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Spring 1987
Georgia Power Perspective

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Superconductivity and the power industry

Superconductivity -- excitement on the horizon
Twenty-year-old graduate student Jim Ashburn and his professor, Dr. Mau-Kuen Wu, had already run this test hundreds of times, glancing occasionally through the half-hour at a computer screen that would show them when the electrical resistance in their sample had disappeared. It was Jan. 29, and they were sitting in a 20-foot-by-20foot laboratory at the University of Alabama in Huntsville, an institution eager to inform you it is not a part of the University of Alabama. Around them in the tiny lab were a tangle of wires and soldering irons, crumpled copies of the period table of elements, and an assortment of computer-generated charts, some covered with crayon scribbles. ("Dr Wu's kids come here sometimes" Ashburn noted.) Suddenly, when the sample was at 98 degrees Kelvin (283 degrees Fahrenheit), the line on the graph measuring electrical transmission shot up.

Their first thought was that something was wrong with the thermometer. They ran down the hall to borrow a cylinder of liquid nitrogen, which boils at 77 degrees K (-321 degrees F – the Kelvin scale measures up from absolute zero) to replace the colder liquid helium they were using. Wu started to test a new sample. Trying to solder under the microscope four wires the size of the mysterious fuzz that appears on navy suits to a sample the size of a pencil lead, Wu's hands shook so much that he almost couldn't do it. It worked again. Ashburn ran upstairs to mix the barium-yttrium-copper oxide again, haunted by the myth of the great scientific discovery that can never be repeated, because the sample had some mysterious impurity. It worked again with the new sample.

Wu called his research colleague, fellow Taiwan native Paul Chu at the University of Houston. Ashburn recalled, "They were speaking Chinese, but I knew one word: ‘Jackpot.’ We left the next day for Houston, to verify the results – and out there we saw exactly what we saw here."

In that laboratory in Huntsville – a lab with one assistant professor, two graduate students and a total annual budget of about $70,000 -- they had won a race in which the runners included research teams at Bell Labs, IBM, Stanford University, Argonne Laboratory, Japan, China and the Soviet Union. It was the race to find a material that was superconductive – showing no electrical resistance – at the temperature of the relatively cheap liquid nitrogen. It's a discovery that has the potential to change every aspect of the use and transmission of electrical power.

Ashburn recalled, "It was a little tough to believe. You say you hope to get science a little closer to the goal. You don't imagine you'll be around when something like this happens, much less that you'll be involved. There were a lot of failures for every success. It could be easy to get discouraged, but it was so important. That's why researchers have been trying to push the temperature up ever since superconductivity was discovered 75 years ago.

"We thought breaking the 77-degree mark (the temperature of liquid nitrogen) was something that would happen a hundred or so years from now. I never imagined it would change so rapidly. Ten years ago, if you got an increase of a tenth of a degree you'd write a paper about it."

About four days later, the researchers submitted a paper on the discovery to Physical Review Letters. "We worked through the night on one occasion. We had to be a little secretive about the compound until the paper was submitted for publication," Ashburn commented.

The crumbly greenish-black compound doesn't look like much, but it caused quite an uproar in the world of physics. "When they put out preprints of the March 2 issue of the Physical Review Letters, in which the paper appeared, they said there were people standing at the door," Ashburn said. The annual meeting of the American Physical Society in March looked more like a crowd waiting for tickets to a rock concert than a serious scientific gathering. Fire marshals had to turn away scientists from a special evening session on the discovery, attended by about 3,800, most of whom stayed until after 3 a.m.

After the paper was published, almost every lab working on superconductivity replicated the results. "Now it's really a race. We have to try to remain in the lead. In the beginning, I don't think anyone would have believed we would be the first. Everyone thought Bell Labs would be first," Wu commented.

Wu, 36, became interested in superconductivity as a graduate student in Taiwan, working on his master's degree. "I read some papers on high temperature superconductivity and I tried some calculations, but I didn't have the proper facilities. In 1977, I decided to come to the U.S. to the University of Houston, where I was lucky enough to meet Dr. Paul Chu, who had started working on superconductivity in 1965-66. I was a graduate assistant under him." In 1984, Wu came to the University of Alabama in Huntsville (UAH) as an assistant professor of physics.

The main effort was to try to find a system to check compounds in which higher-temperature superconductivity might be possible. "We didn't have much success. We picked the oxide compounds in 1979, and there were some interesting results. The main problem was that the temperature was not that high, and we switched to another material. In April, another group reported a result on an oxide compound, observing a possible superconductive transient at 35 K. At that time, not too many people believed they had really seen anything, and not many people began to pursue this angle. However, Paul Chu was interested. The report was published in September 1986, and we saw it in October. We picked report apart and decided it was a true superconductive state at 35 K, higher than the record that had held since 1974," Wu recalled.

In late December, Wu was in Houston and discussed with Chu which direction the research should go. Some lanthanum-bearing copper oxides had a strange pattern when X-rayed and researchers had seen superconducting transitions at higher temperatures, but had not be able to reproduce them. They decided which compounds to try. "We divided the effort. I took some compounds and they took others," Wu said. By chance, compound, which generated the excitement, ended up in Huntsville.

As an undergraduate at UAH, Ashburn changed his major to physics. "My first physics class as a sophomore was under Dr. Wu. He was just setting up his lab and I was looking for a job. We were doing materials processing at low gravity, working with NASA." He's worked with Wu ever since. The low-gravity research has been on the back burner sine the Houston researchers asked Wu and his two graduate students, Ashburn and 27-year-old C. J. Torng, another Taiwan native, to get involved. Ashburn was scheduled to take his comprehensive examinations for his master's degree this spring, but said that all the excitement has made studying a bit difficult. "I had been worried about what I was going to write a dissertation about, but I think I know now," he commented.

The next big jump for superconductivity would be room-temperature superconductivity, a discovery that would probably result in as much change as transistors and microchips. "'W can't rule out the possibility or room-temperature superconductivity," Wu said. "On several occasions, especially in Houston, we saw a suggestion of a transition very near room temperature."

This optimism stems, in part, from the fact that superconductivity at 98 degrees K with such a compound is already at odds with the most commonly accepted theory about the way superconductivity works. Theoretically, then, there's no limit to the temperature at which superconductivity can be created, if only the right compounds are discovered. In fact, since January, other labs have reported higher temperatures.

Wu's main focus now is to understand why this material is superconductive at this temperature. "When we understand the mechanism really well, we should be able to go on to higher temperatures." The other part of the research effort is to continue trying to find compounds that are superconducting at higher temperatures. "There are so many possible combinations. That's why it's important to understand what's going on, because it's not possible to try every combination." It's generally believed there's a Nobel Prize waiting for whoever comes up with the theory explaining these results – and hundreds of theorists are already at work.

Ashburn added, "We can make some guesses at what's important in this compound, but we don't understand the mechanism. It wasn't until the mid to late '70s that oxide compounds were even tried in superconductivity experiments. Oxide usually means a poor conductor – rust on iron, for example. But the oxide is somehow critical.

"Yttrium is used in ceramics, barium is a compound with unpleasant medical implications, and you know about copper. They're common enough. We've tried much more rare things. We even tried gold and silver. We're happy they didn't work, because that would limit how the material could be used. We were lucky. It's a cheap material and easy to make – not much different from making a brick. If it hadn't been simple, UAH might not have been the first. That's good, because it's the kind of thing a lot of university labs will be equipped to do. I expect over the next year to see a lot of advances, because so many people will able to work on it."

Superconductivity and the power industry
Dr. Mario Rabinowitz of the Electric Power Research Institute has specialized in superconductivity for 20 years – and has never seen so much excitement. "All of us are fortunate that in our lifetimes, we’ve seen three major inventions – the transistor, the laser and now higher-temperature superconductivity. Two have had a major impact on society, and one will. I can say that it’s not just yesterday’s dream made real, but yesterday’s science fiction made today’s hard science."