ABSTRACT
Presently, the thallium cuprate superconductors have the highest superconducting transition temperatures, up to 125 K, of all known high-temperature superconductors. For infrared studies it is important to have well-defined material, a condition, of course, for all studies, and furthermore to have high-quality material near the surfaces within a range of the penetration depth of the infrared radiation which is about a London penetration depth. Nevertheless, the presently available results of infrared studies are interesting enough to be presented in a comprehensive article. This chapter describes characteristic infrared property of thallium cuprate superconductors. The optical constants that follow from a Kramers-Kronig transformation of reflectivity data for polycrystalline material correspond to effective values that should be discussed by an effective medium theory.
