Wednesday, June 22, 2011

Acronym in physics: BCS standing for three physicists, who theoretically explained superconductivity

BCS stands for the physicists John Bardeen, Leon Cooper and Robert Schrieffer, who jointly developed a theory of superconductivity, what earned them the Nobel Prize in Physics in 1972 [1]. Their theory was originally published in 1957, giving an explanation of superconductivity, a phenomenon now known to occur in some 26 metallic elements and many compounds and alloys at (relatively) low temperatures [2]. The element, in which superconductivity was discovered in 1911, is mercury [3]: Heike Kammerlingh Onnes at Leiden University in the Netherlands cooled a sample of mercury to around 4 K and noticed that the electrical resistivity of the metal dropped to zero [4,5].

The BCS model is based on the two assumptions that (1) the superconducting particles are fermions [particles with half-integer spins: 1/2, 3/2, 5/2 … units of angular momentum, electron has spin 1/2] and that (2) they attract each other [5]. The key insight is that an electron moving through an elastic crystal lattice creates a slight distortion of the lattice, which, if persisting long enough, can affect a following electron. Cooper showed that this effect results in a current of bound electrons—the Cooper pairs—in superconductors [2,5]. Cooper pairing is a quantum effect.

BCS biographical notes [6]:
John Bardeen: American physicist, * May 23, 1908 in Madison (Wisconsin), † January 30, 1991 in Boston (Mass.), earned the Nobel Prize of Physics twice: first with Brattain and Shockley in 1956 for work on the transistor, second as mentioned above.
More at
Leon N. Cooper: American physicist, * February 2, 1930 in New York.
More at
John Robert Schrieffer: American physicist, * May 31, 1931 in Oak Park (Illinois).
More at

References and more to explore
[1] Thomas Burgner (2007): What is BCS Theory? see page 2 (and following pages) in
[2] Oxford Dictionary of Physics. Fourth and revised edition. Oxford University Press, New York, 2003.
[3] Hg, see solid state sniplink at
[4] J. Stajic, R. Coontz and I. Osborne: Happy 100th, Superconductivity! Science April 8, 2011, 322 (6026), page 189. [].
[5] Adrian Cho: Superconductivity's Smorgasbord Of Insights: A Movable Feast. Science April 8, 2011, 322 (6026), pp. 190-192. [].
[6] Autorenkollektiv: Lexikon der Naturwissenschaftler. Spektrum Akademischer Verlag, Heidelberg•Berlin, 2000.

No comments:

Post a Comment