St Louis, Missouri
SUPERCONDUCTIVITY is an impressive quantum trick. But you needn’t be a
magician to pull it off—a very good refrigerator will do. Just cool down
an ordinary slab of tin or lead to an icy few degrees above absolute zero, and
electrons, as if charmed, will suddenly pass through it effortlessly, like
ghosts through walls, without encountering the slightest flicker of electrical
resistance.
The trick works at far higher temperatures too, in any of the strange ceramic
materials known as high-temperature superconductors. When first discovered
around 1985, these materials seemed to offer a direct path to technological
nirvana. Just around the corner, finally, were electrical transmission lines and
microchips that would use virtually no energy, and cheap, powerful
superconducting magnets for enormous particle accelerators, amazingly efficient
motors and medical imaging devices.
And yet with few exceptions, superconductors remain in the research labs. The
optimism (and hype) of the mid-1980s has itself cooled into a sober recognition
that superconductivity presents a serious intellectual challenge.
When a superconductor leaves the safety of the lab and goes forth into the
real world, it faces practical demands—it needs to carry large electrical
currents. When these currents flow, they churn up powerful magnetic fields.
Trouble is, these fields circle back and slip inside the material like
saboteurs, destroying its superconductivity. In an instant, a superconductor
turns itself into a normal conductor, or even a useless insulator. It is this
bitter conflict between superconductivity and self-inflicted magnetism that has
condemned high-temperature superconductors to underachievement.
The good news is that at least everyone now agrees that magnetism is a tricky
beast. Researchers have…
