Kondo resonance narrowing in d- and f-electron systems

TL;DR

This paper develops a scaling theory showing how Hund's interactions cause exponential narrowing of the Kondo resonance in d- and f-electron systems, affecting magnetic and electronic properties.

Contribution

It introduces a simple scaling theory predicting exponential Kondo temperature reduction due to Hund's interactions, linking to experimental and numerical observations.

Findings

Exponential reduction of Kondo temperature with spin S.

Kondo resonance narrowing observed in d-electron alloys and Hubbard models.

Implications for Mott transition and ESR linewidth in f-electron materials.

Abstract

By developing a simple scaling theory for the effect of Hund's interactions on the Kondo effect, we show how an exponential narrowing of the Kondo resonance develops in magnetic ions with large Hund's interaction. Our theory predicts an exponential reduction of the Kondo temperature with spin S of the Hund's coupled moment, a little-known effect first observed in d-electron alloys in the 1960's, and more recently encountered in numerical calculations on multi-band Hubbard models with Hund's interactions. We discuss the consequences of Kondo resonance narrowing for the Mott transition in d-band materials, particularly iron pnictides, and the narrow ESR linewidth recently observed in ferromagnetically correlated f-electron materials.