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

TL;DR

This paper reports the discovery of anisotropic superconductivity and multiple topological Dirac fermions in Pb$_{1/3}$TaS$_2$, a topological crystalline metal, highlighting its potential for exploring topological superconductivity.

Contribution

It provides the first experimental evidence of superconductivity in Pb$_{1/3}$TaS$_2$ and reveals its topological electronic structure with multiple Dirac fermions and protected surface states.

Findings

Pb$_{1/3}$TaS$_2$ is a quasi-2D superconductor with T_c ≈ 2.8 K.

The material exhibits high anisotropy in its upper critical field (γ_{H_{c2}} ≈ 17).

First-principles calculations show multiple Dirac nodal lines and Dirac points protected by crystalline symmetries.

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 ($\gamma_{H_{c2}}$ = $H_{c2}^{ab}/H_{c2}^{c}$ $\approx$ 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 $k_z = \pi$ 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.