Metastability and high-Tc superconductivity in A15-type ternary hydride YSbH6 at moderate pressure

Abstract

The discovery of high-temperature superconductors remains a central challenge in materials science. Hydrogen-rich compounds are among the most promising candidates, as they can exhibit phonon-mediated superconductivity at elevated critical temperatures, though their stabilization typically requires extreme pressures. Here, we report the identification of YSbH6 as a promising superconductor by a multistage high-throughput screening on ternary A15-type hydrides, followed by a high-throughput computational search of the Y-Sb-H system, accelerated by ephemeral data derived potentials. The cubic Pm3¯ YSbH6 phase exhibits a predicted critical temperature of 118 K at 50 GPa, among the highest Tc reported to date for an A15 hydride at this pressure. Thermodynamic analysis shows that YSbH6 lies ∼100meV/ atom above the convex hull at 50 GPa, but only 26 meV/atom above the hull at 120 GPa, suggesting possible metastability and synthesis at similar high-pressure conditions. The phase is dynamically stable over a wide pressure range (20–120 GPa), displays kinetic stability at 50 GPa, and elastic stability at 20 and 50 GPa, key ingredients for long-lived metastable behavior at moderate pressures. These results highlight YSbH6 as a benchmark case illustrating the balance between high-Tc performance and limited thermodynamic stability in ternary hydrides, and underscore the importance of combined dynamic, thermodynamic, kinetic, and elastic stability analyses for guiding experimental synthesis of metastable superconductors.

Source-reported materials — not catalogue approval

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