Relevance of quantum fluctuations in the Anderson-Kondo model

TL;DR

This paper investigates how quantum fluctuations influence a localized spin coupled to an Anderson impurity, revealing their importance in ferromagnetic cases and classical behavior in antiferromagnetic cases.

Contribution

It demonstrates the significance of quantum fluctuations in the Anderson-Kondo model, especially for ferromagnetic coupling, providing insights into complex magnetic interactions in transition metal compounds.

Findings

Quantum fluctuations are crucial for ferromagnetic coupling.

Classical spin description suffices for antiferromagnetic coupling.

Quantum effects persist even for large localized spins.

Abstract

We study a localized spin coupled to an Anderson impurity to model the situation found in higher transition metal or rare earth compounds like e.g.\ LaMnO$_3$ or Gd monopnictides. We find that, even for large quantum numbers of the localized spin, quantum fluctuations play an essential role for the case of ferromagnetic coupling between the spin and the impurity levels. For antiferromagnetic coupling, a description in terms of a classical spin is appropriate.