Nodeless superconductivity in β−PdBi2

Abstract

The superconducting gap symmetry of $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{PdBi}}_{2}$ is studied by measuring the London penetration depth $\mathrm{\ensuremath{\Delta}}\ensuremath{\lambda}(T)$ as well as the heat capacity ${C}_{P}(T,B)$. In the low temperature limit, both the penetration depth $\mathrm{\ensuremath{\Delta}}\ensuremath{\lambda}(T)$ and the electronic specific heat ${C}_{e}(T)/T$ follow exponential-type temperature dependence, providing evidence for fully gapped superconductivity in this compound. Analysis of the superfluid density ${\ensuremath{\rho}}_{s}(T)$ suggests single-gap $s$-wave superconductivity for $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{PdBi}}_{2}$, which is further supported by the linear field dependence of the Sommerfeld coefficient ${\ensuremath{\gamma}}_{0}(B)$ determined in the superconducting state.