Electron energy loss studies of the new high‐Tc superconductor Bi4Ca3Sr3Cu4O16+x

Electron energy loss spectroscopy has been extensively used to investigate the electronic properties of high‐Tc superconductors. In particular, we identified surface and bulk plasmon modes of 1‐2‐3 materials, and a number of peaks related to quasi‐optical transitions. Together with photoemission spectra illustrating the initial states, these peaks provide information on the empty electron states of these materials. We recently extended these studies to sintered and single crystal specimens of the new high‐Tc superconductor Bi4Ca3Sr3Cu4O16+x. There is an overall correlation between the energy loss spectral features and the photoemission features of this material. Specifically, we can explain almost all of the energy loss features by assuming that they are due to quasi‐optical transitions to two groups of empty states. 0.5–1.1 eV and 1.5–2 eV above the Fermi edge. This analysis does not explain all the peaks, and in particular those related to collective electron modes. The identification of the bulk plasmo...