Phonon softening and strong-coupling superconductivity in metastable Sb0.83Au0.17

Abstract

A central question in superconductivity is how a semimetal such as antimony, normally nonsuperconducting, can host a robust superconducting state upon Au incorporation. We investigate this problem in metastable Sb0.83Au0.17, which crystallizes in the simple cubic α−Po-type structure stabilized through high-pressure and high-temperature synthesis. Bulk measurements of magnetic susceptibility, resistivity, and heat capacity establish type-II superconductivity with Tc≈8K. The superconducting state exhibits strong electron-phonon coupling (λep=0.91) and the single-gap s-wave model yields a superconducting gap of Δ= 2.02 kBTc, exceeding the BCS weak-coupling limit. Heat-capacity data reveal low-energy Einstein modes and a pronounced Boson peak in the CphononT3 vs T plot, highlighting phonon softening as a key factor in the enhanced coupling. We argue that the emergence of superconductivity is driven by the cooperative effect of soft phonons and strong electron-phonon interactions. Density-functional theory calculations indicate a finite density of states at the Fermi level, consistent with a metallic behavior in contrast to the semimetallic nature of pristine Sb.

Source-reported materials — not catalogue approval

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