High T-c superconductors for plasmonics and metamaterials fabrication: A preliminary normal state optical characterisation of Nd123 and Gd1212

The application of metamaterials and plasmonic structures in the visible and near infrared are strongly limited by the dissipative losses due to the low conductivity of the most used metals in this frequency range. High temperature superconductors are plasmonic materials at nonzero temperature that can provide a possible alternative approach to overcome this limit. Moreover, they can have zero or even negative dielectric constant, and a bipolar behavior. All these characteristics are attractive for plasmonic applications, and encourage further studies aimed at a more detailed knowledge of the parameters characterizing high temperature superconductors as possible optical materials. In this paper, Fourier Transform Infrared Spectroscopy analysis and ellipsometric measurements in the visible and infrared spectral regions on NdBa2 Cu 3O7-? (Nd123) and ruthenocuprate superconductor GdSr2RuCu2O8-? (Gd1212) are reported. As a matter of fact, Nd123 presents the highest transition temperature (Tc = 96 K) and the most interesting magnetic response properties among YBCO-like cuprate superconductors, whereas the coexistence in the same cell of superconductivity and magnetic order below Tc in Gd1212 can be an interesting feature for next metamaterial-like applications. The obtained results confirm the promising features of the considered materials.