ar X iv : c on d - m at / 9 60 70 98 v 1 1 4 Ju l 1 99 6 Coherent ‘ ab ’ and ‘ c ’ transport theory of high - T c cuprates

We propose a microscopic theory of the 'c'-axis and in-plane transport of copper oxides based on the bipolaron theory and the Boltzmann kinetics. The fundamental relationship between the anisotropy and the spin susceptibility is derived, ρ c (T, x)/ρ ab (T, x) ∼ x/ √ T χ s (T, x). The temperature (T) and doping (x) dependence of the in-plane, ρ ab and out-of-plane, ρ c resistivity and the spin susceptibility, χ s are found in a remarkable agreement with the experimental data in underdoped, optimally and overdoped La 2−x Sr x CuO 4 for the entire temperature regime from T c up to 800K. The normal state gap is explained and its doping and temperature dependence is clarified. The absolute value and qualitatively different temperature dependence of the in-plane and c-axis resistivity [1] as well as the normal state gap observed with NMR, neutron scattering, thermodynamic and kinetic measurements in copper based high-T c oxides are recognised now as the key to our understanding of the high-T c phenomenon [2,3]. By the use of the room-temperature values of the ab and c-axis conductivities of the prototypical