SUPERCONDUCTOR-INSULATOR TRANSITION IN DISORDERED BOSON-SUPERLATTICES

We calculate the transport properties of a disordered Bose condensate. A superlattice made from two-dimensional planes of bosons in the condensate phase is considered. The disorder is due to charged impurities. We consider a homogeneous distribution of impurities and also impurities randomly distributed in planes. The dispersion relation of the collective excitations (plasmons) for the clean boson superlattice is calculated. The disorder induced phase transiton from a superfluid phase to an insulator phase is discussed and the static conductivity (σc) at the transition point is expressed in terms of the microscopic parameters of the model. For strongly coupled planes we find that σc is of order e2/h. The relation of our theoretical results to experiments with high-temperature superconductors is discussed. © 1990 Springer-Verlag.