Paper published in Physical Review B

We are excited to announce that our paper First-principles evidence for conventional superconductivity in a quasicrystal approximant has been published in Physical Review B.

Quasicrystals host long-range order without translational symmetry—a regime in which the very foundations of BCS theory are not straightforwardly applicable. Yet experiments on quasicrystals and their approximant crystals consistently point to conventional, s-wave, electron-phonon coupled superconductivity. In this now peer-reviewed work we resolve that tension from first principles: using state-of-the-art ab initio methods, we compute the superconducting properties of the recently discovered decagonal approximant Al₁₃Os₄ and quantitatively reproduce its bulk T_c. This provides an ab initio determination of T_c for an approximant crystal and establishes that the electron-phonon framework remains predictive in these exotic structural regimes.

Building on that validation, we use the generalized quasichemical approximation for alloy modeling in the decagonal Al-Os family to predict tunable superconductivity in Al₁₃Os_4-xRe_x and Al₁₃Os_4-xIr_x. Iridium substitution suppresses the density of states at the Fermi level and drives Al₁₃Ir₄ dynamically unstable, so only a narrow Os-rich composition range is feasible. Rhenium substitution does the opposite: it raises the density of states, Al₁₃Re₄ is dynamically stable, and we estimate a T_c about 30% above that of Al₁₃Os₄. In Al₁₃Re₄ the Fermi surface gains an enlarged Al-p derived sheet alongside hybridized ones, which suggests a composition-driven crossover from single-gap to multigap superconductivity across the solid solution.

Perhaps most importantly, we discuss the role of approximant crystals as high-fidelity proxies for their parent quasicrystals. Although long-range quasiperiodicity may introduce subtle electronic features, our findings indicate that the key ingredients for superconductivity are already encoded in the local structural motifs that the approximant preserves. This places the Al-Os and Al-Re families among the most promising candidates for the highest-T_c quasicrystalline superconductivity found so far, and opens a concrete route into the search for superconductors in aperiodic systems.

Read the full paper at doi.org/10.1103/qx58-z229.