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

N. Kamakura; M. Taguchi; A. Chainani; Y. Takata; K. Horiba; K. Yamamoto; K. Tamasaku; Y. Nishino; D. Miwa; E. Ikenaga; M. Awaji; A. Takeuchi; H. Ohashi; Y. Senba; H. Namatame; M. Taniguchi; T. Ishikawa; K. Kobayashi; S. Shin

doi:doi:10.1209/epl/i2004-10240-4

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. Shin^{1, 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

Abstract
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.

PACS
71.30.+h - Metal-insulator transitions and other electronic transitions.
79.60.-i - Photoemission and photoelectron spectra.

© EDP Sciences 2004