February 16, 2010

Quebec Physicist Talks Confidently of Reaching Room Temperature Superconductors

Physics professor Louis Taillefer's findings reduce theories explaining high-temperature superconductivity from dozens to only a few.

Taillefer, who collaborated with University of British Columbia scientists, published the team's most recent findings on high-temperature superconductivity in prestigious science journal Nature on Thursday.

They explain the "pseudo-gap" phase, when copper oxides are cooled to minus-100C, and the electrons move in the same direction, enabling electricity to flow flawlessly.

The holy grail of the field would be superconduction at room temperature, Taillefer said. "Now we're pretty sure we know how to get there."

Achieving that would mean MRIs could be much smaller, even portable, since they would not need large and hugely expensive cooling systems. Five times more electricity could be transmitted in the space now required for standard transmission lines.

"This is our next challenge," Taillefer said. "We will try to figure out what's behind the magic with superconductors" at warmer and room temperatures.

Nature - Broken rotational symmetry in the pseudogap phase of a high-Tc superconductor

The nature of the pseudogap phase is a central problem in the effort to understand the high-transition-temperature (high-T c) copper oxide superconductors1. A fundamental question is what symmetries are broken when the pseudogap phase sets in, which occurs when the temperature decreases below a value T*. There is evidence from measurements of both polarized neutron diffraction and the polar Kerr effect that time-reversal symmetry is broken, but at temperatures that differ significantly from one another. Broken rotational symmetry was detected from both resistivity measurements and inelastic neutron scattering at low doping, and from scanning tunnelling spectroscopy at low temperature, but showed no clear relation to T*. Here we report the observation of a large in-plane anisotropy of the Nernst effect in YBa2Cu3Oy that sets in precisely at T* throughout the doping phase diagram. We show that the CuO chains of the orthorhombic lattice are not responsible for this anisotropy, which is therefore an intrinsic property of the CuO2 planes. We conclude that the pseudogap phase is an electronic state that strongly breaks four-fold rotational symmetry. This narrows the range of possible states considerably, pointing to stripe or nematic order

18 page pdfs supplemental information

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