Two-stage Kondo effect in side-coupled quantum dots: Renormalized perturbative scaling theory and Numerical Renormalization Group analysis

TL;DR

This paper investigates the two-stage Kondo effect in a side-coupled quantum dot system, combining renormalized perturbative scaling theory with numerical renormalization group analysis to understand conductance and noise characteristics.

Contribution

It introduces a renormalized scaling theory that accurately describes the crossover in conductance, validated by numerical NRG results, for the two-stage Kondo effect in quantum dots.

Findings

The theory captures the conductance crossover effectively.

NRG results agree with analytical formulas.

Frequency-dependent noise spectrum is characterized.

Abstract

We study numerically and analytically the dynamical (AC) conductance through a two-dot system, where only one of the dots is coupled to the leads but it is also side-coupled to the other dot through an antiferromagnetic exchange (RKKY) interaction. In this case the RKKY interaction gives rise to a ``two-stage Kondo effect'' where the two spins are screened by two consecutive Kondo effects. We formulate a renormalized scaling theory that captures remarkably well the cross-over from the strongly conductive correlated regime to the low temperature low conductance state. Our analytical formulas agree well with our numerical renormalization group results. The frequency dependent current noise spectrum is also discussed.