Valence-electron states of YBa sub 2 Cu sub 3 O sub 7 minus. delta. characterized by combined x-ray and photoemission studies
- Sektion Physik der Martin-Luther Universitaet, Halle-4010, German Democratic Republic (DD)
- Department of Physical Sciences, University of Turku, SF-20500 Turku, Finland (FI)
X-ray-emission (XES), x-ray-excited photoelectron (XPS), and ultraviolet-excited photoelectron spectra of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} have been measured and arranged on a common binding-energy scale by XPS core lines. Three main valence-band (VB) structures at 2.7, 3.7, and 4.8 eV relative to the Fermi level ({ital E}{sub {ital F}}=0) could be identified representing hybridized Cu 3{ital d}/4{ital p}--O 2{ital p} states. The VB XES and photoelectron spectra are strongly influenced by correlation and charge-transfer effects and hence reproduce the density of states (DOS) of excited multiple-hole states but not the one-hole ground-state DOS. These processes are responsible for the observed differences between high-energy spectroscopic results and one-electron theory. From the XES compared with calculations we estimate a local partial correlation shift'' of the theoretical Fermi level ({Delta}{ital E}{sub {ital F}}s/r{sup {ital c}{ital o}{ital r}{ital r}}) in the energy range 0.6--1.6 eV. Charge transfer and screening processes contribute to the x-ray transitions of the selective-type Cu 2{ital pd}{sup 10}{ital L}{r arrow}{ital d}{sup 9}{ital L} and O 1{ital sp}{sup 6}Cu 3{ital d}{sup 9}{r arrow}{ital d}{sup 9}{ital L} owing to Cu {ital L}{alpha} and O {ital K}{alpha}, respectively. With the mechanism of charge transfer and band shift acting in highly correlated electron systems, such as high-temperature superconducting compounds, a possible explanation for the unusually low DOS at {ital E}{sub {ital F}} in excitation spectra is given.
- OSTI ID:
- 7142666
- Journal Information:
- Physical Review, B: Condensed Matter; (USA), Vol. 41:7; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM OXIDES
ENERGY-LEVEL DENSITY
COPPER OXIDES
YTTRIUM OXIDES
BINDING ENERGY
ELECTRONS
PHOTOELECTRON SPECTROSCOPY
SUPERCONDUCTORS
ULTRAVIOLET RADIATION
VALENCE
X RADIATION
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
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FERMIONS
IONIZING RADIATIONS
LEPTONS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
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