SPECTROSCOPIC STUDY OF THE ELECTRONIC STATES OF SINGLE-CRYSTAL CUGEO3

The electronic states of CuGeO3 that exhibit a spin-Peierls transition at 14 K were investigated by optical reflectivity and photoemission measurements. A quantitative analysis of the charge-transfer excitation has revealed that the p-d hybridization energy between Cu and O for CuGeO3 is about half of that for La2CuO4. Thus CuGeO3 has a much narrower pd band than high-Tc cuprates, which makes carrier doping difficult in this system. The photoemission measurement also suggests the small p-d transfer energy. © 1995 The American Physical Society.