Kondo effect

The Kondo effect describes the anomalous behavior of the electrical resistance in metals with magnetic impurities.

1934 observed walking Johannes de Haas, Jan Hendrik de Boer and GJ van de Berg a minimum in the electrical resistance of a gold sample with magnetic impurities at low temperatures, which was not compatible with the former understanding of the electrical resistance. After that time understanding there were two types of low-temperature behavior of resistance:

• A monotonic decay resistance to a residual resistance by ( non-magnetic ) impurities and lattice vibrations (eg, copper, gold )
• Inserting superconducting below a critical temperature, - the complete disappearance of the electrical resistance (for example, of lead, niobium).

June 1964 Kondo could show perturbatively that the electrical resistance at low temperatures diverges logarithmically due to magnetic impurities, because the conduction electrons are scattered by localized magnetic electrons. This effect causes the emergence of a resistance minimum. The temperature dependence of resistance, including the electronic Kondo effect is described by the following formula:

Here, the radical resistance, the contribution of the Fermi liquid and the term describes the resistance component which is caused by electron-phonon interaction.

June Kondo has derived the logarithmic dependence of the Kondo model named after him. The collapse of the perturbation theory below the so-called Kondo is called Kondoproblem and could " 's scaling Poor Man" be detached from ( Philip W. Anderson, 1970) by the so-called in later approaches to the finite limit of the resistance to temperatures near absolute zero to explain. The scaling approach of Anderson was initially only a qualitative hypothesis and was only in 1974 verified and clarified by Kenneth G. Wilson by the method of the renormalization group.