Attracting superconductivity

Superconducting wires are used in magnetic resonance imaging machines, high-speed magnetic-levitation trains, and in sensitive devices that detect variations in the magnetic field of a brain. Eventually, ultra-narrow superconducting wires might be used in power lines designed to carry electrical energy long distances with little loss.

Now, researchers at the University of Illinois at Urbana-Champaign not only have discovered an unusual phenomenon in which ultra-narrow wires show enhanced superconductivity when exposed to strong magnetic fields, they have also developed a theory to explain it.

Magnetic fields are generally observed to suppress a material’s ability to exhibit superconductivity – the ability of materials to carry electrical current without any resistance at low enough temperatures. Deviations from this convention have been observed, but there is no commonly accepted explanation for these exceptions, although several ideas have been proposed.

As reported in the September 29 issue of Physical Review Letters, U. of I. physics professor Alexey Bezryadin and his research group have studied the effect of applying a magnetic field to ultra-narrow superconducting wires only a few hundred atoms across, and have used a microscopic theory proposed by physics professor Paul Goldbart and his team to explain the results.