Slusky catches Cava's enthusiasm for research on super conductors
Steven Schultz
Princeton NJ -- Bob Cava knows superconducting. Not just the kind that happens when very cold materials lose all resistance to carrying electricity. He knows how to convey the electricity of scientific discovery, unabated, to his students.
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Senior Joanna Slusky (left) was part of a research group that, working under Professor of Chemistry Bob Cava, led a worldwide race to understand a newly discovered superconducting material. In an unusual achievement for an undergraduate, she was a co-author on several papers in the journals Nature and Science.
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"I told them if they wanted to make an impact, now was the time to do it and it was us against the entire world," said Cava.
It was a Friday afternoon. Lab members ditched their weekend plans. For the next few weeks, they worked late into the night, investigating the material and producing the first insights into its unusual properties. By the end of May, the group, collaborating with scientists around the world, had published three articles in the journal Nature, one in Science and many more in other journals.
This fast pace of discovery -- unusual by nearly any standard in science -- was made all the more remarkable because one member of the research group was an undergraduate. Joanna Slusky, a senior chemistry major, was a co-author on most of the articles and was the lead author -- meaning she conducted the principal experiments -- on one of the Nature papers.
"It was a really intense period, and it was really exciting," said Slusky.
"To me, it was what a scientist would always dream about. As a person who really enjoys science, I can't imagine anything more exciting than what was going on then."
As news of the discovery became widely known, the students realized they were helping to fuel an international race. One day, they listened as Cava was interviewed about the developments on National Public Radio. "It was exciting to be next to the radio and thinking 'Wow, this is what we did and we're on national radio,'" said Kim Regan, a second-year graduate student.
The tip of an iceberg?
Ever since a Dutch physicist discovered it in 1911, superconductivity has been an important research area. The first superconductors were materials that lost all electrical resistance when cooled to just a few degrees above absolute zero. For decades, scientists concocted ever more complicated compounds looking for superconductivity at higher temperatures, but seemed stuck at about minus 250 degrees Celsius. That changed in 1986 when materials were discovered that became superconductors above minus 200 degrees, the temperature of the commonly available coolant liquid nitrogen. In many respects, however, these high-temperature superconductors turned out to be harder to make and use than the low-temperature materials -- and so the search for the perfect superconductor continues.
The news Cava heard from Japan that day in January was that a very simple compound, readily available from chemical supply companies, had been overlooked and was a superconductor. The compound, called magnesium boride, did not set a new record -- its "critical temperature" is minus 234 degrees -- but it did possess many positive aspects of the low-temperature superconductors. In addition, magnesium boride is very inexpensive, and its critical temperature is just high enough that it can be cooled by an electric refrigerator instead of a very elaborate liquid helium system.
Potential applications include magnetic resonance imaging (MRI) devices, which currently rely on liquid helium to cool superconducting magnets, or such futuristic technologies as levitating trains.
Cava knew that the days after finding out about the new material would be critical. He predicted that the initial discovery was just the "tip of an iceberg" that may yield important insights into the science and technology of superconductors.
Passionate about science
The race for fast answers was not new to Cava. As a scientist at Bell Labs in the 1980s, he was part of the group that led the discovery of high-temperature superconductors. In the intervening years, he has become an international authority on superconductivity and holds many patents on superconducting materials. But his expertise hasn't dimmed his enthusiasm.
"I remember that first meeting -- his whole face just lit up when he was talking about the discovery," said Regan.
"Professor Cava is so passionate about science -- you can't help but catch it," said Slusky. "It's really contagious."
But the days weren't easy. That first Friday, graduate student Nyrissa Rogado was in the lab past midnight synthesizing the first samples of magnesium boride. And from then on, the students and Cava were in the lab from early morning until late at night.
"We had eight weeks of really, really hard work, but we got a lot out of it," said Regan, who is planning to follow-up on the magnesium boride work for her doctoral thesis.
"It really taught us about the timescale of doing this kind of science," said graduate student Mary Haas. "In some cases, if we had taken just a couple days longer others would have beaten us to the punch."
The group held daily meetings to map out the strategy for their experiments. After confirming the reported result, they began making hundreds of magnesium boride samples to send to collaborators at labs around the world for specialized testing. Often the samples were taken directly out of the furnace where they were baked at 900 degrees and dropped into FedEx packages. "We had some really hilarious scenes," said Cava. "Eventually, the FedEx guy knew to come around to the side door (near the furnace)."
One priority was to try adding other elements to magnesium boride and observing the effects. "We took the periodic table and divided it up among the students," said Cava. Slusky's assignment was aluminum. When she succeeded in combining magnesium boride and aluminum, the compound ceased being a superconductor. The result was not particularly interesting, but Cava had a hunch that further tests would reveal important information about how the compound's superconductivity depended on its chemical structure.
Cava knew that the retesting would be very time-consuming and there was a great risk of finding nothing. Slusky tackled the work and discovered that when she added enough aluminum to stop the superconductivity, the crystal structure of the compound collapsed. The result appeared in the March 15 issue of Nature.
"It remains the most interesting piece of chemistry that has been done on magnesium boride," said Cava. "Months later, after everyone's tried, no one has done anything like it."
"During a real down part, she stuck with me and really made it work," he said.
Indeed Cava credits all the lab members with turning out first-rate work under great pressure.
"It was an ordeal," said Cava, "but they got a real taste
of the thrill of being in on something from the very, very
beginning."
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June 4, 2001 Contents Commencement
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