High-temperature superconductor 'pseudogap' imaged
Date: Thursday, September 25, 2008 @ 22:46:53 UTC
Topic: Science
 By Bill Steele, Physics: Image: With the right combination of temperature (right scale) and percentage
of doping (bottom scale), a cuprate crystal becomes superconducting
(dark blue curve). As the percentage of doping decreases, a scanning
tunneling microscope image reveals some electrons flowing as waves
(shown in a Fourier diagram at lower left) and more and more electrons
locked in place in the crystal lattice (image at upper left). This
finding points the way toward higher-temperature superconductors,
researchers say. Image: Davis Lab
(PhysOrg.com) -- Cornell researchers and colleagues have produced the
first atomic-scale description of what electrons are doing in the
mysterious "pseudogap" in high-temperature superconductors.
Materials known as cuprates,
made of copper oxide doped with other atoms, can become superconducting
with just the right amount of doping, which allows electrons to bind
into pairs that can conduct electricity without interference.
"Pseudogap" refers to the fact that at some levels of doping an energy
signal for these "Cooper pairs" is found, yet the material does not
superconduct. Now Cornell experimenters find that in this state
electrons may pair up, but most of the pairs are locked into fixed
locations in the crystal lattice.
"These are the experimental observations," said J.C. Séamus Davis,
the J.G. White Distinguished Professor of Physical Sciences at Cornell
and a senior scientist at Brookhaven. "Now it's up to the theorists to
explain why it's this way." Davis and colleagues at the Brookhaven
National Laboratory and in Japan report the work in the Aug. 28 issue
of the journal Nature.
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More: http://www.physorg.com/news141320422.html
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