Atomic-layer-resolved composition and electronic structure of the cuprate Bi2Sr2CaCu2O8+δ from soft x-ray standing-wave photoemission
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Atomic-layer-resolved composition and electronic structure of the cuprate Bi2Sr2CaCu2O8+δ from soft x-ray standing-wave photoemission

  • Author(s): Kuo, Cheng-Tai
  • Lin, Shih-Chieh
  • Conti, Giuseppina
  • Pi, Shu-Ting
  • Moreschini, Luca
  • Bostwick, Aaron
  • Meyer-Ilse, Julia
  • Gullikson, Eric
  • Kortright, Jeffrey B
  • Nemšák, Slavomír
  • Rault, Julien E
  • Le Fèvre, Patrick
  • Bertran, François
  • Santander-Syro, Andrés F
  • Vartanyants, Ivan A
  • Pickett, Warren E
  • Saint-Martin, Romuald
  • Taleb-Ibrahimi, Amina
  • Fadley, Charles S
  • et al.
Abstract

© 2018 American Physical Society. A major remaining challenge in the superconducting cuprates is the unambiguous differentiation of the composition and electronic structure of the CuO2 layers and those of the intermediate layers. The large c axis for these materials permits employing soft x-ray (930.3 eV) standing wave (SW) excitation in photoemission that yields atomic layer-by-layer depth resolution of these properties. Applying SW photoemission to Bi2Sr2CaCu2O8+δ yields the depth distribution of atomic composition and the layer-resolved densities of states. We detect significant Ca presence in the SrO layers and oxygen bonding to three different cations. The layer-resolved valence electronic structure is found to be strongly influenced by the atomic supermodulation structure, as determined by comparison to density functional theory calculations, by Ca-Sr intermixing, and by correlation effects associated with the Cu 3d-3d Coulomb interaction, further clarifying the complex interactions in this prototypical cuprate. Measurements of this type for other quasi-two-dimensional materials with large c represent a promising future direction.

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