Mar. 19, 2002 A potential new high-temperature superconductor has been identified by physicists at the University of California, Davis. Calculations by Helge Rosner, Alexander Kitaigorodsky and Warren Pickett predict that lithium borocarbide should have essentially no resistance to electrical current at temperatures up to minus 280 F.
Superconductors are used to make very powerful magnets, for example for use in medical magnetic resonance imaging (MRI) machines. They usually need to be cooled to almost absolute zero (minus 450 F) to work. Last year, Japanese scientists found that magnesium diboride, a cheap, readily available material, is a superconductor at minus 389 F, setting off a flurry of research.
Like magnesium diboride, lithium borocarbide is made up of layers of different atoms. Normally, it's a good insulator, but the UC Davis researchers predict that with the right treatment, it should be a superconductor at up to 100 Kelvin (minus 280 F).
The researchers propose using "field-effect doping" to modify the material. Engineers routinely use chemicals to "dope" silicon to make semiconductors. Field-effect doping uses a powerful electric field to force electrons to pile up in the first few layers of the lithium borocarbide structure. Under the right conditions, these electrons would become superconducting.
"Hole-doped lithium borocarbide should be a terrific superconductor, almost certainly better than magnesium diboride," said Pickett. Lithium borocarbide is the first serious candidate in the new class of superconductors related to magnesium diboride, he said.
The results are to be published in Physics Review Letters. Details will also be presented at the American Physical Society meeting in Indianapolis, Ind., March 18-22.
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