Paper detail

Unconventional pressure dependence of the superfluid density in the nodeless topological superconductor $α$-PdBi$_2$

We investigated the superconducting properties of the topological superconductor $α$--PdBi$_2$ at ambient and external pressures up to 1.77~GPa using muon spin rotation ($μ$SR) experiments. The ambient pressure measurements evince a fully gapped $s$-wave superconducting state in the bulk of the specimen. AC magnetic susceptibility and $μ$SR measurements manifest a continuous suppression of $T_{\rm c}$ with increasing pressure. In parallel, we observed a significant decrease of superfluid density by $\sim$20\% upon application of external pressure. Remarkably, the superfluid density follows linear relation with $T_{\rm c}$ which was found before in some unconventional topological superconductors and hole doped cuprates. This finding signals a possible crossover from BEC to BCS in $α$--PdBi$_2$.