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Photoemission evidence for a Mott-Hubbard metal-insulator transition in VO$_2$

R. Eguchi·M. Taguchi·M. Matsunami·K. Horiba·K. Yamamoto·Y. Ishida·A. Chainani·Y. Takata·M. Yabashi·D. Miwa·Y. Nishino·K. Tamasaku·T. Ishikawa·Y. Senba·H. Ohashi·Y. Muraoka·Z. Hiroi·S. Shin
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Abstract

The temperature ($T$) dependent metal-insulator transition (MIT) in VO$_2$ is investigated using bulk sensitive hard x-ray ($\sim$ 8 keV) valence band, core level, and V 2$p-3d$ resonant photoemission spectroscopy (PES). The valence band and core level spectra are compared with full-multiplet cluster model calculations including a coherent screening channel. Across the MIT, V 3$d$ spectral weight transfer from the coherent ($d^1\underbar{\it {C}}$ final) states at Fermi level to the incoherent ($d^{0}+d^1\underbar{\it {L}}$ final) states, corresponding to the lower Hubbard band, lead to gap-formation. The spectral shape changes in V 1$s$ and V 2$p$ core levels as well as the valence band are nicely reproduced from a cluster model calculations, providing electronic structure parameters. Resonant-PES finds that the $d^1\underbar{\it{L}}$ states resonate across the V 2$p-3d$ threshold in addition to the $d^{0}$ and $d^1\underbar{\it {C}}$ states. The results support a Mott-Hubbard transition picture for the first order MIT in VO$_2$.

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R. Eguchi, M. Taguchi, M. Matsunami, K. Horiba, K. Yamamoto, Y. Ishida, A. Chainani, Y. Takata, M. Yabashi, D. Miwa, Y. Nishino, K. Tamasaku, T. Ishikawa, Y. Senba, H. Ohashi, Y. Muraoka, Z. Hiroi, S. Shin. 2008-07-30. Photoemission evidence for a Mott-Hubbard metal-insulator transition in VO$_2$. https://doi.org/10.1103/physrevb.78.075115

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