Hard X-ray core-level photoemission ofN. Kamakura1, M. Taguchi1, A. Chainani1, Y. Takata1, K. Horiba1, K. Yamamoto1, K. Tamasaku2, Y. Nishino2, D. Miwa2, E. Ikenaga3, M. Awaji3, A. Takeuchi3, H. Ohashi3, Y. Senba3, H. Namatame4, M. Taniguchi4, T. Ishikawa2, K. Kobayashi3 and S. Shin1, 5
1 Soft X-ray Spectroscopy Laboratory, RIKEN/SPring-8 Mikazuki-cho, Sayo-gun, Hyogo 679-5148, Japan
2 Coherent X-ray Optics Laboratory, RIKEN/SPring-8 Mikazuki-cho, Sayo-gun, Hyogo 679-5148, Japan
3 JASRI/SPring-8 - Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
4 HiSOR, Hiroshima University - Higashi-Hiroshima, Hiroshima 739-8526, Japan
5 Institute for Solid State Physics, University of Tokyo Kashiwa, Chiba 277-8581, Japan
received 10 August 2004; accepted in final form 24 September 2004
published online 27 October 2004
We study the Mott-Hubbard metal-insulator transition in single-crystal using hard X-ray ( ) core-level photoemission spectroscopy (PES). HX-PES enables a bulk probe of the electronic structure in the paramagnetic metallic and antiferromagnetic insulating phases. Metallic shows additional features at low binding energy to the main peak of V 1s, 2p, and 3s core levels, which vanish in the insulating phase. The low-binding-energy features in the metallic phase are also observed using soft X-rays ( ), but with a reduced relative intensity compared to the HX-PES spectrum. A model cluster calculation including core hole screening by coherent states at the Fermi level, reproduces the low-binding-energy features in the metallic phase. The O 1s core level also shows spectral changes: the asymmetric line shape in the metallic phase transforms to a symmetric line shape in the insulating phase, consistent with the metal-insulator transition. The results indicate screening by coherent states is more effective in the bulk compared to the surface. HX-PES is, thus, a reliable probe of the electronic-structure changes across the metal-insulator transition in strongly correlated electron systems.
71.30.+h - Metal-insulator transitions and other electronic transitions.
79.60.-i - Photoemission and photoelectron spectra.
© EDP Sciences 2004