X-ray diffraction study of lattice modulations in an underdoped YBa2Cu3O6+x superconductor

We report a temperature-dependent increase below ∼220 K of diffuse superlattice peaks corresponding to q0=(∼(2/5),0,0) in an underdoped YBa2Cu3O6+x superconductor (x≅0.63). These peaks reveal strong c-axis correlations involving the CuO2 bilayers, show a nonuniform increase below ∼220 K with a plateau for ∼100-160 K, and appear to saturate in the superconducting phase. We propose that this temperature dependence of the superlattice peaks is a possible manifestation of charge stripes in the CuO2 planes which are coupled to the oxygen-ordered superstructure