Predicted High-Temperature Superconducting State in the Hydrogen-Dense Transition-Metal HydrideYH3at 40 K and 17.7 GPa

Metallization in pure hydrogen has been proposed to give rise to high-temperature superconductivity at pressures which still lie beyond the reach of contemporary experimental techniques. Hydrogen-dense materials offer an opportunity to study related phenomena at experimentally achievable pressures. Here we report the prediction of high-temperature superconductivity in yttrium hydride (${\mathrm{YH}}_{3}$), with a ${T}_{c}$ of 40 K at 17.7 GPa, the lowest reported pressure for hydrogen-dense materials to date. Specifically, we find that the face-centered cubic structure of ${\mathrm{YH}}_{3}$ exhibits superconductivity of different origins in two pressure regions. The evolution of ${T}_{c}$ with pressure follows the corresponding change of $s\mathrm{\text{\ensuremath{-}}}d$ hybridization between H and Y, due to an enhancement of the electron-phonon coupling by a matching of the energy level from Y-H vibrations with the peak of the $s$ electrons from the octahedrally coordinated hydrogen atoms.