Kondo Physics in a Single Electron Transistor

TL;DR

This paper investigates Kondo physics in single electron transistors, demonstrating how localized electron spins interact with conduction electrons, leading to observable conductance phenomena consistent with theoretical predictions.

Contribution

It provides experimental evidence of Kondo effects in SETs, showing the formation of spin singlets and conductance enhancement under various conditions, aligning with theoretical models.

Findings

Zero-bias conductance increases for odd electron numbers

Kondo singlet state is sensitive to voltage, magnetic field, and temperature

Results agree with theoretical predictions of Kondo behavior

Abstract

The question of how localized electrons interact with delocalized electrons is central to many problems at the forefront of solid state physics. The simplest example is the Kondo phenomenon, which occurs when an impurity atom with an unpaired electron is placed in a metal, and the energy of the unpaired electron is far below the Fermi energy. At low temperatures a spin singlet state is formed between the unpaired localized electron and delocalized electrons at the Fermi energy. The confined droplet of electrons interacting with the leads of a single electron transistor (SET) is closely analogous to an impurity atom interacting with the delocalized electrons in a metal. (Meir, Wingreen and Lee, 1993) We report here measurements on a new generation of SETs that display all the aspects of the Kondo phenomenon: the spin singlet forms and causes an enhancement of the zero-bias conductance when the number of electrons on the artificial atom is odd but not when it is even. The singlet is altered by applying a voltage or magnetic field or by increasing the temperature, all in ways that agree with predictions. (Wingreen and Meir 1994)