From Dilute Magnetic Alloys to Confined Nanostructures: Evolution of the Kondo Effect

Abstract

The Kondo problem occupies a central chapter in condensed matter physics, with a long history in dilute magnetic alloys and valence-fluctuating systems. Originally observed some 70 years ago as a minimum in the resistivity of dilute magnetic alloys, the Kondo effect has evolved in time into a paradigmatic example for strong electronic correlations in condensed matter physics. It pertains to the many-body screening of an impurity spin by the surrounding conduction electrons, leading to the formation of a strong scattering center at low temperatures. Besides the dramatic effect on the resistivity of otherwise pure metals, the Kondo effect is manifested in anomalous enhancements of thermodynamic and dynamic properties such as the specific heat, magnetic susceptibility, and thermopower to name a few. Over the past 40 years, the Kondo effect has played a pivotal role in the development of the field of strongly correlated electron systems. Many of the basic concepts and notions of the field have either been conceived or significantly advanced in the Kondo arena. Notable examples are the renormalization-group ideas of Anderson [1, 2] and Wilson [3]. Nearly all techniques of modern many-body physics have been applied to the problem, which continues to serve as an important testing ground for new approaches.