crystals*

Understanding the origin of superconductivity is one of the greatest challenges in condensed matter physics. An outstanding question remains as to whether superconductivity is related to nematic electronic or magnetic correlations or to structural disorder. In this respect, superconducting Cuprates exhibit many imperfections at their crystallographic sites in addition to a heavily tunable oxygen vacancy framework supporting many short-range oxygen ordering schemes. In this talk, I will discuss the structural properties of five ErBa₂Cu₃O_6+x single crystals with oxygen contents tuned to produce T_C’s = 0, 22, 55, 75 and 92 K. Systematic three-dimensional reciprocal space mapping was performed at sector 6 at the Advanced Photon Source at temperatures between 30 and 300 K. We observe modulated diffuse scattering intensities arising from short-range local correlations between the Ba and Cu layers. The modulated intensities weaken upon increased doping until they disappear for the 92 K crystal. Our data provide no evidence for charge density waves which, if present, must be much weaker than those commonly observed in YBCO, LSCO or other related Cuprates.