Electron correlation and charge transfer in superconducting superlattices.
We use x-ray spectroscopy to examine the electronic structure of high-temperature superconducting superlattices [(Ba0.9Nd0.10)CuO(2 + delta)]2/[CaCuO2]2. The O 2p density of states reveals the insulating character of the individual component layers and the metallic character of the superlattices. We report the first direct observation of Zhang-Rice singlets in artificial high-temperature superconducting heteroepitaxial structures. The experimental findings in the superlattices and its component layers offer evidence of charge transport from the so-called charge reservoir layer to the superconducting infinite layer. This suggests a strong link between superconductivity and both electron correlation and charge transfer within the superlattices.
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. bkfreelon@lbl.gov
B
B
Freelon
A
A
Augustsson
J-H
JH
Guo
P G
PG
Medaglia
A
A
Tebano
G
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Balestrino