Evidence of local superconductivity in granular Bi nanowires fabricated by electrodeposition

An unusual enhancement of resistance (i.e., a ``superresistivity'') below a certain characteristic temperature Tₛᵣ was observed in granular Bi nanowires. This ``superresistive'' state was found to be dependent on the applied magnetic field as well as the excitation current. The suppression of Tₛᵣ by magnetic field resembles that of a superconductor. The observed superresistivity appears to be related to the nucleation of local superconductivity inside the granular nanowire without long-range phase coherence. The phenomenon is reminiscent of the ``Cooper-pair insulator'' observed previously in ultrathin two-dimensional superconducting films and three-dimensional percolative superconducting films.