Self-portrait by Kamerlingh Onnes
AIP Emilio Segre Visual Archives
Kamerlingh Onnes, after liquefying helium for the first time in 1908, devoted his laboratory at the University of Leiden (Holland) to measuring the properties of matter from -271 °C to -259 °C. The measurement of electrical resistance was one of the properties that interested him most, and in 1911 he observed that the electrical resistance of mercury disappeared below a certain critical temperature. Soon after verifying the phenomenon in Pb and Tl, he realised that this was a new behaviour of matter appearing at low temperatures; he had just discovered superconductivity. For his work in low-temperature research, he was awarded the 1913 Nobel Prize in Physics.
In 1957, J. Bardeen, L. Cooper and R. Schrieffer enunciated their theory, known as BSC, which for the first time explained almost all the properties of superconducting materials and won the 1972 Nobel Prize in Physics. The BCS theory postulates that, in the superconducting state, there is an attractive interaction between electrons through deformations of the metal lattice that couple them into pairs (Cooper pairs). These pairs are capable of carrying current without electrical resistance.
In 1986, J.C. Bednorz and K.A. Müller, at IBM Laboratories in Switzerland, discovered superconductivity in ceramic materials and at temperatures above the limit. This result earned them the 1987 Nobel Prize in Physics and started a revolution in the field as materials were quickly found that were capable of working at temperatures above the boiling point of liquid nitrogen (-196 °C), which allows them to be cooled much more easily and economically. These families of materials, which are called high-temperature superconductors, SATs, have led to increased technological interest in developing new applications.
But what is superconductivity?
