c-axis transport and phenomenology of the pseudogap state in Bi2Sr2CaCu2O8+delta

We measure and analyze the resistivity of Bi2Sr2CaCu2O8+delta crystals for different doping delta. We obtain the fraction of carriers eta(T,delta)=n(g)/n(tot) that do not participate in the c-axis conductivity. All the curves eta(T,delta) collapse onto a universal curve when plotted against a reduced temperature x=[T-Theta(delta)]/Delta(*)(delta). We find that at the superconducting transition n(g) is doping independent. We also show that a magnetic field up to 14 T does not affect the degree of localization in the (a,b) planes but widens the temperature range of the x scaling by suppressing the superconducting phase coherence.