Anomalous Residual Surface Conductivity in a Superconductor with Strong Spin-Orbit Coupling

Abstract

Conventional BCS superconductors are expected to exhibit a conductivity with vanishing dissipation with decreasing temperature. While bulk physical properties measurements indicate PdPb${}_2$ is a conventional superconductor with a $T_c$ of 3.0 K, measurements of surface impedance through the microwave cavity perturbation technique indicate a large, non-vanishing dissipative component below $T_c$ that is at odds with conventional superconductivity. We demonstrate PdPb${}_2$ to be a possible topological superconductor with a fully gapped bulk and a dissipative Majorana fluid surface.