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 changes