the Kondo effect in quantum dots, revealing conductance anomalies and the importance of circuit impedance in low-temperature behavior.

Contribution

It demonstrates the influence of electromagnetic environment on Kondo physics, linking dynamical Coulomb blockade effects to Luttinger liquid behavior and providing a quantitative analysis of Kondo temperature dependence.

Findings

Low-energy properties resemble those in Luttinger liquids.

Conductance can vanish at low temperatures despite screening.

Kondo temperature depends on the full impedance spectrum.

Abstract

We investigate the influence of an electromagnetic environment, characterized by a finite impedance $Z(\omega)$, on the Kondo effect in quantum dots. The circuit voltage fluctuations couple to charge fluctuations in the dot and influence the spin exchange processes transferring charge between the electrodes. We discuss how the low-energy properties of a Kondo quantum dot subject to dynamical Coulomb blockade resemble those of Kondo impurities in Luttinger liquids. Using previous knowledge based on the bosonization of quantum impurity models, we show that low-voltage conductance anomalies appear at zero temperature. The conductance can vanish at low temperatures even in presence of a screened impurity spin. Moreover, the quantitative determination of the corresponding Kondo temperature depends on the full frequency-dependent impedance of the circuit. This is demonstrated by a weak-coupling calculation in the Kondo interaction, taking into account the full distribution $P(E)$ of excited environmental modes.