Coherent ab and c Transport Theory of High-Tc Cuprates.

Abstract

We propose a microscopic theory of the normal state transport in copper oxides based on the bipolaron theory which describes qualitatively the temperature $(T)$ and doping $(x)$ dependence of the in-plane ${\ensuremath{\rho}}_{\mathrm{ab}}$ and out-of-plane ${\ensuremath{\rho}}_{c}$ resistivity and the spin susceptibility ${\ensuremath{\chi}}_{s}$ in underdoped, optimally doped, and not very heavily overdoped ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ for the temperature range from ${T}_{c}$ up to 600 K. A free parameter relation between the anisotropy and the spin susceptibility is derived, ${\ensuremath{\rho}}_{c}(T,x)/{\ensuremath{\rho}}_{\mathrm{ab}}(T,x)\ensuremath{\sim}{x/T}^{1/2}{\ensuremath{\chi}}_{s}(T,x)$, which agrees quantitatively with the experiment. The normal state gap is explained and its doping and temperature dependence clarified.