${\mathrm{BaPb}}_{1-x}{\mathrm{Bi}}_x{\mathrm{O}}_3$ is a superconductor, with transition temperature $T_c=11$ K, whose parent compound ${\mathrm{BaBiO}}_3$ possesses a charge ordering phase and perovskite crystal structure reminiscent of the cuprates. The lack of magnetism simplifies the ${\mathrm{BaPb}}_{1-x}{\mathrm{Bi}}_x{\mathrm{O}}_3$ phase diagram, making this system an ideal platform for contrasting high-$T_c$ systems with isotropic superconductors. Here we use high-quality epitaxial thin films and magnetotransport to demonstrate superconducting fluctuations that extend well beyond $T_c$. For the thickest films (thickness above $\sim 100\mathrm{nm}$) this region extends to $\sim 27\mathrm{K}$, well above the bulk $T_c$ and remarkably close to the higher $T_c$ of ${\mathrm{Ba}}_{1-x}{\mathrm{K}}_x{\mathrm{BiO}}_3$ ($T_c=31$ K). We drive the system through a superconductor-insulator transition by decreasing thickness and find the observed $T_c$ correlates strongly with disorder. This material manifests strong fluctuations across a wide range of thicknesses, temperatures, and disorder presenting new opportunities for understanding the precursor of superconductivity near the 2D-3D dimensionality crossover.

• Received 13 January 2018

DOI:https://doi.org/10.1103/PhysRevMaterials.2.041801