Hot Time for a Cool Contest

By J. MADELEINE NASH

Paul C.W. Chu is science's version of a champion pole vaulter. Every time he smashes a world record, he just puts the bar a bit higher and goes at it again. It's not just that he's never satisfied with himself; he also knows his many competitors won't let the record stand. What Chu, a University of Houston physicist, and his rivals keep pushing higher and higher is the temperature at % which it's possible to create superconductors --those almost magical materials that allow electricity to flow through them with no resistance whatsoever. When scientists get the temperature high enough, superconductors could, among other wonderful things, make computers more powerful, turn electric cars practical and improve energy efficiency by offering a superior alternative to copper wiring. At stake in this competition is far more gold than the Olympic judges could ever award.

Chu and his colleagues first stunned the research community six years ago by showing that a compound containing the exotic element yttrium could become a superconductor at 98 degrees on the Kelvin scale favored by physicists (that's a not-so-balmy -283 degreesF). That record, broken repeatedly, is now as outdated as the 19-foot pole vault, and last month the contest heated up again. First Chu announced in the journal Nature that a mercury-based compound could superconduct at 153 degreesK (-184 degreesF), a startling 20 degrees higher than the old standard. He got that result by subjecting the material to enormous pressure -- the sort that creates diamonds from carbon. Just a week later, a team of researchers in France and Russia reported in Science that they had hit 157 degreesK (-177 degreesF) with a similar compound. Now Chu says he has pushed the mark up to 164 degreesK (-164 degreesF), though he hasn't published this result. "It's really exciting," he says. "Everything is moving fast, really fast."

Superconductors have already been put to impressive use. They are essential to the powerful electromagnets in the huge particle smashers used by physicists and to the magnets that levitate superfast trains called maglevs and enable them to glide above their tracks. To do the job, however, these superconductors must be kept at very low temperatures (around 4 degreesK) through the use of liquid helium, an expensive and hard-to-handle coolant. The goal of current research is to produce superconductors that can perform their magic at less frigid temperatures that are easier to reach and maintain. What's exciting about the latest mercury compounds, Chu points out, is that they can theoretically do their thing with the help of ordinary coolants like Freon, which circulates in household refrigerators.

Even so, the newest superconductors may have trouble making it out of the lab into commercial products. Their biggest drawback: mercury is extremely toxic. But that doesn't diminish the importance of the discoveries. By * studying the mercury compounds, Chu and other scientists can learn more about what makes molecules become superconductors and how laboratory tricks can help the process along. The research has barely begun, and countless compounds remain to be tested. Chu intends to work his way through the periodic table, looking for promising elements to mix into his superconducting concoctions. What's a likely candidate? Well, says Chu, maybe gold.