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Physical review / B 98(15), 155133 (2018). doi:10.1103/PhysRevB.98.155133, A major remaining challenge in the superconducting cuprates is the unambiguous differentiation of thecomposition and electronic structure of the CuO$_2$ layers and those of the intermediate layers. The large caxis for these materials permits employing soft x-ray (930.3 eV) standing wave (SW) excitation in photoemissionthat yields atomic layer-by-layer depth resolution of these properties. Applying SW photoemissionto $\mathrm{Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}}$ yields the depth distribution of atomic composition and the layer-resolved densities ofstates. We detect significant Ca presence in the SrO layers and oxygen bonding to three different cations. Thelayer-resolved valence electronic structure is found to be strongly influenced by the atomic supermodulationstructure, as determined by comparison to density functional theory calculations, by Ca-Sr intermixing, and bycorrelation effects associated with the Cu 3d-3d Coulomb interaction, further clarifying the complex interactionsin this prototypical cuprate. Measurements of this type for other quasi-two-dimensional materials with large crepresent a promising future direction., Published by APS, Woodbury, NY