Raman Investigations on the Y-Ba-Cu-O-System
The discovery of ceramic perovskites with superconductivity above 20K1 and 80K2 started a new discussion about the superconducting mechanism. Whether the new ceramic superconductors can be described within an ordinary BCS- or Eliashberg-formalism, or more exotic mechanisms as solitons, polarons or excitons are responsible for the superconductivity, is the most interesting question. Raman scattering is based on the electron-phonon interaction, and, therefore, can sensitively probe properties of the pure electronic and phonon states together with their interaction. Because of the long wavelength (compared to interatomic distances) of the photons, this method is restricted to investigations of the centre of the Brillouin-zone, therefore, one can not assume to observe the superconducting mechanism directly. However, important properties as, e.g., the superconducting gap, can in principle be measured3,4. In addition, changes in the Raman spectrum due to structural changes or composition of the material in comparison with the change of superconducting properties will give valuable information about the intrinsic properties of the material. This information is needed for an understanding of the superconducting behaviour5.
KeywordsRaman Spectrum Phonon Frequency Electronic Band Structure White Phase Ceramic Superconductor
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