# Probing the superconducting gap symmetry of $\alpha$-PdBi$_{2}$: A penetration depth study

## TL;DR

This study investigates the superconducting gap symmetry of $ ext{α}$-PdBi$_{2}$ by measuring the London penetration depth, revealing it to be a fully-gapped, moderately-coupling superconductor with strong-coupling characteristics.

## Contribution

The paper provides the first detailed penetration depth measurements of $ ext{α}$-PdBi$_{2}$, demonstrating its fully-gapped, strong-coupling superconducting nature.

## Key findings

- Exponential behavior of $ ext{λ}$ and $
ho_s$ at low temperatures.
- Superconducting gap ratio $ ext{Δ(0)}/k_B T_c ext{≈ 2.0}$.
- Superfluid density indicates a fully-gapped superconductor.

## Abstract

We report measurements of the in-plane London penetration depth $\lambda$ in single crystals of the $\alpha$-PdBi$_{2}$ superconductor --- the $\alpha$-phase counterpart of the putative topological superconductor $\beta$-PdBi$_{2}$, down to 0.35~K using a high-resolution tunnel-diode-based technique. Both $\lambda$ and superfluid density $\rho_{s}$ exhibit an exponential behavior for $T\leq$ 0.35$T_{c}$, with $\Delta(0)/k_{B}T_{c}\sim$2.0, $\Delta C/\gamma T_{c}$$\sim$2.0 and $\lambda(0)$$\sim$140~nm, showing that $\alpha$-PdBi$_{2}$ is a moderately-coupling, fully-gapped superconductor. The values of $\Delta(0)$ and $\Delta C/\gamma T_{c}$ are consistent with each other via strong-coupling corrections.