The Kondo Screening Cloud

Renormalization group theory of the Kondo effect predicts that an impurity spin is screened by a conduction electron spread over a large distance of order

.1 to 1 micron. This review has the following sections: 1. The Kondo effect and the screening cloud, 2. Non-observation of the Kondo cloud in conventional experiments, 3. Kondo effect in transmission through a quantum dot, 4. Observing the screening cloud in persistent current experiments, 5. Side-coupled quantum dot, 6. Conclusions