Resistance Movement : Breakthroughs in Electrical Superconductors Have Scientists Charged Up
These days when the telephone perforates the silence of M. Brian Maple’s office in the physics building at UC San Diego, chances are good that someone is calling with a hot rumor off the sizzling grapevine of solid-state physics.
Flanked by pictures of Einstein and a bolt of lightning, Maple swivels in his chair and listens to the murmurings on the line--long-distance dispatches from the front lines of a revolution in physics in which Maple plays a key part.
“There’s been this report . . .,” the soft-spoken professor relates with some amusement to a visitor. “It hasn’t been substantiated by anybody. . . . This rumor says that somebody’s going to have a press conference tomorrow. I don’t know what this means.”
M. Brian Maple heads one of several dozen labs embroiled in a remarkable revolution in the field of superconductors, materials that have long fascinated physicists because of their ability to conduct electricity without resistance.
Late last year, Swiss researchers broke a 14-year stalemate in the field by concocting new materials that become superconducting at record high temperatures. The achievement set off a stunning series of breakthroughs. Barriers began tumbling like dominoes.
Until then, superconductivity had been achieved only at hundreds of degrees below zero Fahrenheit. Because that required cooling with liquid helium, superconductors remained too expensive and unfeasible for everyday applications.
But the Swiss discovery suggested some materials might become superconductors at warmer temperatures, achievable with cheaper liquid nitrogen. As the ceiling soared, people began to speculate about superconductivity at room temperature.
The recent advances have left scientists and businessmen besotted. There is heady talk of super-fast computers, light-weight car engines and superconducting transmission lines. In Japan, there are experiments with high-speed trains that levitate above the tracks.
“This achievement was so unexpected that I think it just shocked everybody, and everybody wanted to be a part of it,” Maple said in a recent interview. “It just made all of these things that people have been dreaming about that much more feasible and attractive.”
Since January, Maple and a phalanx of graduate students and post-doctoral fellows have toiled day and night in Maple’s lab beneath the physics building at UCSD, where the 47-year-old professor has spent his adult life exploring superconductivity.
There, they cook up combinations of oxides of metals, “prospecting” for better superconductors. Their materials include mixtures of elements like yttrium, barium, copper and rare earth elements, compressed and fired at 1,000 degrees of heat.
“Well, I suppose it’s like trying to discover America, or something like that,” he ruminated, when asked why the insomniac rush to be first. “I mean, to think that you are the first person or the first group to go into a laboratory and observe something.
“And it’s something you can’t really depend upon, there’s no way to prepare for it. The only thing you can do is work very hard and hope you have good intuition. I don’t think most people are motivated by financial reward. Or else we wouldn’t be university professors.”
The Search
Superconductivity occurs in certain materials when they are cooled to their so-called transition temperature. Until late last year, the highest transition temperature ever observed was several hundred degrees below zero Fahrenheit.
“The first thing that happens--the most spectacular, I suppose--is (the material) loses all of its electrical resistance,” Maple said. “If you pass an electrical current through a wire in the superconducting state, (it) flows through without any loss of energy whatsoever.”
Normally, a current passing through a material encounters resistance, generating heat and resulting in a loss of energy. Depending on the conditions, Maple said, as much as 20% to 30% of energy might be lost in passing a current through a wire.
That loss occurs in part because electrons moving through the metal are colliding with impurities and imperfections, Maple said. But in the superconducting state, the electrons seem to act in a kind of unison known as a “cooperative phenomenon.”
“So that’s a very special state of matter, and of course it is very fascinating because of that law,” Maple said.
Since 1973, the highest transition temperature ever observed had remained stuck at 23 Kelvins. On the Kelvin scale, where zero is minus 459 degrees Fahrenheit and 300 is room temperature, 23 Kelvins is hundreds of degrees below zero Fahrenheit.
Some physicists had begun to wonder whether they had hit a natural ceiling.
Then late last year, a group of researchers with IBM in Switzerland reported signs of superconductivity at 30 Kelvins in a new compound. Because of the nature of the material and the cautiously reported findings, other physicists remained skeptical.
“A lot of us were--what’s the proper word?--desensitized to these kinds of reports,” recalled Maple. “Because (over the years) we’d seen a series of things that could not be verified or reproduced.”
But a group at the University of Tokyo quickly followed up with experiments that seemed to confirm the Swiss findings. Then researchers at the University of Houston applied pressure to the new material and raised the transition temperature even further.
By early this year, labs across the United States had become involved, including labs at UCSD and Stanford that had worked with superconductivity for years. In addition to the work in Japan, reports were filtering out of China.
Opening the Door
“I mean, if it was really true, then obviously it was very important,” Maple said. “And it’s the sort of thing you almost couldn’t not work on. You just had to. Because you know, who knows where it’s going to go? We still don’t know how far it’s going to go.”
In February, researchers in Houston and Alabama announced evidence of superconductivity at 90 Kelvins in a compound of yttrium, barium, copper and oxygen. They had broken into “liquid nitrogen temperatures,” opening the door for the first time to widespread applications.
Since then, a number of labs, including Maple’s, have pushed the ceiling further to 97 or 100. And late last month, physicists at Wayne State University announced they had seen evidence of superconductivity at 240 Kelvins, or 27 degrees below zero Fahrenheit.
“It’s sort of put a new perspective on what ‘recently’ means,” mused Maple. “Recently used to mean, at least to me, six months ago or last year or a year and a half ago. Now it means three days ago.”
Last month in New York City, Maple convened a remarkable special session on the new developments at the annual meeting of the American Physical Society’s condensed matter division, of which he is chairman. Pulled together at the last minute, the session drew an unprecedented 3,800 scientists, many of whom stayed up all night in what has been dubbed “the Woodstock of physics.”
As late as November, when Maple and others were planning the annual meeting, no papers had been submitted on on the subject. But in December and January, as labs began reporting their findings, it was decided to convene the special session.
Calls began pouring in with requests to present papers. There would have been no way to decide quickly which ones to accept. So Maple and the other organizers settled on allowing just five minutes for every person who chose to speak.
“And so, time passed and we would get more and more of these calls,” Maple said. “So we’d add more and more people to the program. Then we got really scared, because it was growing by leaps and bounds.”
The meeting was set for the New York Hilton. Unfortunately, the grand ballroom was reserved for something else. The largest room Maple could get held 1,000, so the organizers arranged for video cameras in the rear, in the halls, and in the anteroom.
The night of the meeting, the entire area was packed.
“We were very worried because it was just a mass of people in there, and this is also a very competitive and emotionally charged subject,” Maple said. “So we kind of wondered whether we could keep this under control.”
The program began at 7:30 p.m. Presentations were held to 5 minutes each, with 10-minute discussion periods interspersed. The program wrapped up at 3:15 a.m., with several hundred people left. Many stayed up past dawn, talking.
“Some people say, ‘Well, maybe it’s like (the discovery of) the transistor,’ ” Maple said. “But I think not, in the sense that the transistor really opened up things that weren’t even envisaged at the time. Here, the applications of superconductivity are well known. But it’s something that is not generally known to the public, for some reason that I don’t quite understand.”
One of the more significant applications of superconductivity is in producing large magnetic fields, because the other basic property of a superconductor is that it expels from its interior a magnetic field.
Such fields can be used in laboratory research, mineral separation and in magnetic resonance imaging. Other applications include controlling the trajectory of charged particles in high-energy accelerators in controlled nuclear fusion for production of energy.
Another potential application is energy storage in superconducting solenoids, in which a wire is wound around a form like a cylinder. A current can be sent into the wire, the two ends of the wire attached, and the energy stored indefinitely with no loss.
Finally, there is talk of superconducting motors and generators in which superconducting wires replace ordinary wires. Because they would be lighter and more efficient than conventional versions, Maple said the Navy has expressed interest in using them on ships.
For the time being, the new materials capable of superconductivity are brittle ceramics that will have to be made into flexible wires before they can be used widely. Maple said they also must be improved to allow transmission of stronger currents.
But Maple, for one, is cautiously optimistic.
“This could be the very beginning,” he said. “That’s what’s so incredible about it.”
