Orbital character of states at the Fermi level in La2xSrxCuO4 and R2xCexCuO4 (R=Nd,Sm)

E. Pellegrin, N. Nücker, J. Fink, S. L. Molodtsov, A. Gutiérrez, E. Navas, O. Strebel, Z. Hu, M. Domke, G. Kaindl, S. Uchida, Y. Nakamura, J. Markl, M. Klauda, G. Saemann-Ischenko, A. Krol, J. L. Peng, Z. Y. Li, and R. L. Greene
Phys. Rev. B 47, 3354 – Published 1 February 1993
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Abstract

Polarization-dependent x-ray-absorption spectroscopy on the O 1s and Cu 2p edges using the non-surface-sensitive fluorescence method has been performed on single crystals of La2xSrxCuO4+δ, R2xCexCuO4δ (R=Nd and Sm), and the insulating compound Ca0.86Sr0.14CuO2. The experimental results support the picture of a doped charge-transfer insulator. The symmetry of hole states on O and Cu sites has been determined. These have predominantly in-plane, i.e., O 2px,y and Cu 3dx2-y2 character. In p-type doped cuprates for 0<x<0.15 about 8% of the total number of hole states on O sites have O 2pz character, which probably originates from apical O sites. At higher dopant concentration, this number increases. In the n-type doped system 4–11 % of the O 2p states in the energy range of the upper Hubbard band have O 2pz character. In nearly all the systems investigated in this work the fraction of unoccupied Cu 3d3z2-r2 states with respect to the total number of Cu holes in the upper Hubbard band is 3±3 %. At higher energies a high spectral weight with Cu 3d3z2-r2 character (about 40% of the total amount of unoccupied Cu 3d states in the upper Hubbard band) is observed, which is probably caused by a hybridization with Cu 4s and 4p states. The implication of holes in nonplanar orbitals on high-Tc superconductivity in cuprates is discussed.

  • Received 19 October 1992

DOI:https://doi.org/10.1103/PhysRevB.47.3354

©1993 American Physical Society

Authors & Affiliations

E. Pellegrin, N. Nücker, and J. Fink

  • Kernforschungszentrum Karlsruhe, Institut für Nukleare Festkörperphysik, Postfach 3640, W-7500 Karlsruhe, Germany

S. L. Molodtsov, A. Gutiérrez, E. Navas, O. Strebel, Z. Hu, M. Domke, and G. Kaindl

  • Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, W-1000 Berlin 33, Germany

S. Uchida and Y. Nakamura

  • Department of Applied Physics, University of Tokyo, Bunkyo-Ku, Tokyo 113, Japan

J. Markl, M. Klauda, and G. Saemann-Ischenko

  • Physikalisches Institut der Universität Erlangen, W-8520 Erlangen, Germany

A. Krol

  • Department of Physics, State University of New York (SUNY), Buffalo, New York 14260

J. L. Peng, Z. Y. Li, and R. L. Greene

  • Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742

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Issue

Vol. 47, Iss. 6 — 1 February 1993

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