title: Four-unit-cell superstructure in the optimally doped YBa2Cu3O6.92 superconductor.
abstract: Diffuse x-ray scattering measurements reveal that the optimally doped YBa2Cu3O6.92 superconductor is intrinsically modulated due to the formation of a kinetically limited 4-unit-cell superlattice, q(0)=(1/4, 0, 0), along the shorter Cu-Cu bonds. The superlattice consists of large anisotropic displacements of Cu, Ba, and O atoms, respectively, which are correlated over approximately 3-6 unit cells in the ab plane, and appears to be consistent with the presence of an O-ordered "ortho-IV" phase. Long-range strains emanating from these modulated regions generate an inhomogeneous lattice which may play a fundamentally important role in the electronic properties of yttrium-barium-copper-oxides.
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA. zahir@aps.anl.gov
authors.forename: Zahirul
authors.initials: Z
authors.lastname: Islam
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authors.lastname: Liu
authors.forename: S K
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authors.lastname: Sinha
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authors.lastname: Lang
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authors.lastname: Moss
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authors.lastname: Srajer
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authors.lastname: Wochner
authors.forename: D R
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authors.lastname: Lee
authors.forename: D R
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authors.lastname: Haeffner
authors.forename: U
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authors.lastname: Welp