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Despite lack of free electrons, bismuth superconducts

Theoretical questions raised by element’s loss of electrical resistance near absolute zero

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2:00pm, December 1, 2016
bismuth

CONDUCTIVE CRYSTAL  A pure crystal of bismuth, like this cube (right), superconducts below 5 ten-thousandths of a kelvin, scientists report. Impure crystals of bismuth display iridescent patterns due to layers of oxidation that form on their surface (left).

An oddball superconductor is the first of its kind — and if scientists are lucky, its discovery may lead to others.

At a frigid temperature 5 ten-thousandths of a degree above absolute zero, bismuth becomes a superconductor — a material that conducts electricity without resistance — physicists from the Tata Institute of Fundamental Research in Mumbai, India, report online December 1 in Science.

Bismuth, a semimetallic element, conducts electricity less efficiently than an ordinary metal. It is unlike most other known superconductors in that it has very few mobile electrons. Consequently, the prevailing theory of superconductivity doesn’t apply.

The result is “quite important,” says theoretical physicist Marvin Cohen of the University of California, Berkeley. New ideas — either a different theory or a tweak to the standard one — are

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