Extensive study of the optical spectra for high-temperature superconducting oxides and their related materials from the infrared to the vacuum-ultraviolet energy region

• DOI: 10.1364/josab.6.000475
• Publication Date: 2008-12-01T15:36:51Z
• Authors: S. Tajima; M. Seki; Y. Hidaka; K. Oka; H. Unoki; M. Suzuki; S. Suga; H. Ishii; T. Nakahashi; T. Murakami; T. Takagi; S. Uchida
• Keywords: Isostructural; Ultraviolet

Optical reflectivity spectra of (La, Sr)2CuO4 and YBa2Cu3Oy have been measured over a wide spectral range as high 40 eV. Although overall features the observed are explained well by results available band calculations, differ significantly from calculation in low-energy region below 5 eV, where spectrum would presumably be dominated transitions between states involving Cu 3d O 2p or charge-transfer (CT) excitation states. In contrast to calculation, absorption that probably corresponds Cu–O CT process is weak broad, even for insulating La2CuO4; thus we cannot firmly determine energy characterizes electronic these cuprates. To estimate this parameter, cuprates compared with those isostructural Sr)2MO4 (with M = Ni, Co, Fe) A-site-substituted Nd2CuO4. From also measurement anisotropy respect planes, 2–4 eV both cuprate superconductors. This value larger than predicted theory, indicating breakdown great modification picture region.