Oxygen stoichiometry and the electronic structure of high-temperature superconductors

The oxygen content determines the transport properties of Ba2YCu3O7+x and EuBa2Cu3O7+x, and in particular their superconducting behavior at high temperatures. The authors studied the changes in the Ba2YCu3O7+x electronic structure which are caused by modifications in the amount of oxygen. The modifications were achieved either by thermal annealing or by exposure to `white' synchrotron radiation which causes oxygen desorption, with similar results. They found that the decrease in oxygen content affects the line-shape of the upper valence band features and the relative intensity of the Cu satellite features. The lineshape changes simplify the identification of oxygen-related features in the upper valence band region. The exposure to `white' synchrotron radiation of Ba2EuCu3O7+x did not produce similarly large spectral change