Abstract
The spin nature of the states at the top of the valence band in and has been investigated with spin polarized resonant photoemission. A clear Zhang-Rice singlet state is observed at the top of the valence band in the undoped compound showing that the parent compound of this electron doped superconductor is similar to the parent compounds of hole doped cuprate superconductors. Upon doping, the stability of the singlet is destroyed and the optimum doped compound does not display any well-separated singlet state. These results indicate that hole contribution to the superconductivity in this system is not important in contrast to what has previously been suggested on the bases of transport measurements.
- Received 8 January 2003
DOI:https://doi.org/10.1103/PhysRevB.67.100501
©2003 American Physical Society