Fully gapped superconductivity without sign reversal in the topological superconductor PbTaSe$_2$

TL;DR

This study reveals that PbTaSe$_2$ is a fully-gapped topological superconductor with isotropic s-wave pairing, maintaining its superconducting properties despite disorder, indicating sign-preserved pairing without sign reversal.

Contribution

The paper provides experimental evidence that PbTaSe$_2$ exhibits fully-gapped, sign-preserved superconductivity with isotropic s-wave gaps, challenging the expectation of sign-reversal in topological superconductors.

Findings

PbTaSe$_2$ has fully-gapped superconductivity with isotropic s-wave gaps.

Superconductivity remains robust against non-magnetic disorder.

The pairing is likely sign-preserved rather than sign-reversed.

Abstract

We investigate the superconducting gap function of topological superconductor PbTaSe$_2$. Temperature, magnetic field, and three-dimensional (3D) field-angle dependences of the specific heat prove that the superconductivity of PbTaSe$_2$ is fully-gapped, with two isotropic $s$-wave gaps. The pair-breaking effect is probed by systematically increasing non-magnetic disorders through H$^+$-irradiations. The superconducting transition temperature, $T_{\rm{c}}$, is found to be robust against disorders, which suggests that the pairing should be sign-preserved rather than sign-reversed.