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arXiv · 1504.03798

Electronic structure of Mott-insulator CaCu3Ti4O12: Photoemission and inverse photoemission study

H. J. Im·M. Iwataki·S. Yamazaki·T. Usui·S. Adachi·M. Tsunekawa·T. Watanabe·K. Takegahara·S. Kimura·M. Matsunami·H. Sato·H. Namatame·M. Taniguchi
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Abstract

We have performed the photoemission and inverse photoemission experiments to elucidate the origin of Mott insulating states in A-site ordered perovskite CaCu$_3$Ti$_4$O$_{12}$ (CCTO). Experimental results have revealed that Cu 3$d$-O 2$p$ hybridized bands, which are located around the Fermi level in the prediction of the local-density approximation (LDA) band calculations, are actually separated into the upper Hubbard band at $\sim$ 1.5 eV and the lower Hubbard band at $\sim$ $-$1.7 eV with a band gap of $\sim$ 1.5-1.8 eV. We also observed that Cu 3$d$ peak at $\sim$ $-$3.8 eV and Ti 3$d$ peak at $\sim$ 3.8 eV are further away from each other than as indicated in the LDA calculations. In addition, it is found that the multiplet strucutre around $-$9 eV includes a considerable number of O 2$p$ states. These observations indicate that the Cu 3$d$ and Ti 3$d$ electrons hybridized with the O 2$p$ states are strongly correlated, which originates in the Mott-insulating states of CCTO.

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H. J. Im, M. Iwataki, S. Yamazaki, T. Usui, S. Adachi, M. Tsunekawa, T. Watanabe, K. Takegahara, S. Kimura, M. Matsunami, H. Sato, H. Namatame, M. Taniguchi. 2015-05-17. Electronic structure of Mott-insulator CaCu3Ti4O12: Photoemission and inverse photoemission study. https://doi.org/10.1016/j.ssc.2015.05.007

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