Ductile Copper-Based Hydride Superconductors at Tc ∼ 60 K with a New Paradigm under Ambient Pressure

Abstract Although multi-hydrogen superconductors have shown transition temperature ( T c ) above 200 K, the required ultra-high pressure, as well as poor ductility, hinders their practical use. Several synthesized ambient-pressure ones face critical challenges, such as low T c values and a lack of a clear underlying mechanism. Here, in view of the synthesis of several copper hydrides, which is based on one of the most important non-superconducting metals with excellent ductility and abundance, we investigate the mechanical and superconducting properties of the Cu-H system by first-principles calculations and Migdal-Eliashberg theory. Two effective approaches to enhancing T c are found: increasing the interstitial space and ratio of hydrogen. Expanding the interstitial space for H to around 13.92% in cubic-Cu 4 H model shows potential for realizing high T c ∼ 56 K. In particular, by increasing hydrogen ratio properly, we found a new intrinsic tetra-Cu 2 H phase with T c ∼ 60 K and excellent ductility under atmospheric pressure. The comprehensive analysis leads to a paradigm for enhancing T c of ambient-pressure metal hydrides: highly symmetric structure with soft H phonons and dominant s/p orbital at Fermi level can induce high T c . Last but not least, we examine the structural stability of the Cu-H system from multiple aspects, and propose feasible synthesis routes that have been demonstrated to be highly accessible through our ab initio molecular dynamics simulations. The discovery of ductile Cu-based hydride superconductors, tetra-Cu 2 H, along with the paradigm for realizing ambient-pressure high- T c superconductivity in metal hydrides, paves the way for exploring more practical superconductors.