Rigid band behavior of Nd_2-xCe_xCuO_4-y: A direct and inverse photoemission study

We have employed ultraviolet photoemission spectroscopy at hν = 21.2 and 40.8 eV and inverse photoemission spectroscopy at hν = 9.5 eV to study Nd2-xCexCuO4-y (x = 0.0, 0.1, 0.15, 0.2). We observe a shift of the Fermi level to higher energies as a function of x. The total shift is 0.3 eV and saturates at x = 0.2. As suggested by existing band-structure calculations, this result seems to point to a rigid-band filling of the Ce-derived electrons in these "electron-doped" superconducting cuprates. © 1990.