Superconductivity of the hydrogen-rich metal hydride L i5Mo H11 under high pressure

Ternary metal hydrides are convenient and valuable systems for investigating the metallization and superconductivity of metal hydrides because they can be synthesized under mild conditions and recovered under ambient pressure. In this study, the conducting behavior and structural phase transition of a hydrogen-rich metal hydride, Li5MoH11, were investigated at pressures up to 210 GPa in a diamond anvil cell. The results showed that Li5MoH11 transforms from an insulator to a poor metal at around 100 GPa. Superconductivity was observed at 100 GPa and retained until 210 GPa, and its maximum onset transition temperature was 6.5 K at 160 GPa. High-pressure synchrotron x-ray diffraction experiments revealed that the ambient-pressure hexagonal crystal structure is retained until at least 130 GPa. Furthermore, apart from the influence of pressure on the conducting behavior of Li5MoH11, the effect of annealing time on the conducting and superconducting behaviors at room temperature and high pressure were also observed. We hypothesized that this time-dependent behavior is due to the restoration of the MoH9 cage structure after distortion or rotation caused by pressurization. These findings provide insight on the conducting and superconducting behaviors of ternary metal hydrides that, until recently, have been mostly studied by theoretical methods.