Lanthanum hydrides exhibit superconductivity at record high temperatures.
The electrical resistance of superconducting materials is zero, which allows them to conduct current without the usual losses. However, this has been achieved so far only at extremely low temperatures, which is why the use of superconductors is limited to those areas of technology where it is possible to create suitable cryogenic conditions for them: for example, in electromagnets of maglev or particle colliders.
But scientists continue to search for new materials that exhibit these properties at temperatures increasingly closer to normal. The first discovered superconductors required cooling to only a few degrees above absolute zero (-273 ° C), and in 2015 it was shown that hydrogen sulfide at high pressures demonstrates superconductivity “only” at -70 ° C. This record was recently surpassed, and twice at once.
In the first paper, presented in the arXiv.org preprint library, Russell Hemley and colleagues report superconductivity at an impressive temperature of only -13 ° C (260 K). The effect was observed in lanthanum superhydride, under a pressure of 190 GPa - almost two million atmospheres - which was created by squeezing it between a pair of diamond crystals. According to scientists, in some samples, superconductivity was retained even at "plus" temperatures, up to 280 K.
In the same way, high (up to 170 GPa) pressure was created in lanthanum hydrides, which were experimented with by a team of our former compatriots working at the German Institute of Chemistry of the Max Planck Society, in the group of Mikhail Eremets. In an article published on arXiv.org, scientists report that the material's resistance dropped sharply at 215 K (-58 ° C).
Lanthanum and hydrogen were compressed on a diamond anvil.
It can be noted that the substances used by both teams of scientists are similar: perhaps in both cases we are talking about the same compound of lanthanum and hydrogen. However, so far this cannot be said for sure: of the two groups, only Russell Hemley and his colleagues managed to carry out an X-ray study of the hydride structure. Apparently, in this case, it forms crystals with LaH10 molecules, the superconducting properties of which were previously predicted by the authors.
Let us add that these works do not yet claim to be final: in a hurry to report on new impressive records, the authors submitted articles without due consideration by experts, as is done in academic publications. Both Eremets' group and Hemley and his team have yet to conduct truly thorough experiments, formalize and explain their results - and only then will the superconductivity record be officially updated.
Promotional video:
Sergey Vasiliev