Structures and Superconductivity of Hydrogen and Hydrides under Extreme Pressure

TL;DR

This review discusses recent advances in the study of hydrogen and hydrides under extreme pressure, emphasizing their structures, phase diagrams, and the pursuit of high-temperature superconductivity, including near-ambient pressure conditions.

Contribution

It provides a comprehensive overview of theoretical and experimental progress in high-pressure hydrogen and hydrides, highlighting structural features relevant to superconductivity.

Findings

Hydrides exhibit record high superconducting transition temperatures.

Simulations have successfully predicted structures and superconducting properties.

Progress toward hydrogen-driven superconductivity near ambient pressure.

Abstract

Metallic hydrogen, existing in remarkably extreme environments, was predicted to exhibit long-sought room-temperature superconductivity. Although the superconductivity of metallic hydrogen has not been confirmed experimentally, superconductivity of hydrogen in hydrides was recently discovered with remarkably high critical temperature as theoretically predicted. In recent years, theoretical simulations have become a new paradigm for material science, especially exploration of material at extreme pressure. As the typical high-pressure material, metallic hydrogen has been providing a fertile playground for advanced simulations for long time. Simulations not only provide the substitute of experiments for hydrogen at high-pressure, but also encouraged the discovery of almost all the experimentally discovered superconducting hydrides with the record high superconducting transition temperature. This work reviews recent progress in hydrogen and hydrides under extreme pressure, focusing on phase diagram, structures and the long-sought goal of high-temperature superconductivity. In the end, we highlight structural features of hydrides for realization of hydrogen-driven superconducting hydrides near ambient pressure.