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.
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 superconduct 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. One approach to solving this problem has been to study compounds that have similar crystal, magnetic and electronic structures to the cuprates.
Nickel-based oxides - nickelates - have long been considered as potential cuprate analogs because the element sits immediately adjacent to copper in the periodic table
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. But the lanthanum analog is non-metallic and adopts a so-called "charge-stripe" phase, an electronic property that makes the material an insulator, the opposite of a superconductor.