Absence of superconductivity in fcc metallic hydrogen and low in yttrium hydrides resulting from distinct vibrational modes of hydrogen sublattices
Phys. Rev. B 114, 094102 – Published 5 August, 2026
DOI: https://doi.org/10.1103/3k9s-p873
Abstract
Hydrides and solid hydrogen have long been considered potential high-temperature, and even room-temperature, superconductors, owing to the exceptionally high Debye temperature provided by their hydrogen atoms. However, we observed unexpected suppression of superconductivity in yttrium hydrides and metallic hydrogen systems. Our study demonstrates that the vibrational characteristics of the hydrogen sublattice constitute a critical factor influencing superconducting transition temperatures. We find that in H-poor yttrium hydrides, the anomalously low superconducting transition temperature originates from hydrogen-dominated acoustic-like vibrations. Strikingly, even in fcc metallic hydrogen—which exhibits the highest Debye temperature among known systems—the acoustic-like vibrational behavior of hydrogen results in an extremely weak polarization field and negligible electron-phonon coupling, severely limiting superconductivity. While alkali metals have long been regarded as the closest realization of an ideal free-electron metal, we demonstrate that fcc metallic hydrogen actually represents the closest embodiment of this fundamental model. Furthermore, our study reveals that the zero-resistance state in fcc metallic hydrogen originates from negligible electron-lattice scattering, rather than the suppression of transport electron scattering by superconducting gap pairs as predicted by BCS theory. Consequently, the transition to zero resistance in fcc metallic hydrogen occurs without passing through a thermodynamic phase transition of electron Cooper pair condensation, but rather manifests as a natural consequence of its perfect metallic properties.
