A multi-university team of researchers has artificially engineered a unique multilayer material that could lead to breakthroughs in both superconductivity research and in real-world applications.
Led by Chang-Beom Eom, the Harvey D. Spangler Distinguished Professor of materials science and engineering and physics at UW-Madison, the group described its breakthrough March 3, 2013, in the advance online edition of the journal Nature Materials.
Superconductors, which presently operate only under extremely cold conditions, transport energy very efficiently. With the ability to transport large electrical currents and produce high magnetic fields, they power such existing technologies as magnetic resonance imaging and Maglev trains, among others. They hold great potential for emerging applications in electronic devices, transportation, and power transmission, generation and storage.
One challenge in the quest to leverage superconductivity is developing materials that work at room temperature. Currently, even unconventional high-temperature superconductors operate below -369 degrees Fahrenheit.
The researchers’ iron-based “pnictide” material is promising, in part, because its effective operating temperature is higher than that of conventional superconducting materials such as niobium, lead or mercury. Pnictide superconductors include compounds made from any of five elements in the nitrogen family of the periodic table.
The new material is composed of 24 layers that alternate between the pnictide superconductor and a layer of the oxide strontium titanate. Layer after layer, the researchers maintained an atomically sharp interface—the region where materials meet—and arranged in a regularly repeating crystal structure.
Layered superconducting materials are increasingly important in highly sophisticated applications. For example, a superconducting quantum interference device, or SQUID, used to measure subtle magnetic fields in magnetoencephalography scans of the brain, is based on a three-layer material.
The new material also has improved current-carrying capabilities, thanks to defects that “pin,” or immobilize tiny magnetic vortices that can limit current flow through the superconductor.
The researchers can tailor the material to achieve extraordinary superconducting properties—in particular, the ability to transport much more electrical current than non-engineered materials. “There’s a need to engineer superlattices for understanding fundamental superconductivity, for potential use in high-field and electronic devices, and to achieve extraordinary properties in the system,” says Eom. “And, there is indication that interfaces can be a new area of discovery in high-temperature superconductors. This material offers those possibilities.”
Funding from the U.S. Department of Energy Office of Basic Energy Sciences, National Science Foundation, and the Air Force Office of Scientific Research supported the researchers’ work. Eom’s collaborators include Eric Hellstrom’s and David Larbalestier’s group at Florida State University; and Xiaoqing Pan’s group at the University of Michigan.