PHONONS AND ELECTRON-PHONON INTERACTION IN HIGH-TC SUPERCONDUCTORS

The phenomenon of high T(c) superconductivity and its present status is briefly reviewed. Electron-phonon interaction seems to play a role in the superconducting pair formation, although it does not suffice to account for the highest T(c) reached (congruent-to 130 K). A review of the optically active (Raman and ir) phonons is presented using YBa2Cu3O7 (T(c) = 92 K) as a paradigm, with particular emphasis on electron-phonon coupling phenomena. Observed changes in phonon frequencies, widths and spectral strengths near T(c) are discussed. Some consideration is given to the coupling of the phonons with crystal field levels in NdBa2Cu3O7. Resonant Raman profiles are also discussed and compared with theoretical predictions.