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Electronic Structure of TlBa2CaCu2O(7-Delta)The core levels of TlBa2CaCu2O(7-delta) (Tl-1212) epitaxial films have been measured with X-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level (E(sub F)) for the stoichiometric compound (delta = 0.5), while for 50% oxygen vacancies in the Tl-O layer (delta = 0.5) E(sub F) is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher T(sub c), consistent with a shift of E(sub F) closer to the VHS. Comparisons are made to the core levels and valence bands of Tl2Ba2CaCu2O(8 + delta)(Tl-2212) and HgBa2CaCu2O)6 + delta) (Hg- 1212). The similarity of the Cu 2p(sub 3/2) spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu 2p(sub 3/2) signals exhibit differences which suggest that the replacement of T(sup 3+) with Hg(sup 2+) results in a decrease in the O 2p right arrow Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl,Hg) 6s/5d partial densities of states.
Document ID
19990008055
Document Type
Reprint (Version printed in journal)
Authors
Vasquez, R. P. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Novikov, D. L. (Northwestern Univ. Evanston, IL United States)
Freeman, A. J. (Northwestern Univ. Evanston, IL United States)
Siegal, M. P. (Sandia National Labs. Albuquerque, NM United States)
Date Acquired
August 19, 2013
Publication Date
June 1, 1997
Publication Information
Publication: Physical Review B (Condensed Matter)
Volume: 55
Issue: 21
ISSN: 0163-1829
Subject Category
Solid-State Physics
Funding Number(s)
CONTRACT_GRANT: NSF DMR-91-20000
CONTRACT_GRANT: DE-AC04-94AL-85000
Distribution Limits
Public
Copyright
Other