The challenge is that superconducting materials must be very, very cold. Even so-called high-temperature superconductors--discovered in the mid-1980s--must be chilled to a "transition temperature" of around �F before they exhibit their amazing behavior. In addition, a full scientific explanation is missing of how high-temperature superconductors work.
The team used the DCA++ application within a promising mathematical framework known as the two-dimensional Hubbard model. These simulations were the first in which it had enough computing power to move beyond ideal, perfectly ordered materials. By looking at materials with disorder--or impurities--the team is moving toward the necessarily imperfect materials found in the real world.
"The real materials are very inhomogeneous," noted team member Thomas Maier of ORNL.
Specifically, the team focused on chemical disorder in high-temperature superconductors known as cuprates--layers of copper oxide separated by layers of an insulating material. By advancing our understanding of the interplay between these imperfections and superconductivity, the work promises to help researchers push transition temperatures ever higher, possibly approaching the lofty goal of "room-temperature superconductors," or materials that exhibit this behavior without artificial cooling.
The team studied the local repulsion between electrons on the same atom. Because electrons have a negative electrical charge, they push one another away in what is known as a Coulomb repulsion. For the material to become superconducting, however, the electrons must overcome this repulsion and join into units called Cooper pairs. The team is looking to take advantage of an earlier discovery that indicates the insulating material promotes this process by drawing electrons away from the
|Contact: Leo Williams|
DOE/Oak Ridge National Laboratory