Abstract
X-ray absorption spectra on the overdoped high-temperature superconductors and reveal a striking departure in the electronic structure from that of the underdoped regime. The upper Hubbard band, identified with strong correlation effects, is not observed on the oxygen edge, while the lowest-energy prepeak gains less intensity than expected above . This suggests a breakdown of the Zhang-Rice singlet approximation and a loss of correlation effects or a significant shift in the most fundamental parameters of the system, rendering single-band Hubbard models inapplicable. Such fundamental changes suggest that the overdoped regime may offer a distinct route to understanding in the cuprates.
- Received 21 April 2009
DOI:https://doi.org/10.1103/PhysRevLett.103.087402
©2009 American Physical Society