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Evidence for suppressed metallicity on the surface of La2-xSrxCuO4 and Nd2-xCexCuO4

M. Taguchi·A. Chainani·K. Horiba·Y. Takata·M. Yabashi·K. Tamasaku·Y. Nishino·D. Miwa·T. Ishikawa·T. Takeuchi·K. Yamamoto·M. Matsunami·S. Shin·T. Yokoya·E. Ikenaga·K. Kobayashi·T. Mochiku·K. Hirata·J. Hori·K. Ishii·F. Nakamura·T. Suzuki
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Abstract

Hard X-ray Photoemission spectroscopy (PES) of copper core electronic states, with a probing depth of $\sim$60 Å, is used to show that the Zhang-Rice singlet feature is present in La$_2$CuO$_4$ but is absent in Nd$_2$CuO$_4$. Hole- and electron doping in La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) and Nd$_{2-x}$Ce$_x$CuO$_4$ (NCCO) result in new well-screened features which are missing in soft X-ray PES. Impurity Anderson model calculations establish metallic screening as its origin, which is strongly suppressed within 15 $\textÅ$ of the surface. Complemented with X-ray absorption spectroscopy, the small chemical-potential shift in core levels ($\sim0.2$ eV) are shown to be consistent with modifications of valence and conduction band states spanning the band gap ($\sim1$ eV) upon hole- and electron-doping in LSCO and NCCO.

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M. Taguchi, A. Chainani, K. Horiba, Y. Takata, M. Yabashi, K. Tamasaku, Y. Nishino, D. Miwa, T. Ishikawa, T. Takeuchi, K. Yamamoto, M. Matsunami, S. Shin, T. Yokoya, E. Ikenaga, K. Kobayashi, T. Mochiku, K. Hirata, J. Hori, K. Ishii, F. Nakamura, T. Suzuki. 2005-01-26. Evidence for suppressed metallicity on the surface of La2-xSrxCuO4 and Nd2-xCexCuO4. https://doi.org/10.1103/physrevlett.95.177002

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