In-gap state and effect of light illumination inCuIr2S4probed by photoemission spectroscopy

2008/08/13 by Kou Takubo, K. Takubo, T. Mizokawa +4 · 17 citations
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Analytical Chemistry (journal) #Chemistry #Condensed matter physics #Fermi level #Magnetic and transport properties of perovskites and related materials #Materials science #Physics #Physics of Superconductivity and Magnetism #cond-mat.str-el

paper · pdf · doi:10.1103/physrevb.78.245117

published in Physical Review B 78(24), 245117-1-245117-7 (American Physical Society) · 14 pages, 5 figures

arxiv created 2008/08/13 · openalex publication_date 2008/12/19 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

We have studied disorder-induced in-gap states and effect of light illumination in the insulating phase of spinel-type CuIr₂S₄ using ultraviolet photoemission spectroscopy (UPS). The Ir³⁺/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 (E_F), corresponding to the variable range hopping transport observed in resistivity. The spectral weight at E_F 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⁺-Ir⁴⁺ bipolaronic hopping and disorder effects are responsible for the conductivity of CuIr₂S₄.

Citations

• Variation of the metal-insulator transition and formation of bipolarons by Cd doping in the thiospinel systemCu1−xCdxIr2S4
• X-ray-induced disordering of the dimerization pattern and apparent low-temperature enhancement of lattice symmetry in spinelCuIr2S4
• Coulomb gap and low temperature conductivity of disordered systems