Normal-State Optical Features Study of Nd123 and Gd1212 HTSC Materials for Photonics and Metamaterials Fabrication

YBCO-like Nd123 and Gd1212 superconductors in the normal state, in the visible and infrared regime, have been analyzed in this work. Superconductors, particularly high-temperature superconductors (HTSCs), hold indeed a great interest in the highly innovative research field of metamaterials and photonics with important applications. Indeed nanostructured devices suffer from increasing resistivity with frequency in metals, and superconducting materials provide a viable route to approach this problem. Moreover, HTSCs are plasmonic materials at nonzero temperature, and their features, not available in conventional materials, make them very attractive for metamaterials use. In particular, we investigate Nd123, for its high T-c, and Gd1212, for the coexistence, in its unitary cell, of magnetic order and superconductivity. Samples were extracted from top-seeded melt-textured growth bulk pellets and bars. Fourier transform infrared spectroscopy analysis, performed in the far-infrared, shows articulated peak structures with k < k(min) and a plateau for higher k, allowing for Nd123 and Gd1212 pseudogap measurement. Raman spectroscopy and microscopy provided a structural mapping of our Nd123 samples, allowing for distinguishing the superconducting matrix from nonsuperconducting phase inclusions (precipitates) and providing an instrument to discriminate among optical responses of the different compounds.