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., LaH 10 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, MgHCu 3 , 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 MgHCu 3 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 MgHCu 3 is increased to 0.83, which is larger than that of the well‐known MgB 2 . Moreover, the anisotropy of MgHCu 3 also plays an important role in enhancing T c . Based on the Migdal‐Eliashberg theory, it predicts that the phonon‐mediated metal‐bonded perovskite MgHCu 3 is a superconductor with T c of 42 K. The first predicted ternary metal‐bonded perovskite, MgHCu 3 , enriches the family of perovskite and will promote further investigation on few‐hydrogen superconductors under atmospheric pressure.