Oxford (England) - Under the circumstances most of us are familiar with, electrons carry a negative charge and repel each other. However, scientists discovered in the mid 1950s that electron pairs form a special bond in superconductors, a bond which allows superconductivity to exist at all. It's known as the Cooper Effect. They now believe they're on track to eventually explain why this relationship exists.
Generally speaking, superconductors are materials which conduct electricity with no electrical resistance. There are two basic classes, high and low which equate to different forms of ultra-pure metals and alloys for low-temperature (like Mercury, Lead, Niobium-Tin), and complex copper-based alloys for higher temperatures.
Attaining this state superconducting state requires super-cooling the materials below a specific temperature called Tc. Scientists have known about a type of (what they call) "shimmering superconductivity" for a while, which exists well above the Tc. It can be thought of as isolated pockets of remnant superconductivity, even when the material itself is no longer fully superconductive. They've never been able to examine or carry out experiments on these peculiar remnants, until now.
Experiments carried out at the Argonne Laboratories in Argonne, Illinois, have produced a possible explanation for this phenomena. John Schlueter of Argonne was able to construct a special set of superconducting crystals. These were then analyzed by Moon-Sun Nam, Arzhang Ardavan and Stephen Blundell at Oxford University, who were looking specifically for patterns or fluctuations called The Vortex-Nernst Effect. Their research provided a way to detect if superconducting vortices were present, even when an electrical resistance was present, and then to begin analyzing them.
Their work was carried out on very pure crystals which allowed them to determine the nature of the vortices in ways not previously possible. Their findings are preliminary, but could lead to a better understanding of the Cooper Effect, discovered by Leon Cooper in 1956 when he first observed electron pairing in a Fermi Gas. Their work may ultimately lead to a better understanding of the direct reasons why high- and low-temperature superconductors exist. And if that explanation can be quantified, it is very likely that researchers could begin looking for specific material combinations which would allow very high-temperature superconducting materials to exist. Such a finding would do nothing short of change our world as there are already significant applications for expensive, low-temperature superconducting materials.
Funding for this research is carried out by the Department of Energy's Basic Energy Sciences division of their Material Sciences and Engineering program. Argonne National Laboratory has carried out ground-breaking work on superconductors, materials processing and carries out leading edge research in many scientific disciplines.