Observation of superconductivity in a nontrivial ${\mathcal{Z}}_2$ approximant quasicrystal

Abstract

Superconductivity and nontrivial topology are highly sought-after phenomena in quantum materials. While many topological crystalline materials have been found to exhibit superconductivity, their presence in quasicrystals - materials with a unique aperiodic yet ordered structure - has remained largely unexplored. In this work, we report the discovery of superconductivity in a monoclinic approximant to the decagonal quasicrystal Al${}_{13}$Os${}_4$, that exhibits a high superconducting transition temperature and a nontrivial electronic structure. The resistivity, magnetization, specific heat, and $\hat{I}¼$SR measurements confirm superconductivity with a critical temperature of $\sim 5.47$ K. Detailed electronic structure and symmetry analysis reveal nontrivial state with ${\mathcal{Z}}_2=1$ and spin-polarized conducting surface states. Importantly, we identify three-dimensional saddle point van Hove singularities with substantial flat energy dispersion at the Fermi level, which can enhance superconductivity. Our results highlight a rich interplay between superconductivity and nontrivial electronic states in Al${}_{13}$Os${}_4$, demonstrating it as a unique platform for exploring unconventional superconducting states in quasicrystalline materials.

17 pages, 3 figures