Absence of Andreev bound states inβ−PdBi2probed by point-contact Andreev reflection spectroscopy

Abstract

We report point-contact spectroscopic studies on high quality single crystalline $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{PdBi}}_{2}$ with a superconducting ${T}_{c}=5.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Our measurements show a typical double-peak structure in the voltage-biased junction conductance at low temperatures, probably excluding the existence of topological Andreev bound states. The conductance curves can be well fitted with the standard Blonder-Tinkham-Klapwijk model for $s$-wave superconductors, yielding a superconducting gap ${\mathrm{\ensuremath{\Delta}}}_{0}\ensuremath{\simeq}0.92\phantom{\rule{0.28em}{0ex}}\mathrm{meV}$ with $2{\mathrm{\ensuremath{\Delta}}}_{0}/{k}_{B}{T}_{c}\ensuremath{\sim}4.1$. Our results strongly suggest that $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{PdBi}}_{2}$ is a conventional intermediate-coupling $s$-wave superconductor.