CONDUCTANCE FLUCTUATIONS IN MESOSCOPIC GRANULAR SUPERCONDUCTORS

We report on a transport study of granular superconductivity films wit h lengths as small as 1000 Angstrom and typical grain sizes of 100 Ang strom. The I-V characteristics of these samples are hysteretic and exh ibit sharp, discontinuous voltage jumps. We attribute these features t o destruction of superconducting phase locking between individual grai ns. In addition, we observe a rich profile of conductance fluctuations which, unlike the previous features, are non-hysteretic. The amplitud e of the fluctuations scales with the conductance and may reach values much larger than e(2)/h. We suggest that these features stem from int erference of the superconductive wave-function, which is modulated by self induced flux penetrating the random granular network. (C) 1998 El sevier Science Ltd. All rights reserved.