We have studied the charge-orbital states in spinel- type CuIr 2S 4 and perovskite-type Pr 0.55(Ca 1-y Sr y ) 0.45MnO 3 (PCSMO, y=0.25, 0.40) using X-ray photoemission spectroscopy (XPS) combined with laser illumination. The XPS data of CuIr 2S 4 are dramatically changed by the insulator-metal transition (IMT). The line shape of CuIr 2S 4 in the insulating phase is consistent with the charge disproportionation of Ir 3+:Ir 4+=1:1. Interestingly, a visible light irradiation at low temperature gives a resistance reduction but does not give any spectral change. In case of PCSMO, the IMT is also clearly observed on the XPS data and the peculiar temperature dependence for y=0.25 suggests the coexisting of the ferromagnetic metallic phase and the charge-orbital ordered insulating phase. The spectra after visible light illumination show the enhancement of the density of states at the Fermi level, accompanied with the drop of the resistance.
- Phase competition
- Photo-induced phase transition
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics