INFRARED CONDUCTIVITY IN THE NORMAL-STATE OF CUPRATE THIN-FILMS

This paper summarizes the main features of the infrared conductivity s pectra in the 500-7000 cm(-1) range derived from room-temperature refl ectivity measurements performed on a variety of thin films (YBa2Cu3O7, BiSrCaCuO). The conductivity of these samples decreases with frequenc y as a power law with an exponent similar to 0.7, and the scattering r ate increases linearly with frequency. A detailed comparison with the conductivity for the marginal Fermi liquid (Abrahams, Littlewood, and Varma) and for the Luttinger liquid (Anderson) is performed. In the fo rmer case, the effect of temperature appears crucial even in this ener gy range (omega greater than or equal to T) and allows one to achieve satisfactory fits. In the latter case, both the conductivity and the s cattering rate may be accounted for by a single parameter.