Clathrate metal superhydrides at high-pressure conditions: enroute to room-temperature superconductivity

Abstract Room-temperature superconductivity has been a long-held dream of mankind and a focus of considerable interests in the research field of superconductivity. Significant progress has recently been achieved in hydrogen-based superconductors found in superhydrides (hydrides with unexpectedly high hydrogen content) that are stabilized at high pressure conditions and are not capturable at ambient conditions. Of particular interest is on the discovery of a class of best-ever-known superconductors in clathrate metal superhydrides that hold the record high superconductivity (e.g., Tc = 250–260 K for LaH10) among known superconductors and have a great promise to be the ones that realize the long-sought room-temperature superconductivity. In this peculiar clathrate superhydrides, hydrogen forms unusual “clathrate” cages containing encaged metal atoms, of which such a kind was first reported in a calcium hexa-superhydride (CaH6) showing a measured high Tc of 215 K under a pressure of 170 GPa. In this review, we aim to offer an overview on the current status of research progress on the clathrate metal superhydrides superconductor, discuss the superconducting mechanism, and highlight the key features (e.g., structure motifs, bonding features, and electronic structure, etc.) that govern the high-temperature superconductivity. Future research direction along this line to find room temperature superconductors will be discussed.