Scientists at the U.S. Department of Energy’s Brookhaven National Laboratory, in collaboration with researchers at the Rutherford Appleton Laboratory in the United Kingdom and Tohoku University in Japan, have discovered evidence supporting a possible mechanism for high-temperature superconductivity that had previously appeared incompatible with certain experimental observations. The finding, which hinges paradoxically on what the scientists observed in a particular material that loses its superconductivity for a special composition of atoms, is bound to be controversial in this dynamic field. It is described in the June 3, 2004 issue of Nature.
“We definitely expect some controversy,” said Brookhaven physicist John Tranquada, lead author on the paper, “because our data suggest that some popular ideas are wrong.”
The scientists were studying a material composed of lanthanum, barium, copper and oxygen (LBCO). The parent compound, LCO, which lacks the barium, is not a superconductor (a material through which current moves with no resistance), nor even a regular conductor. This is because the repulsive forces between the like-charged electrons on adjacent copper atoms keep them separated and somewhat locked into position – unable to carry a current. In this arrangement, the electrons on adjacent atoms align themselves so that their spins alternate in an up, down, up, down fashion, producing a condition scientists call antiferromagnetism.
Karen McNulty Walsh, | BNL
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