Unlocking the Origin of High-Temperature Superconductivity in Molecular Hydrides at Moderate Pressures

Abstract

The current pressing challenge in the field of superconducting hydride research is to lower the stable pressure of such materials for practical applications. Molecular hydrides are usually stable under moderate pressure, but the underlying metallization mechanism remains elusive. Here, the important role of chemical interactions in governing the structures and properties of molecular hydrides is demonstrated. A new mechanism is proposed for obtaining high-temperature and even room-temperature superconductivity in molecular hydrides and report that the ternary hydride NaKH₁₂ hosts T_c values up to 245 K at moderate pressure of 60 GPa. Both the excellent stability and superconductivity of NaKH₁₂ originate from the fact that the localized electrons in the interstitial region of the metal lattice occupying the crystal orbitals well matched with the hydrogen lattice and forming chemical templates to assist the assembly of H₂ units. These localized electrons weaken the H─H covalent bonds and improve the charge connectivity between the H₂ units, ensuring the strong coupling between electrons and hydrogen-dominated optical phonons. The theory provides a key perspective for understanding the superconductivity of molecular hydrides with various structural motifs, opening the door to obtaining high-temperature superconductors from molecular hydrides at moderate pressures.