14 DAY TRIAL // Scientists at the Rice University have recently determined that certain types of superconductors are able to carry electrons indefinitely – as in to store electrical energy – only if those electrons have certain magnetic properties. The new discovery, which was made by US and Chinese experts, may help physicists gain new insight into the fundamental nature and characteristics of high-temperature superconductivity, RU experts say.
The study was carried out on a recently discovered class of iron-based superconductors, the team reports in the January 8 issue of the respected scientific journal Physical Review Letters. Scientists believe that superconductors could be used in the near future for a wide array of useful and common applications, such as developing more advanced electric generators, better MRI scanners, high-speed trains, and a host of other devices too.
The team investigated iron-arsenide compounds, which are undoped variants of NICK-tides (pnictides). The second class of materials was discovered to have superconductive abilities just two years ago. “We found the first direct evidence that a magnetic quantum critical point exists in these materials,” Rice physicist Qimiao Si, who has also been a coauthor of the new paper, says. In order to reach this conclusion, the team used the neutron-scattering facilities at the US National Institutes for Standards and Technology (NIST), and the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL).
The work built up on previous researches by Si and his team, which were published in the March, 2009 issue of the respected journal Proceedings of the National Academy of Sciences (PNAS). The experts wrote at the time that modifying the size of atoms in the compounds could grant physicists the ability to fine-tune the material's quantum fluctuations. These phenomena can give birth to “quantum critical points,” which occur when a material is about to transit from one quantum state to another.
“Our finding of a quantum critical point in iron pnictides opens the door for new avenues of research into this important class of materials,” neutron scattering expert Pengcheng Dai, who is also a physicist at the University of Tennessee and the ORNL, explains. “The evidence from this study bolsters the hypothesis that high-temperature superconductivity in the iron pnictides originates from electronic magnetism. This should be contrasted to conventional low-temperature superconductivity, which is caused by ionic vibrations,” Si concludes. The work was made possible through grants from the US National Science Foundation (NSF), and the Robert A. Welch Foundation.