New class of unconventional materials

Physicists of MIT have discovered patchwork quilt-like variations at the atomic scale in several high-temperature superconductors. These finding could help scientists understand a new class of unconventional materials.

The variation  known as the Fermi surface, which has never been seen before in any kind of material, could just be an oddity. But it could also serve as an important clue for physicists working to unravel the mystery of why a broad new class of materials exhibits exotic properties from high-temperature superconductivity to colossal magneto-resistance. In strongly correlated electronic materials, interactions between electrons, normally weak enough that they can essentially be ignored, dominate the physics of the material, leading to a host of unexplained phenomena.

Eric Hudson, associate professor of physics said that these materials are so unusual that the researchers decided to check for variations that would normally be impossible -- and there they were. Hudson and colleagues found that the Fermi surface, a measurement of the distribution of electrons in a material, varies at the atomic scale across the surface of two bismuth-based superconductors, which belong to the class of strongly correlated electronic materials. Until now, it was believed that Fermi surface was uniform throughout any material.

The electrons separated by just an atom's distance can behave so differently. The discovery that electronic properties can vary so much on the nanoscale could shed light on how this class of materials deals with strongly interacting electrons, and how their unusual properties arise. To study the Fermi surface, the researchers used scanning tunneling microscopy, combined with a new analysis method called quasiparticle interference.  this technology can reveal, on an atom-by-atom basis, what electrons are doing.


Vasil Sidorov on March 7, 2009 after MIT Tech Talk



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