Abstract
Hard x-ray photoemission spectroscopy (PES) of Cu core electronic states, with a probing depth of , is used to show that the Zhang-Rice singlet feature is present in but is absent in . Hole and electron doping in (LSCO) and (NCCO) result in new well-screened features which are missing in soft x-ray PES. Impurity Anderson model calculations establish screening from doped states as its origin, which is strongly suppressed within 15 Å of the surface. Complemented with x-ray absorption spectroscopy, the small chemical-potential shift in core levels () are shown to be consistent with modifications of valence and conduction band states spanning the band gap () upon hole and electron doping in LSCO and NCCO.
- Received 26 January 2005
DOI:https://doi.org/10.1103/PhysRevLett.95.177002
©2005 American Physical Society