Cutting edge: David Caplin

April 27, 2001

The discovery of a new superconductor leads to sleepless nights in Seattle and a surfing frenzy in Los Alamos.

Superconductivity is one of nature's more exotic phenomena - perpetual motion in action. That currents can circulate indefinitely is not just a laboratory trick - it underlies medical magnetic resonance imaging, where strong magnetic fields are generated by coils of superconducting wire, carrying thousands of amperes without resistance.

Only when cooled close to absolute zero (-3C or 0K) do some materials become superconducting. New families of superconductor, discovered 15 years ago, work at 77 degrees above absolute zero, but they are extremely awkward and expensive to fabricate.

Claims of new species of superconductor are like Yeti sightings - rare and difficult to corroborate. But at the beginning of the year rumours began to circulate that a Japanese group had found a simple compound - magnesium diboride, or MgB2 - that was superconducting near 40K (-233C). Corroboration took no more than a phone call to the chemistry department stores and a few minutes to check the powder's magnetic signal. No tricks, no fuss - MgB2 is a robust superconductor.

So what next? Over lunch, half a dozen of us came up with a couple of ideas. After some arithmetic on a paper napkin, I was sceptical - our equipment would not be sensitive enough. Fortunately, our senior postdoc ignored me and returned a couple of hours later with beautiful data - I had lost a few powers of ten in my scribbling. We shifted into high gear. We needed two or three days to take the data and complete the analysis. There was the germ of an interesting paper, suggesting MgB2 could become a much more useful superconductor when a little less pure.

With hindsight, it was a pretty obvious experiment, which prompted fears that we might be beaten to the publication post. I had qualms about the race, but with the research assessment exercise always near the top of the head of department's agenda and this paper likely to be frequently cited. Also, the adrenaline was flowing.

Nowadays, it is not just the paper publication that counts but also a listing on the electronic preprint archive at the Los Alamos National Laboratory ( http:/// - beating bombs into bibliographies, perhaps Aldermaston could emulate). The archive is where physicists and mathematicians post their results without the delay of peer review. This rapid dissemination of science makes it worth checking a few times a day for the latest research - the Chinese papers usually appear by late morning, the American ones in the afternoon or evening.

A hard weekend's work, a tenth draft of the paper and it was ready to send. We seemed to be the first to submit a paper on this aspect of MgB2's behaviour ( Nature , March 29).

Meanwhile, a special session of the American Physical Society's March meeting was announced. Two of us headed to Seattle as hard facts and tenuous rumour were useful. We were still unsure whether we should say anything about our latest idea. The first results were encouraging, but no more. However, a fax showing new data taken over the weekend in London looked impressive - email consultations on what we should say followed. At 8pm on Monday the session began. More than 1,000 physicists crammed into the largest meeting room; and at about 1am, we got the 73rd two-minute slot.

A month later, the science has reverted to a more routine pace. We are making steady progress in understanding MgB2 and its behaviour, with none of the frustrating obstacles nature so often interposes. But I had better just check the Los Alamos website.

David Caplin is director of the Centre for High Temperature Superconductivity at Imperial College of Science, Technology and Medicine.

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