Interlayer tunnel and thermal activation in c-axis transport in Bi2Sr2CaCu2O8+delta

We present a phenomenological model for the electrical transport in double-layered cuprates, based on the existence of two energy barriers along the c-axis. The model is applied to measurements of the de resistivity in Bi2Sr2CaCu2O8+delta single crystals. We find that the model gives a comprehensive description of the out-of-plane normal resistivity rho(e) at various doping delta. Once the normal state has been determined, it is possible to obtain the fraction eta(T, delta) of the carriers that, below the pseudogap temperature T*, do not participate to the c-axis conductivity. We find that all the curves eta(T, delta) collapse onto a single universal curve eta[T/T*(delta)]. (c) 2007 Elsevier B.V. All rights reserved.