Electron energy-loss spectroscopy of the high-temperature superconductor Ba2YCu3O7-x

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Abstract
Electronic transitions in the high-temperature superconductor Ba2YCu3O7-x have been studied over a wide range, using the technique of transmission electron energy-loss spectroscopy in a scanning transmission electron microscope at room temperature. Some variations in peak intensities were observed in the spectra of samples that have been exposed to a high dose of electron beam irradiation and of old samples, which may be related to the loss of oxygen. Combining the energy-loss data with infrared measurements over a lower energy range, Kramers-Kronig analysis was carried out to obtain the dielectric function of the crystal. The optical conductivity curve is interpreted in terms of a triplet of empty conduction band density-of-states maxima which are based mainly on Ba and Yd orbitals.