Correlation of the local and the macroscopic properties of high-temperature superconductors: EXAFS data analysis.

Based on temperature-dependent EXAFS studies of Ba(1-x)K(x)BiO(3) superconducting oxide, a model of the relationship between the local crystal and the local electronic structures has been proposed. Oxygen ions were found to vibrate in a double-well potential and their vibrations are correlated with the local electron pair transfer due to the dynamical exchange BiO(6) <--> BiL(2)O(6), where L(2) denotes the hole pair in the antibonding Bi 6s O2p(sigma*) orbital of the octahedral complex. The similarity of the EXAFS spectra features of Ba(1-x)K(x)BiO(3) and La(2-x)Sr(x)CuO(4) allowed us to propose a similar model for Cu-based superconducting oxides. The model, in a common approach, explains the antiferromagnetic state, metal-insulator phase transition and the appearance of superconductivity at Sr(2+) doping of La(2)CuO(4), and eliminates discrepancy between the neutron-scattering and EXAFS data.