QUANTUM PERCOLATION AND CHARGE TRANSPORT IN HIGH Tc SUPERCONDUCTORS

Abstract

We have investigated the consequences of internal fields on transport properties in insulators close to a metal-insulator-superconductor transition. An interpolation formula for the resistivity as a function of temperature describing insulating, metallic and superconducting regimes has been deduced in the framework of a quantum percolation model in which hopping processes on localised states occur. The contribution to the internal fields on carriers has been taken into account up to quadrupole terms. The resistivity follows a law ρ ∪(T0)δ T e(T0/T)1/2 where T0 corresponds to a coulomb gap and exhibits anisotropic quadrupole angular dependence, suggesting a correlation with the pseudo-gap observed in superconductors in the underdoped regime.