The 2003 Physics Nobel Prize

The 2003 Physics Nobel Prize goes to Alexei A. Abrikosov (Institute for Physical Problems in Moscow and now at Argonne National Laboratory near Chicago), Vitaly L. Ginzburg (Lebedev Physical Institute, Moscow) and Anthony J. Leggett (University of Illinois, Urbana).

The award goes for work done on systems that operate under two regimes very far from human experience: the quantum realm and the low-temperature realm. In superconductivity, a current of electrons flowing through a material undergoes a change in behavior: normally reluctant to associate with each other, the electrons at low temperature can form pairs. These pairs act like particles and are so gregarious that they can enter into a single unified quantum state.

In this state the electron pairs are no longer just a current, but a "supercurrent." This supercurrent flows without dissipating energy. It flows without resistance. The practical benefit is that energy loss through dissipation can be eliminated. An additional feature is that much higher currents can flow through some superconductor materials than through normal metal wires. The price to pay for producing the weird quantum state of superconductivity in the first place is having to chill the material down to temperature close to absolute zero, which usually means about 4 K.

Practical applications of wire made from superconducting material include medical scanners (this year's Nobel for medicine rewards MRI research; here potent magnetic fields inside the scanner are usually produced with superconducting cables), levitated trains (still at an early state of deployment), and the chilling of some components in cell-phone networks.

In some superconductors (type I) magnetic fields are anathema to the superconducting state. In other superconductors (type II), magnetic fields are tolerated, and this makes possible the applications just mentioned. Abrikosov and Ginzburg are being recognized for their work in explaining how type II superconductors work. When a sample of helium-3 atoms is chilled to very low temperature, the atoms (which like electrons in a superconductor, are "fermions," particles reluctant to associate) can pair up, and the pairs in turn may enter into a single quantum state in which (analogous to the loss-less flow of supercurrents in superconductors) the fluid will flow without losing energy via friction.

Just as superconductors have no electrical resistance, so superfluids have no viscosity, and can flow freely. Leggett is being recognized for his work in explaining He-3 superfluidity. Superfluidity also appears in samples of helium-4 atoms (although the superfluid mechanism is much different than in He-3), and possibly in Bose Einstein condensates.

(Some background articles: Physics Today, May 1989, Jul 95, Dec 96, Jan 98, Dec 87, May 96; Scientific American, Dec 77, Nov 60, Dec 76, Nov 88, Jun 90, Jul 82, May 66, Dec 93, Aug 94; Physics World, Feb 2000; Nature,13 Mar 97; Leggett, Review of Modern Physics, 1999; Abrikosov et al., Physical Review, 1 July 1958; also see Nobel website)