Experiments Add Evidence for How Superconducting Materials Work
NEW YORK (AP) _ Recent measurements are consistent with a theory that speeding pairs of electrons are what enable superconducting materials to carry electricity without resistance, researchers reported today.
Other scientists already had found evidence for electron pairing through other means, but ″it’s very nice to have this direct confirmatory measurement,″ said Arthur J. Freeman, physics professor at Northwestern University in Chicago.
Physicist Christopher Muirhead and other researchers at the University of Birmingham in England reported the findings in today’s issue of the British journal Nature.
Unlike ordinary materials, superconductors conduct electricity without losing any to resistance when they are cold enough.
The phenomenon has been in the news lately because researchers have found materials that are superconducting at relatively high temperatures. That may open the door to far more efficient computers, mass transit and power transmission, scientists say.
In ordinary materials, electrons flowing as electricity dissipate energy by scattering. In superconducting materials, the standard theory states, electrons pair off and move without scattering.
The British researchers studied a tiny superconducting ring made from the elements yttrium, barium, copper and oxygen.
They applied varying strengths of magnetic fields to produce electrical currents in the ring, and measured how a magnetic signal given off by that current varied in response to changes in the fields.
They found that rather than varying smoothly, the strength of the magnetic signal jumped from one level to another, as if hopping between steps on a staircase. The difference between the levels was consistent with the idea that pairs of electrons were carrying the superconducting current.