Infrared reflectivity of untwinned YBa2(Cu1-xZnx)3O7-δ single crystals

The ab-plane reflectivity of untwinned YBa2(Cu1-xZnx)3O7-δ single crystals is measured between 250 and 20 000 cm-1 at room temperature. Through Zn substitution, the optical conductivity along Eb shows a broad peak at about 2000 cm-1, suggesting localization of the chain band carrier. The conductivity along Ea shows no mid-infrared absorption and slightly decreases from the far- to mid-infrared region through Zn substitution. Analysis of the conductivity along Ea shows that the main effect of Zn substitution is to increase the impurity scattering rate. A small amount of carrier reduction and suppression of effective mass enhancement at low frequency are also observed. The suppression of the effective mass enhancement is discussed by the antiferromagnetic spin-fluctuation theory of Fermi liquid.