Possibility of the vortex-antivortex transition temperature of a thin-film superconductor being renormalized by disorder

The universal relation between the Kosterlitz-Thouless transition temperature $T_c$ and the superfluid sheet density of thin-film superconductors with mean-field transition temperature $T_{c0}$ results in a monotonically decreasing dependence of the ratio $T_c$/$T_{c0}$ on the normal-state sheet resistance $R_n$. Ambiguity in the experimental definition of $R_n$ in highly disordered thin-film superconductors is addressed by reexamining previously published data on amorphous composite In/${\mathrm{InO}}_{\mathrm{x}}$ films. Arguments are presented in favor of using the zero-temperature value of $R_n$, a quantity obtained by extrapolation. The dependence of $T_c$/$T_{c0}$ on $R_n$ that results from such a choice is in agreement with theory for dirty superconductors and thus suggests that additional corrections to $T_c$ in the presence of extreme disorder are not required.