On the Metal-Insulator Transitions in VO_2 and Ti_2O_3 from a Unified Viewpoint

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Author(s)

Abstract

The metal-insulator (M-I) transitions in VO_2 and Ti_2O_3 were investigated using the three-band Hubbard model in connection with the on-site exchange interaction and lattice distortions. Although these two compounds have different crystal structures, the mechanism of the phase transitions can be understood from a unified viewpoint; an increase in energy level separation among the f_<2g> orbilals caused by the lattice distortion triggers an abrupt change in the electron configuration in doubly occupied sites from an S = 1 Hund's coupling state to a low-spin S = 0 state with much largerenergy and this strongly suppresses the charge fluctuation, resulting in localization of electrons. These M-I transitions are not induced by an increase in relative strength of the Coulomb interaction against the electron hopping as in the conventional scenario of the Mott-Hubbard transition but by the level splitting among the f_<2g> orbitals against the on-site exchange interaction. Switching of the nearest-neighbor spin and orbital correlations and large change in the orbital occupation occur at the M-I transitions. Observation of the change in the orbital occupation at the M-I transitions by the linear dichroic V or Ti 2p x-ray absorption spectroscopy can be a crucial check to this theory.

Journal

  • Journal of the Physical Society of Japan

    Journal of the Physical Society of Japan 73(1), 152-162, 2004-01-15

    The Physical Society of Japan (JPS)

References:  38

Codes

  • NII Article ID (NAID)
    110001954706
  • NII NACSIS-CAT ID (NCID)
    AA00704814
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    00319015
  • NDL Article ID
    6817684
  • NDL Source Classification
    ZM35(科学技術--物理学)
  • NDL Call No.
    Z53-A404
  • Data Source
    CJP  NDL  NII-ELS 
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