Photoemission Spectroscopic Study Of Copper-Oxide Superconductors And Related Materials

The electronic structure of high-Tc superconductors and related materials is studied by photoemission spectroscopy and Bremsstrahlung Isochromat spectroscopy. In the solid solution (La,Sr) 2 CuO 4 , (Nd,Ce) 2 CuO 4 , and (La,Sr) 2 NiO 4 systems, the valence band spectra do not shift as a function of the doping concentration, which suggests that E F is pinned by the states within the charge-transfer gap and that the rigid band description is not appropriate in considering the metal-insulator transition in these systems.