New progress in superconducting hydrides under high pressure
Abstract
<p indent="0mm">In 2004, Ashcroft assumed that hydrides could be metalized and become superconductors under high pressure because of the pre-compression of hydrogen in the compounds. Due to the crystal structure prediction algorithms, numerous hydride structures, including various superconductors at high pressure, are predicted and analyzed. Moreover, some predicted hydrides are synthesized, and their superconductivities are confirmed via experiments. For example, the critical temperature of H<sub>3</sub>S is 203 K at <sc>155 GPa,</sc> while that of LaH<sub>10</sub> is 274 K at <sc>210 GPa.</sc> Notably, both the critical temperatures are close to the ambient temperature. Hence, the study of superconducting hydrides has recently gained huge attention. Most binary hydrides in the sample space are studied through computational methods. Their superconducting properties must be maintained at high pressure. Thus, discovering the superconducting hydrides at lower pressure is an essential task. The study of superconductivity of compressed ternary hydrides has attracted massive interest because of the large sample space. However, the increasing computational costs and numerous ternary hydride candidates pose a major challenge in the study. Additionally, a light hydrogen atom significantly affects the nuclear quantum and anharmonicity in superconductivity. In this article, we introduce the recently discovered superconducting binary hydrides in the latest theoretical and experimental studies. In addition, we review the basic idea of stochastic self-consistent harmonic approximation and its application in analyzing the superconductivity of H<sub>3</sub>S and LaH<sub>10</sub>. The recent progress in the superconducting compressed ternary hydrides is also included, especially those at a low-pressure range. Nowadays, data-driven machine learning methods are applied in various fields. We highlight some successful approaches to predict superconducting hydrides in the lower-pressure range.</p>
