Anisotropic superconductivity in topological crystalline metal Pb${}_{1/3}$TaS${}_2$ with multiple Dirac fermions

Abstract

Topological crystalline metals/semimetals (TCMs) have stimulated a great research interest, which broaden the classification of topological phases and provide a valuable platform to explore topological superconductivity. Here, we report the discovery of superconductivity and topological features in Pb-intercalated transition-metal dichalcogenide Pb${}_{1/3}$TaS${}_2$. Systematic measurements indicate that Pb${}_{1/3}$TaS${}_2$ is a quasi-two-dimensional (q-2D) type-II superconductor ({\em T}${}_c\approx$ 2.8 K) with a significantly enhanced anisotropy of upper critical field (${\hat{I}}_{H_{c2}}^3$ = $H_{c2}^{ab}/H_{c2}^c$ $\approx$ 17). In addition, first-principles calculations reveal that Pb${}_{1/3}$TaS${}_2$ hosts multiple topological Dirac fermions in the electronic band structure. We discover four groups of Dirac nodal lines on the $k_z=\ddot{I}€$ plane and two sets of Dirac points on the rotation/screw axes, which are protected by crystalline symmetries and robust against spin-orbit coupling (SOC). Dirac-cone-like surface states emerge on the (001) surface because of band inversion. Our work shows that the TCM candidate Pb${}_{1/3}$TaS${}_2$ is a promising arena to study the interplay between superconductivity and topological Dirac fermions.