Superfluid Density and Flux-Flow Resistivity Measurements of Multiple-Band Superconductor $\beta$-PdBi$_{2}$

$\beta$-PdBi$_2$ ($T_{\rm c}^{\rm max}=5.4$ K) is a newcomer of the multiple-band superconductors, revealed by the specific heat and the upper critical field measurements [1], and the angle-resolved photoemission spectroscopy [2]. In addition, authors of ref. [2] observed the spin-polarized band dispersion and proposed that $\beta$-PdBi$_2$ is a candidate of topological superconductor. However, there is less information on superconducting properties so far. In order to clarify the superconducting gap function, we measured the temperature ($T$) and magnetic field ($B$) dependence of microwave complex conductivity of $\beta$-PdBi$_2$ single crystals. We found that the superfluid density exhibits the thermally activated $T$ dependence, manifesting the absence of nodes in the superconducting gaps. We also found that the flux-flow resistivity increased with $B$ with downward-convex shape. Based on some theories, we considered that such a behavior originated from the backflow of supercurrents around vortices reflecting rather small Ginzburg-Landau parameter ($\kappa\simeq5$). [1] Y. Imai {\it et al}., JPSJ {\bf 81}, 113708 (2011). [2] M. Sakano {\it et al}., arXiv:1505.07231.