Europhys. Lett.
Volume 68, Number 4, November 2004
Page(s) 557 - 563
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 27 October 2004
Europhys. Lett., 68 (4), pp. 557-563 (2004)
DOI: 10.1209/epl/i2004-10240-4

Hard X-ray core-level photoemission of $\chem{V_2O_3}$

N. 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 $\chem{V_2O_3}$ using hard X-ray ( $\tx{HX}:h\nu=5940$ $\un{eV}$) core-level photoemission spectroscopy (PES). HX-PES enables a bulk probe of the electronic structure in the paramagnetic metallic and antiferromagnetic insulating phases. Metallic $\chem{V_2O_3}$ 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 ( $\tx{SX}:h\nu=1450$ $\un{eV}$), 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