Two-component model for optical conductivity in Y-Ba-CuO superconductors

Abstract

The optical conductivity of optimized doped YBa2Cu3O7-δ (δ=0·0,T c=92 K) superconductors, which are frequency dependent, has been theoretically investigated based on two-component (Drude and mid infrared terms) approach within the Fermi liquid description. Our approach incorporates the Drude contribution as well as hopping of charge carriers in the model dielectric function along with the structure factor. It explains the anomalies observed in the optical measurements for the normal state as the frequency dependence of optical conductivity using the Drude term which gives a sharp peak at zero frequency, and a long tail at higher frequencies, i.e. in the infrared region. The extra term (hopping carriers) gives a peak value in the optical conductivity centred in the mid infrared region. The two species of charge carriers contribution to the conduction in the CuO chain layer as well as CuO2 layer will account for the optical conductivity in the mid infrared as well as infrared frequency regions. The analysis reveals an interesting relation\(\sigma _{CuO_2 layer} \approx 3\sigma _{chain layer} \), and the nature for optical conduction with energy is similar qualitatively, the only difference is quantitatively. It is shown that the analysis is consistent with the published data on optical conductivity in optimized-doped YBa2Cu3O7-δ superconductors.