Superconductivity-localization interplay and fluctuation magnetoresistance in epitaxial BaPb$_{1-x}$Bi$_x$O$_3$ thin films

摘要

BaPb$_{1-x}$Bi$_x$O$_3$ is a superconductor, with transition temperature$T_c=11$ K, whose parent compound BaBiO$_3$ possess a charge ordering phase andperovskite crystal structure reminiscent of the cuprates. The lack of magnetismsimplifies the BaPb$_{1-x}$Bi$_{x}$O$_3$ phase diagram, making this system anideal platform for contrasting high-$T_c$ systems with isotropicsuperconductors. Here we use high-quality epitaxial thin films andmagnetotransport to demonstrate superconducting fluctuations that extend wellbeyond $T_c$. For the thickest films (thickness above $\sim100$ nm) this regionextends to $\sim27$ K, well above the bulk $T_c$ and remarkably close to thehigher $T_c$ of Ba$_{1-x}$K$_x$BiO$_3$ ($T_c=31$ K). We drive the systemthrough a superconductor-insulator transition by decreasing thickness and findthe observed $T_c$ correlates strongly with disorder. This material manifestsstrong fluctuations across a wide range of thicknesses, temperatures, anddisorder presenting new opportunities for understanding the precursor ofsuperconductivity near the 2D-3D dimensionality crossover.