Bipolaron kinetics of high-Tc cuprates

Abstract

Based on the generic Hamiltonian including the electron-phonon interaction and the direct Coulomb repulsion the ground state of cuprates is shown to be a charged 2e Bose liquid of small bipolarons if the electron-phonon coupling constant λ is about or larger than 0.5. Hole bipolaron band structure is derived for perovskite lattices. A microscopic theory of the normal state in-plane and c-axis transport of copper oxides is developed. The fundamental relationship between the anisotropy of resistivity and the spin susceptibility is derived. The temperature and doping dependence of the in-plane and out-of-plane resistivity as well as the spin susceptibility are found to be in remarkable agreement with the experimental data in underdoped, optimally and overdoped La 2- xSr xCuO 4 for the entire temperature regime from Tc up to 600 K. The normal state gap is explained and its doping and temperature dependence is clarified. Unusual logarithmic temperature dependence of resistivity at very low temperatures is quantitatively described as well. A new phase diagram of doped cuprates is proposed.