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May 31, 2007

Two superconductor advances

Tiny, isolated patches of superconductivity exist within these superconducting substances at higher temperatures than previously were known, according to a paper by Princeton scientists, who have developed new techniques to image superconducting behavior at the nanoscale.


Caption: Using a customized microscope, Princeton scientists have mapped the strength of current-carrying electron pairs as they form in a ceramic superconductor. From the top left, the images show the same 30-nanometer square region of the ceramic at successively cooler temperatures. Red areas indicate the presence of superconducting pairs. Even at 10 degrees Celsius above Tc, the temperature at which the entire sample exhibits superconductivity, the electron pairs still exist in localized regions (top left image). Credit: Princeton University/Yazdani labs


The regions are only a few nanometers wide, but they appear in some materials at up to 50 degrees above the critical temperature. Ali Yazdani, senior author of the research paper, said that understanding why these minuscule patches of superconductivity exist at higher temperatures -- and how to create a material that exhibits the property everywhere -- may be the key to enhancing superconductivity.


Another superconductor discovery
A team of University of British Columbia researchers has contributed to the greatest advancement in superconductor research in a decade by "growing" the purest samples of superconductors to date.


"Up to now, it was unclear whether these materials were metals or insulators," said UBC Physics Prof. Douglas Bonn, adding that the materials are extremely sensitive to contamination - the slightest trace of dirt or impurity can alter their properties completely.

"We were able to supply our collaborators with the purest sample ever developed, leading to the discovery of quantum oscillations," said Bonn. "This provides unequivocal proof that these materials are metals."

"The results are crystal clear," said Louis Taillefer. "High-temperature superconductors were discovered in 1987, and only now do we finally have concrete knowledge about their deep nature. This discovery gives both theorists and experimentalists something real to work with.

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