Superconductivity induced by aging and annealing in K1−δCr3As3Hx

Abstract

There has been a puzzling discrepancy on the physical property of quasi-one-dimensional Cr-based compound ${\mathrm{KCr}}_{3}{\mathrm{As}}_{3}$. While the polycrystalline ${\mathrm{KCr}}_{3}{\mathrm{As}}_{3}$ was originally reported to be nonsuperconducting with a spin-glass ground state, the single-crystalline ${\mathrm{KCr}}_{3}{\mathrm{As}}_{3}$ was later found to exhibit superconductivity at $\ensuremath{\sim}5$ K. Here we demonstrate that both the polycrystals and single crystals can be made either nonsuperconducting or superconducting. The pristine samples show a spin-glass behavior only, and superconductivity below 5 K is actually induced by the post-aging and/or post-annealing. The result can be understood in terms of hydrogen intercalation into the one-dimensional ${\mathrm{Cr}}_{3}{\mathrm{As}}_{3}$ tubes, which was discovered very recently by K. M. Taddei et al. (arXiv:1905.03360). In addition, significant K deficiency and microscopic inhomogeneity have been revealed, suggesting a phase separation scenario with columnar superconductivity in ${\mathrm{K}}_{1\ensuremath{-}\ensuremath{\delta}}{\mathrm{Cr}}_{3}{\mathrm{As}}_{3}{\mathrm{H}}_{x}$. The possible processes of the hydrogen intercalation are given.