Discovery of record-breaking high-T c superconductivity among 5d transition-metal-oxides up to 17.8 K in ReO3.

As an A-site-vacant perovskite-type oxide, ReO3 undergoes sequential pressure-driven structural phase transitions associated with rotations of ReO6 octahedra. In this work, we report the discovery of a superconducting T c(P) dome for the rhombohedral-I phase of ReO3 in the pressure range 12-39 GPa. The rhombohedral-I phase is featured by the nearly close-packed oxygen layers intercalated with Re cations, which is reminiscent of superhydride superconductors. The observed maximum T c (∼ 17.8 K) sets the record of high T c among 5d transition-metal-oxides. First-principles calculations reveal that the strong hybridizations between Re-5d and O-2p orbitals significantly enhance the density of states at the Fermi level and the close-packed oxygen framework directly enhances the electron-phonon coupling. We attributed the observed record high-T c to the synergistic effect of strong hybridizations and oxygen sublattice contribution. The present work establishes a rare case that the light-element oxygen lattice plays a crucial role in assisting the emergence of high-T c superconductivity and provides more clues for further exploring new superconductors in 5d transition-metal oxides via high-pressure or heterostructure engineering.