Interplay between Hund's rule and Kondo effect in a quantum dot

TL;DR

This paper explores how Hund's rule and the Kondo effect interact in a multi-electron quantum dot, revealing complex electronic states and unusual Kondo signatures that serve as a model for Hund's metals.

Contribution

It demonstrates the interplay between Hund's rule and Kondo physics in a multi-orbital quantum dot, highlighting its role as a model for Hund's metals.

Findings

Maximum addition energy at half-filling explained by Hund's exchange

Observation of Kondo zero-bias anomalies with unexpected widths

Quantum dot acts as a multi-orbital Kondo impurity with Hund's interaction

Abstract

The interaction between localized spins on a quantum dot and free electrons in the reservoirs forms a many-particle entangled system giving rise to the Kondo effect. Here, we investigate electron transport in the third shell of a gate-defined GaAs quantum dot. The addition energy shows a maximum at half-filling of the shell which can be described analytically with Hund's rule exchange interaction. For 7 to 11 electrons occupying the quantum dot Zero-bias anomalies characteristic for the Kondo effect are observed, but with unexpected widths. Here the quantum dot has to be described as a multi-orbital Kondo impurity with Hund's interaction. In this way this quantum dot can be seen as a model system for a Hund's coupled mixed-valence quantum impurity as appearing in Hund's metals where local ferromagnetic interactions between orbitals lead to the emergence of complex electronic states.