Despite their name, "high temperature" electrical superconductors actually require quite low
temperatures by normal standards to work -- the highest around minus-211 degrees Fahrenheit.
At that temperature an electrical current flowing in a loop of superconducting wire would whip
around forever with no additional power source because the superconductor has no electrical
resistance.
For the past 50 years scientists have had a model that successfully explained
superconductivity and how it reacts in a magnetic field. Until now. A recent discovery by an
international team of researchers led by Notre Dame physicist Morten Ring Eskildsen is causing
physicists to rethink some of the details of that model.
When a so-called "type II" superconductor is placed in a magnetic field it becomes
"threaded" with incredibly tiny swirling "tornadoes" of electric current arranged in a certain
lattice pattern that penetrates the superconductor, the assistant professor of physics explains.
However when Eskildsen's team, which included scientists from Canada, Switzerland,
the United Kingdom and the United States, measured the "tornado" lattice of a certain exotic
superconductor composed of cerium, cobalt and indium (CeCoIn5) they were surprised to find
that as they increased the magnetic field, the lattice became more pronounced -- in stark contrast
to what is seen in other superconductors and what the model predicts. Usually, increasing the
magnetic field diminishes superconductivity because it increases the number of "tornadoes" in
the superconductor.
"[T]his forces us to rethink our understanding of superconductivity," Eskildsen says. The
"tornadoes" or vortices are of intense theoretical and practical interest because they are the main
limiting factor in a superconductor's ability to carry electric current resistance-free.
Superconductors are used in, among other things, magnetic resonance medical imaging
machines, filters for mobile phone base stations, and magnetic separation in the pigment
industry. The technology also is being developed for various uses in power transmission, electric
motors and magnetic levitation trains. Notre Dame grad student Lisa DeBeer-Schmitt assisted in
the research.
John Monczunsk is an associate editor of this magazine. Email him at monczunski.1@nd.edu.
(April 2008)
