Valence-electron states of YBa sub 2 Cu sub 3 O sub 7 minus. delta. characterized by combined x-ray and photoemission studies

Journal Article · Thu Mar 01 04:00:00 EST 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.4050· OSTI ID:7142666

Draeger, G; Werfel, F ^[1]; Leiro, J A ^[2]

---

1. Sektion Physik der Martin-Luther Universitaet, Halle-4010, German Democratic Republic (DD)
2. 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), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:7; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
BINDING ENERGY
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
ELECTRONS
ELEMENTARY PARTICLES
ENERGY
ENERGY-LEVEL DENSITY
FERMIONS
IONIZING RADIATIONS
LEPTONS
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
RADIATIONS
SPECTROSCOPY
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
ULTRAVIOLET RADIATION
VALENCE
X RADIATION
YTTRIUM COMPOUNDS
YTTRIUM OXIDES