Coherence and Coulomb blockade in single electron devices: a unified treatment of interaction effects

TL;DR

This paper presents a unified theoretical framework to analyze the interplay between Coulomb blockade and Kondo effect in quantum dots, revealing crossover behaviors and resonance phenomena depending on device parameters.

Contribution

The study introduces a self-consistent scheme combining phase and quasiparticle degrees of freedom to describe interaction effects in mesoscopic quantum dot devices.

Findings

Identifies crossover from Coulomb blockade to Kondo resonance at different temperatures.

Discovers inverse crossover where many-level Kondo resonance is suppressed at lower temperatures.

Shows emergence of single-level Kondo resonance at very low temperatures.

Abstract

We study the interplay between Coulomb blockade and the Kondo effect in quantum dots. We use a self-consistent scheme which describes mesoscopic devices in terms of a collective phase variable (slave rotor) and quasiparticle degrees of freedom. In the strong Coulomb blockade regime, we recover the description of metallic islands in terms of a phase only action. For a dot with well-separated levels, our method leads to the Kondo effect. We identify the regime where a crossover between the Coulomb blockade regime at high temperatures and the formation of a Kondo resonance at lower temperature takes place. In addition, we find that for a dot with many overlapping resonances, an {\it inverse crossover} can take place. A Kondo resonance which involves many levels within the dot is first formed, and this coherent state is suppressed by correlation effects at lower temperatures. A narrower Kondo resonance, due to a single level in the dot can emerge at even lower temperatures.