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

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, $T_{\mathrm{c}}$, is found to be robust against disorders, which suggests that the pairing should be sign-preserved rather than sign-reversed.

9 pages, 7 figures