Optical studies of charge dynamics in the optimally-doped Bi2212 and the non-superconducting cobaltate single crystals

An analysis of the frequency-dependent scattering rate reveals signatures of the superconducting gap as well as the pseudogap in high-T_c cuprates. These features can be identified in the temperature-dependent spectral function W(omega), inverted from the optical data of the optimally-doped Bi2212 using an experimentally unambiguous method that shows the behavior of both the maxima and minima in the spectral function.