High-pressure synthesis of superconducting clathratelike YH4

Pursuing room-temperature superconductors has been a major theme in physics and material sciences since the discovery of superconductivity in 1911. In light of the tremendous progress that has been made in hydrogen-based superconductors with record T-c similar to 260 K in binary fcc LaH10, it is natural to explore more similar phases in hydrogen-rich materials. Y and La are conventionally grouped together with the lanthanide elements due to the similarities in their outer electron configurations and properties. The yttrium-hydrogen system is the most attractive candidate with high T-c among all binary metal-hydrogen systems theoretically studied so far. Here we report the synthesis of the I4/mmm-YH4 phase and determine its superconducting transition with maximum T-c similar to 88 K at 155 GPa. The decrease in critical temperature under an external magnetic field suggests the upper critical magnetic field of about 14-22 T at megabar pressures consistent with theoretical data. By making the overlapping analysis, we elucidate that the stabilization of clathrate structures through Y atoms and the high-frequency hydrogen sublattice vibrations contribute effectively to strong electron-phonon coupling and therefore high-temperature superconductivity in the I4/mmm-YH4 and Im (3) over barm-YH6 phases.

Automated summary

This research reports the synthesis of the I4/mmm-YH4 phase and determines its maximum superconducting transition temperature at 88K under high pressure. The study shows that the stable clathrate structure and high-frequency hydrogen sublattice vibrations contribute effectively to high-temperature superconductivity.