CaPtAs: a new noncentrosymmetric superconductor

Abstract

We report the discovery of a new noncentrosymmetric superconductor CaPtAs. It crystallizes in a tetragonal structure (space group $I{4}_{1}md$, No.109), featuring three dimensional honeycomb networks of Pt-As and a much elongated $c$-axis ($a=b=4.18$ Ã , and $c=43.70$ Ã ). The superconductivity of CaPtAs with $T_c$ = 1.47 K was characterized by means of electrical resistivity, specific heat, and ac magnetic susceptibility. The electronic specific heat $C_{\mathrm{e}}(T)/T$ shows evidence for a deviation from the behavior of a conventional BCS superconductor, and can be reasonably fitted by a $p$-wave model. The upper critical field $\hat{I}{¼}_0{H}_{c2}$ of CaPtAs exhibits a relatively large anisotropy, with an in-plane value of around 204 mT and an out-of-plane value of 148 mT. Density functional theory calculations indicate that the Pt-5$d$ and As-4$p$ orbitals mainly contribute to the density of states near the Fermi level, showing that the Pt-As honeycomb networks may significantly influence the superconducting properties.

9 pages, 8 figures. Accepted for publication in Science China Physics, Mechanics & Astronomy