Dynamics of capacitively coupled double quantum dots

TL;DR

This paper investigates the complex behavior of a double quantum dot system with capacitive coupling, analyzing how its electronic properties evolve across different regimes and phases using numerical renormalization group techniques.

Contribution

It provides a detailed analysis of the single-particle dynamics and conductance in double quantum dots, highlighting the transition from spin-Kondo to charge-Kondo regimes and the quantum phase transition to a charge-ordered phase.

Findings

Identification of universal low-energy scaling behavior

Characterization of the non-Fermi liquid nature of the charge-ordered phase

Analysis of symmetry breaking effects on system dynamics

Abstract

We consider a double dot system of equivalent, capacitively coupled semiconducting quantum dots, each coupled to its own lead, in a regime where there are two electrons on the double dot. Employing the numerical renormalization group, we focus here on single-particle dynamics and the zero-bias conductance, considering in particular the rich range of behaviour arising as the interdot coupling is progressively increased through the strong coupling (SC) phase, from the spin-Kondo regime, across the SU(4) point to the charge-Kondo regime; and then towards and through the quantum phase transition to a charge-ordered (CO) phase. We first consider the two-self-energy description required to describe the broken symmetry CO phase, and implications thereof for the non-Fermi liquid nature of this phase. Numerical results for single-particle dynamics on all frequency scales are then considered, with particular emphasis on universality and scaling of low-energy dynamics throughout the SC phase. The role of symmetry breaking perturbations is also briefly discussed.