Superconductivity-localization interplay and fluctuation magnetoresistance in epitaxial BaPb1-xBixO3 thin films

BaPb1-xBixO3 is a superconductor, with transition temperature T-c = 11 K, whose parent compound BaBiO3 possesses a charge ordering phase and perovskite crystal structure reminiscent of the cuprates. The lack of magnetism simplifies the BaPb1-xBixO3 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 similar to 100 nm) this region extends to similar to 27 K, well above the bulk T-c and remarkably close to the higher T-c of Ba1-xKxBiO3 (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.