The Kondo Box: A Magnetic Impurity in an Ultrasmall Metallic Grain

TL;DR

This paper investigates how the Kondo effect manifests in ultrasmall metallic grains with a magnetic impurity, revealing parity-dependent effects on the Kondo resonance and conductance, with implications for nanoscale electronic devices.

Contribution

It introduces the concept of a 'Kondo box' and analyzes the impact of finite level spacing and electron parity on the Kondo resonance and conductance properties.

Findings

Kondo resonance is suppressed when level spacing exceeds Kondo temperature.

Parity of electron number influences the Kondo effect and conductance features.

Kondo-induced Fano resonances are observable and depend on temperature and level spacing.

Abstract

We study the Kondo effect generated by a single magnetic impurity embedded in an ultrasmall metallic grain, to be called a ``Kondo box''. We find that the Kondo resonance is strongly affected when the mean level spacing in the grain becomes larger than the Kondo temperature, in a way that depends on the parity of the number of electrons on the grain. We show that the single-electron tunneling conductance through such a grain features Kondo-induced Fano-type resonances of measurable size, with an anomalous dependence on temperature and level spacing.