Advances in the Synthesis and Superconductivity of Lanthanide Polyhydrides Under High Pressure

Abstract

Room-temperature superconductors have long been the ultimate goal of scientists. Pressure-stabilized hydrides are a new rapidly growing class of high-temperature superconductors and are believed to be a new superconducting system, undoubtedly leading to a surge in the discovery of new hydrogen-rich materials. They are the forefront of physics and material science. Lanthanide polyhydrides formed under pressure are promising conventional superconductors. Especially, both the theoretical and experimental reports on lanthanum superhydrides under pressure, exhibiting superconductivity at temperatures as high as 250 K, have further stimulated an intense search for room-temperature superconductors in hydrides. This review focuses on the recent advances of crystal structures, stabilities, and superconductivity of lanthanide polyhydrides at high pressures, including the experimental results from our group. By using in situ four-probe electrical measurements and the synchrotron X-ray diffraction technique, we have identified several high-temperature superconducting phases: a lanthanum superhydride and two cerium superhydrides. The present work indicates that superconductivity declines along the La–Ce–Pr–Nd series, while magnetism becomes more and more pronounced. These discoveries have enriched the binary system of clathrate superhydrides and provided more hints for studying the role of rare earth metal elements having high-temperature superconductivity.