The coexistence of two opposing phenomena might be the secret to understanding the enduring mystery in physics of how materials heralded as the future of powering our homes and communities actually work.
Story content courtesy of Princeton University and Brookhaven National Laboratory, US
This insight could help spur the further development of high-efficiency electric-power delivery. The recently-published findings provide a substantial clue for unraveling the inner workings of high-temperature superconductors (HTS) based on compounds containing copper and oxygen, or copper oxides.
The secret to high-temperature superconductivity may lie at the junction of that state and its near opposite, notes Ali Yazdani, a Princeton physics professor and the paper’s senior author. The researchers report that high-temperature superconductivity in copper oxides forms as the material is cooled from a state in which electrons exhibit what is normally considered a competing behavior called “charge ordering.” In a superconductor, electrons overcome their repulsion and form pairs that move in unison and conduct electricity without resistance. In a charge-ordered state, interaction between electrons keeps them locked into a rigid pattern, which usually limits their ability to make the freely moving pairs required for superconductivity.
“Charge ordering is when every electron knows its place and stays there - in a superconductor, they know their place but they move in unison,” Yazdani said. “It’s almost like they freeze into this patterned charge-order state, and just before they become stuck they change their minds and do exactly the opposite.”
The researchers’ finding provides an important indication about the point at which a material potentially becomes an HTS, Yazdani said. From there, scientists may one day figure out how to enhance superconductivity, possibly even determining how it can occur at higher temperatures, he said.
The work was supported by the U.S. Department of Energy Basic Energy Sciences, the National Science Foundation (grant DMR1104612), the Eric and Wendy Schmidt Transformative Technology Fund, and the W.M. Keck Foundation.