Ductile copper hydride Eliashberg superconductors with <i>T</i>_c in the liquid-nitrogen temperature range and band topology at ambient pressure

The engineering demands for superconductors require not only a high transition temperature (<i>T</i>_c) but also eco-friendliness, mechanical workability, and abundance. Currently, superconductors exhibiting both mechanical ductility and <i>T</i>_c above the liquid-nitrogen temperature are still lacking. Considering that copper is one of the most important conductive materials for power transmission, we investigate the synthetic routes, band topology, electron-phonon coupling (EPC) and anharmonic superconductivity of copper hydrides using first-principles calculations. Cubic-Cu₄H₃ remains stable at ambient pressure after kinetic simulations from its experimentally synthesized pressure state. The incorporation of hydrogen impacts the ductility of Cu₄H₃ negligibly compared to copper, while enabling high-<i>T</i>_c superconductivity up to 77 K and non-trivial band topology at ambient pressure. The novel properties arise from the strong EPC, Fermi surface nesting and hydrogen-induced band inversion. This discovery may fill the gap in the lack of ductile superconductors in the liquid-nitrogen temperature range and pave a new way for realizing high-temperature topological superconductivity at atmospheric pressure.