An international team led by Artem R. Oganov, at Skolkovo Institute of Science and Technology (Skoltech), and Dr.Ican Troyan from the Institute of Crystallography of RAS, recently investigated a new high-temperature superconductor, yttrium hydride (YH6) in a bid to attain room-temperature superconductivity at lower pressures.
Their research, published in the journal Advanced Materials, details their experiments on yttrium hydride, which was first theorized by Chinese scientists in 2015, a Skoltech press release explains.
"Until 2015, 138 K (or 166 K under pressure) was the record of high-temperature superconductivity. Room-temperature superconductivity, which would have been laughable just five years ago, has become a reality. Right now, the whole point is to attain room-temperature superconductivity at lower pressures," says Dmitry Semenok, a co-author of the paper and a Ph.D. student at Skoltech.
Yttrium hydrides rank amongst the three highest-temperature superconductors known to the scientific community. The top-ranking superconductor is a material with an unknown S-C-H composition and superconductivity at 288 K. This is followed by lanthanum hydride, LaH10, which superconducts at temperatures up to 259 K. Finally, yttrium hydrides, YH6 and YH9, have superconductivity temperatures of 224 K and 243 K, respectively.
Discrepancies between superconductivity theory and experiments
The highest temperature superconductors were first predicted in theory and before being created and investigated in experiments. That was also the case with yttrium hydride.
"First, we look at the bigger picture and study a multitude of different materials on the computer. This makes things much faster. The initial screening is followed by more detailed calculations. Sorting through fifty or a hundred materials takes about a year, while an experiment with a single material of particular interest may last a year or two," Oganov comments.
Critical superconductivity temperatures are typically predicted by theory with an error margin of about 10-15% — this is a similar accuracy to that achieved by critical magnetic field predictions.
With yttrium hydride, the theory was further off the mark than usual. The critical magnetic field observed in experiments is 2 to 2.5 times larger than was predicted in theory. This is the first time scientists have encountered such a large discrepancy, something that, so far, remains a mystery.
As the Skoltech press release points out, there might be some unaccounted for physical effects that contribute to the superconductivity of the material.
In October 2020, researchers from the University of Rochester became the first to achieve room-temperature superconductivity. TIME Magazine later wrote: "Let’s be clear: hoverboards, magnetic levitation trains and resistance-free power lines are not coming this year or next. But thanks to Ranga Dias [University of Rochester lead researcher], they’re closer than they ever were."
Superconducting materials promise a whole host of technological applications and advances related to quantum computing, levitating trains, and even lunar archiving.