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 TaS2. Systematic measurements indicate that Pb 1/3 TaS2 is a quasi-two-dimensional (q-2D) type-II superconductor (Tc ≈ 2.8 K) with a significantly enhanced anisotropy of upper critical field (γH c2 = H ab c2 /H c c2 ≈ 17). In addition, first-principles calculations reveal that Pb 1/3 TaS2 hosts multiple topological Dirac fermions in the electronic band structure. We discover four groups of Dirac nodal lines on the kz = π 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 TaS2 is a promising arena to study the interplay between superconductivity and topological Dirac fermions.