X-ray absorption spectra reveal the inapplicability of the single-band Hubbard model to overdoped cuprate superconductors.
X-ray absorption spectra on the overdoped high-temperature superconductors Tl2Ba2CuO(6+delta) and La(2-x)SrxCuO(4+/-delta) 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 K edge, while the lowest-energy prepeak gains less intensity than expected above p approximately 0.21. 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.
Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan. dpeets@scphys.kyoto-u.ac.jp
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Peets
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Hawthorn
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Shen
Young-June
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Kim
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Zhang
Seiki
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Komiya
Yoichi
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Ando
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Sawatzky
Ruixing
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Liang
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