Resistance is useless: The lure of superconductors
PARIS (AFP) Oct 07, 2003
Imagine a world where trains, levitated and propelled by magnets, take just an hour to glide sleekly between Boston and Washington.

Where a PC will have as much power as a supercomputer today.

And where global warming, caused by the inefficient burning of fossil fuels, was a distant scare story of the early 21st century.

This is the sci-fi allure of superconductors, the tantalising materials of the future that on Tuesday earned the 2003 Nobel Physics Prize for two Russian-born quantum researchers, Alexei A. Abrikosov and Vitaly L. Ginzburg.

The pair share the award with a British-born American, Anthony J. Leggett, for his research into the intriguing and still unresolved phenomenon known as superfluidity.

If daunting technical challenges can be overcome, superconductors could revolutionise human life almost as much as the advent of electricity itself.

They are materials that, at very cold temperatures, allow electricity to flow through them without offering any resistance or dissipating any of the energy as heat.

Electricity introduced into a closed superconductive circuit will simply keep flowing endlessly -- the closest thing to perpetual motion.

The phenomenon was discovered in 1911, when Dutch physicist Heike Kamerlingh Onnes cooled mercury to just above absolute zero (O Kelvin, -273 C, and found resistance in the ultra-cool liquid metal abruptly disappeared.

It took two generations of scientists to lay the conceptual groundwork for explaining this, including Abrikosov's and Ginzburg's work during the 1950s, during the golden age of Soviet physics, which exposed the link between superconductivity and magnetism.

And it took a breakthrough in materials science in the mid-1980s for what was until then a quirk of science to be hauled out of the lab and into the realm of applications.

Although there remain many things to explain, the theory is this: in superconductive materials that are cooled to below their transitional temperature, negatively-charged electrons known as Cooper pairs are suddenly coupled together.

These pairs act as "carriers" for electrical current, overcoming impurities and so-called lattice vibrations in a solid that can scatter and shake up electrons and thus cause heat and resistance.

So superconductive cables and dynamos would be many more times efficient than copper and other conventional conductors. They would be a boon for combatting climate change, because fossil-burning power stations would only need to burn a fraction of today's fuel to get the same yield to the consumer.

And superconductor computers could be much faster than today's, because in addition to being resistance-free, their processors would not be hampered by heat, one of the biggest problems facing designers today who try to crowd ever more circuits onto a chip.

The race, therefore, is on to find materials that do not have to be handled in laboratory conditions, in which they have to be chilled to ultra-cold temperatures to achieve superconductivity.

An early breakthrough came in 1986, with the discovery of metal oxides that achieved a transition temperature of about 30 Kelvin (-243 C, -405.4 F).

Further experiments, using exotic oxides cooled by liquid nitrogen, which is plentiful and cheap, have yielded transition temperatures as high as 160 Kelvin (-113 C, -171.4 F).

These advances -- while still far above anything that can operate even close to room temperature -- have been enough to catapult superconductive substances into specialist applications.

They include superconductive magnets that exert a highly powerful, localised magnetic field.

These magnets can be found in magnetic resonance imaging, the scanner technology that on Monday earned the 2003 Nobel Prize for Medicine. And they are being incorporated into the world's biggest atom-smashing facility, being built by European particle physicists at CERN, Switzerland.