An international group of scientists led by Professor Skoltech and NUST MISIS Artem Oganov and Dr. Ivan Troyan from the Institute of Crystallography of the Russian Academy of Sciences theoretically and experimentally investigated a new high-temperature superconductor – yttrium hydride (YH6). The research results are published in the journal Advanced Materials.
Yttrium hydrides are among the three highest-temperature superconductors currently known. In the first place in this trio is a substance with an unknown composition in the SCH system and superconductivity at a temperature of 288 K, in the second place is lanthanum hydride LaH10 (superconductivity temperature up to 259 K), and in the third place are yttrium hydrides YH6 and YH9 with a maximum superconductivity temperature of 224 Kelvin. (-49.15 ° C) and 243 K (-30.15 ° C), respectively. Superconductivity of YH6 was predicted by Chinese scientists in 2015. All of these hydrides reach their maximum superconducting temperatures at very high pressures: 1.4 to 2.7 million atmospheres. It is the need for high pressure that is the main obstacle to mass production of them in large volumes.
Until 2015, the record high-temperature superconductivity was 138 K (-135.15 ° C), 166 K (-107.15 ° C) under pressure. Now the goal of scientists is to obtain room superconductivity at lower pressures.
The highest-temperature superconductors were first predicted by theory and then created and studied experimentally. First of all, chemists who study new substances make theoretical predictions, and then they test them in practice.
Usually, theoretical calculations make it possible to predict the critical temperatures of superconductivity with an error of about 10-15%, as well as critical magnetic fields with comparable accuracy. In the case of yttrium hydride YH6, theory and experiment are in poor agreement. For example, the experimental critical magnetic field turns out to be 2-2.5 times higher than the theoretical predictions. This is the first time scientists have encountered this, and an explanation has yet to be found. It is possible that this substance contains additional physical effects that were not taken into account in previous theoretical works.