Quantum phase transition in quantum dot trimers

TL;DR

This paper explores a system of three quantum dots arranged in a triangle, revealing a quantum phase transition between different magnetic regimes and showing how the Kondo effect manifests near this transition, with potential experimental implications.

Contribution

It demonstrates the existence of a quantum phase transition between ferro- and antiferromagnetic Kondo regimes in a triangular quantum dot system, analyzed through numerical and physical methods.

Findings

Identification of a quantum phase transition controlled by interdot couplings

Emergence of Kondo effect near the transition at finite temperatures

Distinct magnetic regimes accessible via tuning system parameters

Abstract

We investigate a system of three tunnel-coupled semiconductor quantum dots in a triangular geometry, one of which is connected to a metallic lead, in the regime where each dot is essentially singly occupied. Both ferro- and antiferromagnetic spin-1/2 Kondo regimes, separated by a quantum phase transition, are shown to arise on tuning the interdot tunnel couplings and should be accessible experimentally. Even in the ferromagnetically-coupled local moment phase, the Kondo effect emerges in the vicinity of the transition at finite temperatures. Physical arguments and numerical renormalization group techniques are used to obtain a detailed understanding of the problem.