Evidence for Suppressed Screening on the Surface of High Temperature La2−xSrxCuO4 and Nd2−xCexCuO4 Superconductors
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
DOI 10.1103/PhysRevLett.95.177002 · Physical Review Letters
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Abstract
Hard x-ray photoemission spectroscopy (PES) of Cu core electronic states, with a probing depth of ∼60 Å, is used to show that the Zhang-Rice singlet feature is present in La2CuO4 but is absent in Nd2CuO4. Hole and electron doping in La2−xSrxCuO4 (LSCO) and Nd2−xCexCuO4 (NCCO) result in new well-screened features which are missing in soft x-ray PES. Impurity Anderson model calculations establish screening from doped states as its origin, which is strongly suppressed within 15 Å of the surface. Complemented with x-ray absorption spectroscopy, the small chemical-potential shift in core levels (∼0.2 eV) are shown to be consistent with modifications of valence and conduction band states spanning the band gap (∼1 eV) upon hole and electron doping in LSCO and NCCO.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Nd1.85Ce0.15CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 22 | Pressure not reported | unknown |
| La1.85Sr0.15CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 36 | Pressure not reported | unknown |
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