ELECTRONIC STATES AND OPTICAL-SPECTRA OF HTSC WITH ELECTRON PHONON COUPLING

It is shown that due to the strong electron-phonon interaction the usual Fermi-liquid description of the electron system is violated in the normal phase of HTSC metals (T > T(c)). As a result it is impossible to use the simple formulas of the Drude type for the calculation of FIR properties of the HTSC materials. The many-body calculation of the reflectivity gives a good agreement with the FIR measurements for the single-domain crystal. The processing of the obtained results by using the "extended Drude formula" gives the effective scattering rate 1/tau* almost-equal-to beta-hBAR-omega where beta is about 1 up to 2000 cm-1 (and even for higher frequencies taking into account the interband transitions).