Photoemission spectral weight distribution in Y{sub 1{minus}{ital x}}Ca{sub {ital x}}TiO{sub 3}
- Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113 (Japan)
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113 (Japan)
We have studied Y{sub 1{minus}{ital x}}Ca{sub {ital x}}TiO{sub 3} by photoemission and inverse-photoemission spectroscopy. Valence-band photoemission spectra show a {ital d}-band peak {approximately}1.4 eV below the Fermi level ({ital E}{sub {ital F}}), which evolves into the lower Hubbard band in the {ital x}= 0 ({ital d}{sup 1}) limit. The spectra show quasiparticle emission at {ital E}{sub {ital F}} with an extremely small spectral weight, {ital z}{approximately}0.01, which vanishes as the system approaches either the Mott insulator limit ({ital x}=0) or the band insulator limit ({ital x}=1). Correspondingly, inverse-photoemission spectra show the upper Hubbard band and a quasiparticle feature in the unoccupied state. The fact that the observed quasiparticle spectral weight is smaller than that of La{sub 1{minus}{ital x}}Sr{sub {ital x}}TiO{sub 3} is attributed to the larger {ital U}/{ital W}, where {ital U} is the on-site {ital d}-{ital d} Coulomb energy and {ital W} is the {ital d}-band-width. The presence of the {approximately}1.4-eV peak for a nearly empty {ital d} band ({ital x}{approximately} 1) and the small spectral weight at {ital E}{sub {ital F}} cannot be explained within the Hubbard model, indicating the importance of interactions which are not included in the model, such as the long-range Coulomb interaction and the electron-phonon interaction. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 383821
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 54, Issue 12; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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