Probing the superconducting gap symmetry of $\hat{I}\pm$-PdBi${}_2$: A penetration depth study

Abstract

We report measurements of the in-plane London penetration depth $\hat{I}»$ in single crystals of the $\hat{I}\pm$-PdBi${}_2$ superconductor --- the $\hat{I}\pm$-phase counterpart of the putative topological superconductor ${\hat{I}}^2$-PdBi${}_2$, down to 0.35~K using a high-resolution tunnel-diode-based technique. Both $\hat{I}»$ and superfluid density $\ddot{I}{}_s$ exhibit an exponential behavior for $T\le$ 0.35$T_c$, with $\hat{I}”(0)/k_B{T}_c\sim$2.0, $\hat{I}”C/{\hat{I}}^3{T}_c$$\sim$2.0 and $\hat{I}»(0)$$\sim$140~nm, showing that $\hat{I}\pm$-PdBi${}_2$ is a moderately-coupling, fully-gapped superconductor. The values of $\hat{I}”(0)$ and $\hat{I}”C/{\hat{I}}^3{T}_c$ are consistent with each other via strong-coupling corrections.

6 pages, 5 figures