FAR-INFRARED STUDY OF THE INTERPLANE CHARGE DYNAMICS IN HIGH-Tc SUPERCONDUCTING CUPRATES

The c-axis optical spectra have been investigated over wide T- and omega-ranges for typical high-T-c superconductors ( HTSC), Bi2Sr2CaCu2O8 and YBa2Cu3O gamma Comparing the spectra of different HTSC. it was found that the anisotropy ratio is strongly affected by the nature of the blocking layers such as the BiO-layers and the CuO-chains. However, the low dimension in this material cannot be represented only by an anisotropy ratio which is dominated by a structural factor. Even in the weakly anisotropic material such as the overdoped YBCO. the carrier confinement feature is revealed in the normal and the superconducting states by a large scattering rate and a dirty-limit like superconductivity along the c-axis. The anomalous conduction in the c-direction is well characterized by the conductivity suppression at low frequencies which is responsible for a semiconducting temperature dependence of the dc resistivity. The critical temperature and frequency for this conductivity suppression strongly depend on the doping level, being suggestive for the peculiar mechanism of the c-axis conduction.