Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu₃ with a Critical Temperature of 42 K under Atmospheric Pressure

Abstract Since the prediction of multi‐hydrogen high‐temperature superconductor by Ashcroft in 2004, many possible candidates have been proposed, e.g., LaH₁₀ showing the highest superconducting transition temperature (T_c) around 250–260 K at 170‐200 GPa hitherto. However, this pressure is too large to be taken into practical use. To address this challenge, it proposes a few‐hydrogen metal‐bonded perovskite superconductor, MgHCu₃, by combining a novel design idea with first‐principles calculations. Different from multi‐hydrogen hydrides, whose high T_c relies on extreme pressure, the metallic bond in few‐hydrogen superconductor MgHCu₃ improves the structural stability and ductility at atmospheric pressure. Here, the small amount of hydrogen is found to be vital for T_c. After the incorporation of hydrogen, the electron–phonon coupling constant of MgHCu₃ is increased to 0.83, which is larger than that of the well‐known MgB₂. Moreover, the anisotropy of MgHCu₃ also plays an important role in enhancing T_c. Based on the Migdal‐Eliashberg theory, it predicts that the phonon‐mediated metal‐bonded perovskite MgHCu₃ is a superconductor with T_c of 42 K. The first predicted ternary metal‐bonded perovskite, MgHCu₃, enriches the family of perovskite and will promote further investigation on few‐hydrogen superconductors under atmospheric pressure.