In-gap state and effect of light illumination in CuIr2S 4 probed by photoemission spectroscopy

K. Takubo, Takashi Mizokawa, N. Matsumoto, S. Nagata

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Abstract

We have studied disorder-induced in-gap states and effect of light illumination in the insulating phase of spinel-type CuIr2S 4 using ultraviolet photoemission spectroscopy (UPS). The Ir 3+/Ir4+ charge-ordered gap appears below the metal-insulator transition temperature. However, in the insulating phase, in-gap spectral features with softgap are observed in UPS just below the Fermi level (EF), corresponding to the variable range hopping transport observed in resistivity. The spectral weight at EF is not increased by light illumination, indicating that the Ir4+-Ir4+ dimer is very robust, although the long-range octamer order would be destructed by the photoexcitation. Present results suggest that the Ir4+-Ir 4+ bipolaronic hopping and disorder effects are responsible for the conductivity of CuIr2S4.

Original languageEnglish
Article number245117
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume78
Issue number24
DOIs
Publication statusPublished - 2008 Dec 1
Externally publishedYes

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ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

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