Influence of actual structure on the luminescence of high-temperature superconductors

Though the luminescence of high-temperature superconductors (HTSC) came to be studied just after the discovery of high-temperature superconductivity, the problem of identification of the intrinsic emission of these compounds has not yet been resolved. This is due, first of all, to the fact that the luminescent properties of HTSC are influenced both by intense light irradiation and the environment. Previously such consideration has been given to interpretation of the luminescence band with a maximum at 2.8 eV typical of copper-oxide HTSCs. The goal of the present study is to elucidate the nature of the luminescence band with a maximum at 2.4 eV. The authors have investigated the luminescence spectra of single crystals and polycrystals (ceramics) of HTSC samples of YBa2Cu3O7-δ (YBaCuO), ceramic samples of YBa2Cu4O8, and ceramic and monocrystalline Bi-based HTSC samples. Moreover, the influence of mechanical and chemical treatment of their surfaces, and intense light irradiation on the luminescent properties of the actual structure of the samples was studied