Paul Chu. Photo: University of Houston.
Paul Chu. Photo: University of Houston.

Researchers at the University of Houston (UH) have reported a new method for inducing superconductivity in non-superconducting materials, demonstrating a concept proposed decades ago but never proven.

This technique could also be used to boost the efficiency of known superconducting materials, suggesting a new way to advance the commercial viability of superconductors, said Paul Chu, chief scientist at the Texas Center for Superconductivity at UH (TcSUH) and corresponding author of a paper on the work in the Proceedings of the National Academy of Sciences.

"Superconductivity is used in many things, of which MRI (magnetic resonance imaging) is perhaps the best known," said Chu. But the technology used in health care and other fields remains costly, in part because it requires expensive cooling, which has limited widespread adoption.

In this work, Chu and his colleagues demonstrate a new method for taking advantage of assembled interfaces to induce superconductivity in the non-superconducting compound calcium iron arsenide, thereby offering a new approach to finding superconductors that work at higher temperatures.

Superconducting materials conduct electric current without resistance, while traditional materials can lose as much as 10% of the energy being transmitted between the generating source and the end user. That means superconductors could allow utility companies to provide more electricity without increasing the amount of fuel used to generate the electricity.

"One way that has long been proposed to achieve enhanced Tcs (critical temperature, or the temperature at which a material becomes superconducting) is to take advantage of artificially or naturally assembled interfaces," the researchers write in the paper. "The present work clearly demonstrates that high Tc superconductivity in the well-known non-superconducting compound CaFe2As2 (calcium iron arsenide) can be induced by antiferromagnetic/metallic layer stacking and provides the most direct evidence to date for the interface-enhanced Tc in this compound."

The concept that superconductivity could be induced or enhanced at the point where two different materials come together – the interface – was first proposed in the 1970s but had never been conclusively demonstrated, Chu said. Some previous experiments showing enhanced Tcs could not exclude the influence of other effects such as stress or chemical doping, which prevented verification, he said.

To validate the concept, researchers working at ambient pressures exposed the undoped calcium iron arsenide compound to a relatively low temperature of 350°C, in a process known as annealing. This caused the compound to form two distinct phases, with one phase increasingly converted to the other the longer the sample was annealed. Although neither of the two phases was superconducting, Chu and his colleagues were able to detect superconductivity at the point when the two phases coexist.

Although the Tcs of the sample produced through this process was still relatively low, Chu said the method used to prove the concept offers a new direction in the search for more efficient, less expensive superconducting materials.

This story is adapted from material from the University of Houston, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.