Absence of Quantum Metallic Behavior in Disordered Granular Superconductors

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We examine the idea, postulated by Phillips et al., that a finite resistivity in T → 0 limit in disordered granular superconducting (SC) films is explained as a consequence of the absence of phase stiffness in a phase glass (PG) peculiar to granular systems. It is found that a coupling between the nonzero PG order and the ordinary SC fluctuation makes the conductivity divergent. However, an actual drop of resistivity is argued to occur due to another SC glass ordering, induced by the precursory PG fluctuation, corresponding to the vortex-glass transition in a nonzero magnetic field.