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Optical Excitations in CuO2 Sheets With and Without Electron Doping: Relevance to Superconductivity Produced by Electron Doping

  • Y. Tokura
  • H. Takagi
  • S. Kosihara
  • S. Uchida
Conference paper
Part of the Springer Series in Solid-State Sciences book series (SSSOL, volume 89)

Abstract

Optical excitations, in particular charge-transfer(CT) excitons, plasmons and two-magnon excitations, have been investigated spectroscopically for single crystals of prototypical cuprate compounds with single-layer Cu-O sheets and chains. In all crystals investigated (for example Nd2CuO4, CaCuO2, Ca2CuO3, Sr2CuO2Cl2 and etc.), the strong CT transtion from O-2p to Cu-3d is observed at 1.5–1.9eV and its anisotropy depending on the Cu-O network is quite evident. Together with results of two-magnon Raman scattering and magntetic susceptibility, analysis of these optical data enables us to evaluate the values of fundamental physical parameters for Cu-O sheets(e.g. transfer energy, CT gap and exchange energy) as well as their depedence on the Cu-O network and dimension. To investigate change of electronic states upon electron-doping in CuO2 and its relevance to electronsuperconcductivity, reflectance spectra of single crystals of Ce-doped Nd2CuO4 have been measured in the wide electron-concentration range where the compound undergoes the phase change from the CT insulator to nonsuperconducting metal through the high-Tc superconductor.

Keywords

Transfer Energy Electronic State Magnetic Material Phase Change 2Engineering Research 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Copyright information

© Springer-Verlag Berlin, Heidelberg 1989

Authors and Affiliations

  • Y. Tokura
    • 1
  • H. Takagi
    • 2
  • S. Kosihara
    • 1
  • S. Uchida
    • 2
  1. 1.Department of PhysicsUniversity of TokyoTokyo 113Japan
  2. 2.Engineering Research InstituteUniversity of TokyoTokyo 113Japan

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