Scientists detect 'fingerprint' of high-temp superconductivity above transition temperature.
Washington, August 28 (ANI): A team of US and Japanese scientists has shown for the first time that the spectroscopic "fingerprint" of high-temperature superconductivity remains intact well above the super chilly temperatures at which these materials carry current with no resistance.
This confirms that certain conditions necessary for superconductivity exist at the warmer temperatures that would make these materials practical for energy-saving applications - if scientists can figure out how to get the current flowing.
"Our measurements give the most definitive spectroscopic evidence that the material we studied is a superconductor, even above the transition temperature, but one without the quantum phase coherence required for current to flow with no resistance," said physicist Seamus Davis of the US Department of Energy's (DOE) Brookhaven National Laboratory and Cornell University, who led the research team.
"The spectroscopic 'fingerprint' confirms that, at these higher temperatures, electrons are pairing up as they must in a superconductor, but for some reason they are not co-operating coherently to carry current," Davis said.
The technique and findings may point the way to identifying what inhibits coherent superconductivity at higher temperatures.
That knowledge, in turn, may help scientists achieve the ultimate goal of developing super-conducting materials for real-world practical devices such as zero-loss power transmission lines.
Using a spectroscopic imaging scanning tunneling microscopy method developed over many years, Davis and his collaborators had previously conducted extensive studies of the superconducting state of a copper-oxide superconductor containing bismuth, strontium, and calcium (known as BSCCO).
These studies identified a detailed spectroscopic signature containing all the quantum mechanical details of that superconducting state.
The new study was designed to see whether the signature changed when the material was warmed above the transition temperature, which is 37 kelvin, or -236 degrees Celsius.
This was a major challenge, however, because the method works best at very cold temperatures.
As materials warm up, electrons start moving around more energetically, decreasing the resolution of the measurements.
"We had to make a series of modifications to greatly increase the signal-to-noise ratio for all measurements," Davis said.
Some measurements were made over a period of up to 10 days. By averaging measurements over those long times, the scientists were better able to isolate a weak signal from the random background noise.
The results were definitive.
"We found that the characteristic signature passes unchanged from the superconducting state into the parent state - up to temperatures of at least 55 K - or 1.5 times the transition temperature," Davis said. (ANI)
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|Publication:||Asian News International|
|Date:||Aug 28, 2009|
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