Minghu Pan's image of "clover-like" atomic defects—an example is circled—that result in strong superconductivity. Image: Oak Ridge National LaboratoryNearly 30 years after the discovery of high-temperature superconductivity, many questions remain, but an Oak Ridge National Laboratory (ORNL) team is providing insight that could lead to better superconductors.

Their work, published in Physical Review Letters, examines the role of chemical dopants, which are essential to creating high-temperature superconductors. The role of dopants in superconductors is particularly mysterious as they introduce non-uniformity and disorder into the crystal structure, which increases resistivity in non-superconducting materials.

By gaining a better understanding of how and why chemical dopants alter the behavior of the original (parent) material, scientists believe they can design superconductors that work at higher temperatures. This would make them more practical for real-world wire applications because it would lessen the extreme cooling required for conventional superconducting material. Existing high-temperature superconductors operate at temperatures in the range of negative 135 C and below.

“Through this work, we have created a framework that allows us to understand the interplay of superconductivity and inhomogeneity,” said lead author Krzysztof Gofryk, a postdoctoral fellow in the U.S. Dept. of Energy laboratory’s Materials Science and Technology Div. “Thus, for the first time we have a clearer picture of the side effects of dopants.”


“Our bulk and atomic-scale measurements on an iron-based superconductor have revealed that strong superconductivity comes from highly doped regions in the crystal where dopants are clustered,” Sefat said. “If we can design a crystal where such clusters join in an organized manner, we can potentially produce a much higher performance superconductor.”


Source: Oak Ridge National Laboratory