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SUPERCONDUCTIVITY |
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Superconductivity - the complete loss of electrical resistance in some materials when they are subject to sufficiently low temperatures - is a phenomenon that cannot be explained by the ideas of classical physics. In this series of articles I will attempt to explain what superconductivity is, some of the effects that superconducting materials exhibit, and how superconductivity arises. |
Superconductivity was discovered in 1911 by a Dutch physicist, Heike Kamerlingh Onnes. Onnes was investigating the resistance of mercury at very low temperatures, and he observed that for temperatures below about 4 K, the resistance of mercury dropped to levels too small to be measured. Onnes referred to this state as the "superconducting state". It was to be another 46 years before a theoretical explanation of superconductivity was published. This theory, developed by John Bardeen, Leon Cooper and John Schrieffer, was a technically advanced quantum mechanical theory of superconductivity and the superconducting state. The three physicists won the 1972 Nobel Prize for Physics as a result of this work.
The first article sets the scene by discussing how the electrical resistance of a conductor is normally expected to vary with temperature. The second article then introduces superconductivity and the superconducting state, and discusses some of the basic properties of the superconducting state. The third article discusses the Meissner effect, and the fourth article discusses Type 1 and Type 2 superconductors. The final two articles touch on the physical origins of superconductivity and the one of the most important concepts in the theory of superconductivity, namely the Cooper pair.
Note that the words and interpretation here are my own. I have made no attempt at a rigorous treatment of superconductivity, and as such have neglected many aspects of the subject (in particular, the phenomenon of high-temperature superconductivity). I have discussed the parts of the theory that interest me, and my aim is only to give a flavour of the phenomenon of superconductivity, and what it is all about.