Two-Impurity Anderson-Kondo Model: first order Impurity-correlation

TL;DR

This paper investigates the first-order inter-impurity correlation in the Two-Impurity Anderson-Kondo model, revealing the formation of Kondo Doublets that influence spin correlations in quantum dot systems.

Contribution

It introduces the concept of first-order impurity correlation leading to Kondo Doublets, offering new insights into spin interactions beyond second-order RKKY effects.

Findings

Kondo Doublets are responsible for the initial Kondo screening stage.

The system favors ferromagnetic dot-dot spin correlation.

Parallel spin alignment is promoted for effective screening.

Abstract

We analyze the consequences of a first-order (in the effective Kondo coupling) inter-impurity correlation present in the Two-Impurity Anderson Hamiltonian. This correlation generates a pair of Kondo Doublet states which are responsible for the first (higher energy) Kondo stage of these systems. Applied to systems of quantum dots in a semiconductor heterolayer, these Doublets predict a mainly ferromagnetic dot-dot spin correlation which is different than the expected from the second-order RKKY interaction. In order to effectively screen both dots, a parallel alignment of the dot-spins is favored by the interaction.