Four-unit-cell superstructure in the optimally doped YBa2Cu3O6.92 superconductor.

Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
Physical Review Letters (Impact Factor: 7.73). 11/2004; 93(15):157008. DOI: 10.1103/PhysRevLett.93.157008
Source: PubMed

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.

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