One step closer to superconductors

Call it the 135 K wall. What might sound like the end of a torturous foot race is a temperature barrier (135 degrees Kelvin) that scientists have yet to breach in their quest for new materials that, when properly chilled, carry electricity without any resistance.

Known as superconductors, these materials hold the promise of smaller, faster computers, smaller and more powerful electric motors, and a more reliable and energy-efficient electrical-utility grid. The goal is to push superconductor operating temperatures higher, so they can work without expensive equipment that keeps them chilled at more than 200 degrees below 0 F.

Now, scientists in Colorado report that they have created a new state of matter that could provide insights to help researchers punch through the 135 Kelvin (minus 216.7 degrees F) wall. The team speculates that such insights could lead to materials that conduct electricity without losses at room temperatures. Their work appears in a recent online issue of the journal Physical Review Letters.

"We've opened a door, and where it goes is unclear," says physicist Deborah Jin, who led researchers at JILA, a research institute run by the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.

Still, she adds, the discovery "provides a model system for understanding superconductivity," especially in a class of materials discovered in the late 1980s that breached an earlier, colder temperature barrier.

Even without a potential superconductor connection, "this is an outstanding scientific accomplishment," says Martin Maley, former science director at the Los Alamos National Laboratory's Superconductor Science Center.

The new form of matter is known as a fermionic condensate. It joins a growing list of states of matter that form in the most extreme cold and act in bizarre ways compared with their counterparts at more torrid temperatures. The condensate draws its name from the particles that form it.

Physicists have placed fundamental particles of matter into two broad categories, explains Eric Cornell, an NIST researcher who shared a Nobel prize in 2001 for creating an extremely low-temperature form of matter known as a Bose-Einstein condensate. Fermions - such as electrons, protons, neutrons, and quarks - form the building blocks of matter. Particles called bosons carry forces acting on fermions. Moreover, he adds, bosons can readily be coaxed to congregate, while fermions are loners.

These same "social" characteristics can hold true for atoms. In 1995, Dr. Cornell and colleague Carl Weiman of the University of Colorado in Boulder and, separately, Wolfgang Ketterle of the Massachusetts Institute of Technology, formed a condensate of bosons from tenuous clouds of rubidium and sodium atoms. The clouds were chilled to 20 billionths of a degree above absolute zero. At those temperatures, the atoms - numbering only several thousand - appeared to merge and behave as one collective super atom - a Bose-Einstein condensate.

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