QUANTUM PERCOLATION AND CHARGE TRANSPORT IN HIGH T_c 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 p U(T 0 ) T e ° where T 0 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.