Abstract

Optical and infrared absorption and photoinduced absorption studies of the high T_c families of materials give insight into the types of charged excitation existing in these materials, as well as the nature of their ground states and mechanisms for superconductivity. Near steady state photoinduced optical absorption spectra on thin films and pressed KBr pellets of YBa₂- C_U3O_7-δ for δ ~ 0.7 show two absorption peaks below ~1.5 eV and a crossover to photoinduced bleaching at higher energies. Photoinduced infrared spectra reveal several absorption and bleaching modes and a broad electronic transition centered at ~1000 cm^-1. The photoinduced bleaching modes correspond to direct absorption modes of the semiconducting YBa₂Cu₃O_6.3 material. The photoinduced absorption modes correspond to direct absorption modes of the superconducting YBa₂Cu₃O₇ material. The presence of the photoinduced IR modes and the higher lying absorptions and bleachings shows that long-lived, stable electronic defect states lying within the energy gap are created.

© 1989 Optical Society of America