Local suppression of the superfluid density of PuCoGa$_5$ in the Swiss Cheese model

Abstract

We present superfluid density calculations for the unconventional superconductor PuCoGa$_5$ by solving the real-space Bogoliubov-de Gennes equations on a square lattice within the Swiss Cheese model in the presence of strong on-site disorder. We find that despite strong electronic inhomogeneity, one can establish a one-to-one correspondence between the local maps of the density of states, superconducting order parameter, and superfluid density. In this model, strong on-site impurity scattering punches localized holes into the fabric of d-wave superconductivity similar to a Swiss cheese. Already a two-dimensional impurity concentration of $n_{\rm imp} = 4%$ gives rise to a pronounced short-range suppression of the order parameter and a suppression of the superconducting transition temperature $T_c$ by roughly 20% compared to its pure limit value $T_{c0}$, whereas the superfluid density $\rho_s$ is reduced drastically by about 70%. This result is consistent with available experimental data for aged (400 day-old) and fresh (25 day-old) PuCoGa$_5$ superconducting samples. In addition, we show that the $T^2-$dependence of the low-$T$ superfluid density, a signature of dirty d-wave superconductivity, originates from a combined effect in the density of states of `gap filling' and `gap closing'. Finally, we demonstate that the Uemuera plot of $T_c$ vs.\ $\rho_s$ deviates sharply from the conventional Abrikosov-Gor'kov theory for radiation-induced defects in PuCoGa$_5$, but follows the same trend of short-coherence-length high-$T_c$ cuprate superconductors.