Nickel for thought: Compound shows potential for high-temperature superconductivity
A team of researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory has identified a nickel oxide compound as an unconventional but promising candidate material for high-temperature superconductivity. The team successfully synthesized single crystals of a metallic trilayer nickelate compound, a feat the researchers believe to be a first. This nickel oxide compound does not super conduct, said John Mitchell, an Argonne Distinguished Fellow and associate director of the laboratory’s Materials Science Division, who led the project, which combined crystal growth, X-ray spectroscopy, and computational theory.
Mitchell and seven co-authors announced their results in this week’s issue of Nature Physics. Superconducting materials are technologically important because electricity flows through them without resistance. High-temperature superconductors could lead to faster, more efficient electronic devices, grids that can transmit power without energy loss and ultra-fast levitating trains that ride frictionless magnets instead of rails. Only low-temperature superconductivity seemed possible before 1986, but materials that super conduct at low temperatures are impractical because they must first be cooled to hundreds of degrees below zero. In 1986, however, discovery of high-temperature superconductivity in copper oxide compounds called cuprates engendered new technological potential for the phenomenon. But after three decades of ensuing research, exactly how cuprate superconductivity works remains a defining problem in the field.
The nickelate that the Argonne team has created is a quasi-two-dimensional trilayer compound, meaning that it consists of three layers of nickel oxide that are separated by spacer layers of praseodymium oxide. This nickelate and a compound containing lanthanum rather than praseodymium both share the quasi-two-dimensional trilayer structure. Argonne is one of a few laboratories in the world where the compound could be created. The Materials Science Division’s high-pressure optical-image floating zone furnace has special capabilities. It can attain pressures of 150 atmospheres and temperatures of approximately 2,000 degrees Celsius, conditions needed to grow the crystals.