Superconductor-insulator transition driven by local dephasing

We consider a system where localized bound electron pairs form an array of ``Andreev''-like scattering centers coupled to a fermionic subsystem of uncorrelated electrons. By means of a path-integral approach, that describes the bound electron pairs within a coherent pseudospin representation, we derive the effective action for the collective phase modes that arise from the coupling between the two subsystems once the fermionic degrees of freedom are integrated out. This effective action has features of a quantum phase model in the presence of a Berry phase term and exhibits a coupling of phase fluctuations to those of the density of bound pairs and the amplitude of the fermion pairs. Due to the competition between the local and the hopping-induced nonlocal phase dynamics it is possible, by tuning the exchange coupling or the density of the bound pairs, to trigger a transition from a phase-ordered superconducting to a phase-disordered Mott insulating state. We discuss the different mechanisms that control the occurrence and eventual destruction of phase coherence both in the weak and strong coupling limit, restricting ourself to homogeneous phases.