Superconductivity observed at near room temperatures
doi:10.1038/nindia.2019.10 Published online 30 January 2019
Physicists have synthesised a new class of superhydrides, hydrogen-rich materials that, when cooled at high pressures near room temperature, exhibits superconductivity1. This work could be a significant step towards making the generation, transmission and use of electricity more efficient.
The theory of superconductivity, formulated by John Bardeen, Leon Cooper and Robert Schrieffer, explains that a current of electron pairs flows without any resistance in certain materials at extremely low temperatures.
Previous experiments had displayed such low-temperature superconductivity in specific non-metallic and metallic materials. However, superconductivity at high temperatures, particularly near room temperatures, remained elusive.
Following up recent theoretical predictions that hydrogen-rich materials could exhibit superconductivity, an international research team, including a physicist from the Bhabha Atomic Research Centre in Mumbai, India, prepared lanthanum superhydrides by heating lanthanum and ammonia borane with a laser in a tiny diamond anvil cell.
They then cooled the superhydrides and measured their electrical conductivity using multi-probe electrical contacts. The resistance of the samples started falling at around 70C, and “dropped appreciably” at -130C, at pressures around two million times that of the Earth’s atmosphere.
The researchers say that the resistance drop observed in these samples is a signature of nearly room-temperature superconductivity. They attribute such superconductivity of these superhydrides to a novel clathrate-type structure in which at least 32 hydrogen atoms surround a lanthanum atom, causing a specific transition in electronic structure and stretched hydrogen bonds.
1. Somayazulu, M. et al. Evidence for superconductivity above 260 K in lanthanum superhydride at megabar pressures. Phys. Rev. Lett.122, 027001(2019)