Abstract
Small-polaron and bipolaron formation destroys the Fermi-liquid behaviour of carriers strongly coupled with phonons or spin fluctuations. The non-adiabatic motion of self-trapped carriers results in the fundamental difference of low-mobility conductors compared with simple metals and Bardeen-Cooper-Schrieffer supercondutors. An appealing explanation of many properties of high-Tc cuprates and doped fullerenes emerges if one applies the polaron theory of strong-coupling superconductivity. The microscopic theory of the in-plane and ‘c’-axis transport in cuprates is proposed. The temperature and doping dependence of the in-plane and out-of-plane resistivity, the Hall effect and the spin susceptibility is shown to be in a remarkable agreement with the experimental data in underdoped, optimally doped and overdoped La2-xSrxCuO4 for the entire temperature regime. The normal state gap is explained and its doping and temperature dependence is clarified. The resonance Wigner scattering of small bipolarons in a random potential leads to logarithmically divergent low-temperature resistivity as observed for several cuprates. The interaction responsible for high Tc values is elucidated.