Negative-$U$ Anisotropic Charge Kondo Effect in a Triple Quantum Dot

TL;DR

This paper predicts a novel negative-$U$ Anderson impurity in a triple quantum dot system, exhibiting a charge Kondo effect with tunable phases, and suggests experimental detection via conductance measurements.

Contribution

It introduces a new negative-$U$ impurity model in triple quantum dots and analyzes its phase transition using bosonization, linking it to the anisotropic Kondo model.

Findings

Identification of two distinct charge fluctuation phases

Prediction of a measurable phase transition via conductance

Establishment of a link between quantum dot behavior and Kondo physics

Abstract

We predict a new type of the negative-$U$ Anderson impurity formed in a triple quantum dot. The two dots of the system behave as a negative-$U$ impurity preferring zero or double electron occupancy rather than single occupancy, and the third dot stabilizes the attractive interaction of $U < 0$ via Coulomb repulsion. Using a bosonization method, we find that the system has the two different phases of massive or vanishing charge fluctuations between the two occupancies at low temperature, which are equivalent with the antiferromagnetic and ferromagnetic phases of the anisotropic Kondo model, respectively. The phase transition is experimentally accessible and identifiable by electron conductance, offering the possibility of experimentally exploring the anisotropic Kondo model.