Abstract
We have studied the electronic structure of the spinel-type compound using x-ray photoemission spectroscopy (XPS). undergoes a metal-insulator transition (MIT) at . In going from the metallic to insulating states, the valence-band photoemission spectrum shows a gap opening at the Fermi level and a rigid-band shift of . In addition, the Ir core-level spectrum is dramatically changed by the MIT. The Ir line shape of the insulating state can be decomposed into two contributions, consistent with the charge disproportionation of . XPS measurements under laser irradiation indicate that the charge disproportionation of is very robust against photo-excitation in contrast to which shows photo-induced valence transition.
- Received 17 March 2005
DOI:https://doi.org/10.1103/PhysRevLett.95.246401
©2005 American Physical Society