Electrons' 'love-hate' clue to superconductivity (10/10/2007)

The arrangement of molecules inside the molecular superconductor used by Oxford University scientists in their experiments. Credit: Stephen Blundell.

A form of 'shimmering' superconductivity may offer vital clues as to how superconductors work, according to Oxford University scientists.

The 'shimmering' occurs when electrons are caught in two minds about whether they 'love' each other (pairing up to create superconductivity) or 'hate' each other (are repelled, creating insulating behaviour).

In an article in Nature the Oxford team report that, in a molecular superconductor on the borderline between superconducting and insulating behaviour, a slight preference for love over hate can result in a fluctuating state of superconductivity that exists at temperatures 50% higher than that at which ordinary superconductivity is destroyed.

Superconductors are materials that, once cooled to their critical temperature, exhibit zero electrical resistance and resist the penetration of magnetic fields: They are already finding applications in MRI scanners and electrical power technology.

While shimmering superconductivity only occurs at extremely low temperatures (18K-12K) scientists think that understanding it could lead to future breakthroughs in room-temperature superconductors. The Oxford experiment provides hard evidence that the effect exists in bulk superconductors and is not the result of impurities in the materials being studied.

The discovery was made by Dr Moon-Sun Nam working with Dr Arzhang Ardavan and Professor Stephen Blundell of Oxford University's Department of Physics, using samples prepared by Dr John Schlueter at Argonne National Laboratory. The team used a probe that can detect when superconducting vortices are present even when a material does not exhibit zero electrical resistance - the conventional measure of ordinary superconductivity.

'This observation sheds new light on the mechanisms of exotic superconductivity, which have remained elusive despite a number of experimental breakthroughs,' said Dr Ardavan. 'We believe that the fluctuating effect should be found in many superconductors in which the 'love-hate' relationship between electrons is finely balanced. It represents an important step forward in the quest to understand exotic superconductors.'

A report of the research entitled 'Fluctuating superconductivity in organic molecular metals close to the Mott transition' was published in the journal Nature on 4 October 2007.

Note: This story has been adapted from a news release issued by Oxford University

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