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Superconductivity does the twist; electron dance explains loss of resistance in exotic material.

Sometimes a twist might be as good as a jiggle. Or at least, a new study suggests, twisting electrons appear to take the place of jiggling ions in an exotic kind of superconductor.

It's the first experiment to show that a type of twisting fluctuations by the material's electrons could explain its superconductivity, scientists report in the Nov. 20 Nature. The research also supports a 20-year-old theory about how such twists in electron spin axes could enable superconductivity for some materials.

In superconductors, electric current flows with zero resistance, so a current in a loop of superconducting wire would flow forever even without a power source. Standard superconductors must be kept extremely cold, to almost absolute zero (-273[degrees]Celsius). But some materials are superconducting at transition temperatures as high as about -110[degrees]C, making them cheaper and more practical.

"This work can probably be a foundation for better understanding high-temperature superconductors and can lead to new forms of unconventional superconductivity," says Tuson Park, coauthor of the study and a condensed matter physicist at Los Alamos National Laboratory in New Mexico.

The mechanism that allows electrons to move unfettered through conventional superconductors is well understood. But unconventional superconductors are still poorly understood. Discovering how such materials work is "the holy grail of super-conducting research because only unconventional superconductors can have high transition temperatures," comments Qimiao Si, a condensed matter theorist at Rice University in Houston.

Park and colleagues cooled an exotic material containing the elements cerium, rhodium and indium to near absolute zero, so the material could experience a proposed transition called the local quantum critical point. Around that point, the spin axes of the electrons should begin twisting and fluctuating wildly.

These fluctuations could help electrons to pair up. Only pairs of electrons can move through a superconductor with zero inhibition, but electrons naturally repel each other because they have the same negative electric charge. In conventional superconductors, the jiggling of atomic nuclei in response to the movement of one electron helps another electron to follow closely behind, providing a kind of quantum glue.

"The idea is similar to the conventional except that the glue is different," Park says. Fluctuations in the electron spin axes appear to provide the glue.

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Title Annotation:Matter & Energy
Author:Barry, Patrick
Publication:Science News
Geographic Code:1USA
Date:Dec 20, 2008
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