Exotic Superconducting Properties in Topological Nodal Semimetal PbTaSe$_2$

TL;DR

This paper investigates the superconducting properties of the topological nodal-line semimetal PbTaSe$_2$, revealing unique anisotropic critical fields and a full superconducting gap, which suggest potential for topological superconductivity.

Contribution

It provides the first detailed experimental characterization of superconductivity in PbTaSe$_2$, confirming its nodal-line band structure and revealing exotic superconducting behaviors.

Findings

Large anisotropy in upper critical field ($H_{c2}$)

Upward features in $H_{c2}$ in-plane at low temperatures

Full superconducting gap without nodes

Abstract

We report the electronic properties of superconductivity in the topological nodal-line semimetal PbTaSe$_2$. Angle-resolved photoemission measurements accompanied by band calculations confirmed the nodal-line band structure in the normal state of single crystalline PbTaSe$_2$. Resistivity, magnetic-susceptibility and specific heat measurements have also been performed on high-quality single crystals. We observed upward features and large anisotropy in upper critical field ($H_{c2}$) measured in-plane (H//\textbf{ab}) and out-plane (H//\textbf{c}), respectively. Especially, $H_{c2}$ measured in H//\textbf{ab} shows sudden upward features rather than a signal of saturation in ultralow temperatures. The specific heat measurements under magnetic field reveal a full superconducting gap with no gapless nodes. These behaviors in this clean noncentrosymmetric superconductor is possibly related to the underlying exotic physics, providing important clue for realization of topological superconductivity.