AsianScientist (Jun. 25, 2012) – Japanese and U.S. physicists have discovered new details regarding the intriguing similarities between the quirky electronic properties of a new iron-based high-temperature superconductor (HTS) and its copper-based cousins.
The study, published this week in Nature, offers new clues to scientists studying the mystery of high-temperature superconductivity, one of physics’ greatest unsolved mysteries.
Superconductivity occurs when electrons form a quantum state that allows them to flow freely through a material without electrical resistance. The phenomenon occurs at extremely cold temperatures, almost always below the temperature of liquid nitrogen (minus 196 degrees Celsius), making such superconducting compounds unsuitable for industrial applications.
However, two families of layered metal compounds — one based on copper and the other on iron — achieve superconductivity just short of or above the temperature of liquid nitrogen.
Despite more than 25 years of research, scientists are still debating what causes this phenomenon known as high-temperature superconductivity.
One feature that has been found in both compounds is electronic asymmetry — properties like resistance and conductivity are different when measured up and down rather than side to side. This asymmetry, which physicists call nematicity, has previously been found in both copper-based and iron-based high-temperature superconductors, and the new study provides the strongest evidence yet of electronic nematicity in HTSs.
While investigating a newly-discovered iron-based HTS, the researchers found that its electronic properties were different in the horizontal and vertical directions. This electronic asymmetry was measured across a wide range of temperatures, including those where the material is a superconductor.
“With this new evidence, it is clear that the nematicity exists all the way into the superconducting region and not just in the vicinity of the magnetic phase, as it had been previously understood,” said study co-author Andriy Nevidomskyy, a theoretical physicist.
The researchers believe that their results could help physicists determine whether electronic nematicity is essential for HTS.
The article can be found at: Kasahara S et al. (2012) Electronic nematicity above the structural and superconducting transition in BaFe2(As1−xPx)2.
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Source: Rice University; Photo: Shigeru Kasahara/Kyoto University.
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