Kondo effect

The Kondo effect describes the abnormal behavior of the electrical resistance in metals with magnetic imperfections .

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

A monotonous decaying resistance up to a residual resistance in the case of (non-magnetic) contamination and lattice vibrations (e.g. with copper, gold) ${\ displaystyle T = 0}$

The onset of superconductivity below a critical temperature - the complete disappearance of electrical resistance (e.g. with lead, niobium).

{\ displaystyle T_ {c}}

In 1964, Jun Kondo was able to show in perturbation theory that the electrical resistance diverges logarithmically for low temperatures due to magnetic impurities , since the conduction electrons are scattered by localized magnetic electrons. This effect creates a minimum resistance. The temperature dependence of the electrical resistance including the Kondo effect is described by the following formula:

{\ displaystyle \ rho (T) = \ rho _ {0} + aT ^ {2} + c_ {m} \ ln {\ frac {\ mu} {T}} + bT ^ {5}.}

It is the residual resistance, the contribution of the Fermi liquid and the term describes the resistance component formed by the electron- phonon induced interaction. ${\ displaystyle \ rho _ {0}}$ ${\ displaystyle aT ^ {2}}$ ${\ displaystyle bT ^ {5}}$

Jun Kondo derived the logarithmic dependence from the Kondo model named after him . The collapse of the perturbation theory below the so-called Kondo is as Kondoproblem designated and could in subsequent batches by the so-called "Poor Man's scaling" of ( Philip Warren Anderson , to the finite limit of resistance for temperatures close to 1970) are dissolved absolute zero to explain . Anderson's scaling approach was initially only a qualitative hypothesis and was only verified and specified in 1974 by Kenneth G. Wilson using the method of the renormalization group .

Individual evidence

↑ WJ de Haas, JH de Boer, GJ van de Berg: The electrical resistance of gold, copper and lead at low temperatures . In: Physica . tape 1 , no. 7 . Utrecht May 1934, p. 1115-1124 , doi : 10.1016 / S0031-8914 (34) 80310-2 , bibcode : 1934Phy ..... 1.1115D .
^ J. Kondo: Resistance Minimum in Dilute Magnetic Alloys . In: Progress of Theoretical Physics . tape 32 , 1964, pp. 37 , doi : 10.1143 / PTP.32.37 .
↑ PW Anderson: A poor man's derivation of scaling laws for the Kondo problem . In: J. Phys. C: Solid State Phys. tape 3 , no. 12 , 1970, pp. 2436 , doi : 10.1088 / 0022-3719 / 3/12/008 .

Web links

Jun Kondo's website ( Memento from August 16, 2002 in the Internet Archive ) (English / Japanese)
Kondo Effect - 40 years after its discovery ( Memento of December 20, 2004 in the Internet Archive ) - Special edition of the Journal of the Japanese Physical Society (English)
Alex Hewson: Kondo Effect. Scholarpedia 2009.

[1] WJ de Haas, JH de Boer, GJ van de Berg: The electrical resistance of gold, copper and lead at low temperatures . In: Physica . tape 1 , no. 7 . Utrecht May 1934, p. 1115-1124 , doi : 10.1016 / S0031-8914 (34) 80310-2 , bibcode : 1934Phy ..... 1.1115D .

[2] J. Kondo: Resistance Minimum in Dilute Magnetic Alloys . In: Progress of Theoretical Physics . tape 32 , 1964, pp. 37 , doi : 10.1143 / PTP.32.37 .

[3] PW Anderson: A poor man's derivation of scaling laws for the Kondo problem . In: J. Phys. C: Solid State Phys. tape 3 , no. 12 , 1970, pp. 2436 , doi : 10.1088 / 0022-3719 / 3/12/008 .