Synchrotron X-ray study reveals oxygen chains in HgBa$_{2}$CuO$_{4+\delta }$

X-ray scattering work shows that the double-layer high-$T_{c}$ superconductors YBa$_{2}$Cu$_{3}$O$_{8+d }$and Bi2Sr$_{2}$CaCu$_{2}$O$_{6+\delta }$ are intrinsically inhomogeneous [1-3], with short-range lattice modulations driven by oxygen dopants. HgBa$_{2}$CuO$_{4+\delta }$(Hg1201) has a simpler (tetragonal) structure and the highest $T_{c}$ (at optimal doping) among all single-layer cuprates. It is thus a very good candidate system to address the issue of charge modulations. Using synchrotron X-ray scattering and high-quality single crystals, we have observed a short-range lattice modulations in Hg1201. Careful analysis of the diffuse intensity pattern, and a study of the doping and temperature dependence, point toward the formation of local one-dimensional order in the form of uncorrelated oxygen chains in the charge-reservoir layer. The chains exist at intermediate and high doping, form along [100], and have typical lengths of 15-30 lattice constants [4]. \begin{enumerate} \item Z. Islam \textit{et al}. PRL \textbf{93} 157008 (2004) \item J. Strempfer \textit{et al}. PRL \textbf{93}, 157007 (2004) \item J. P. Castellan \textit{et al}. PRB \textbf{73}, 174505 (2006) \item G. Chabot-Couture, W. Tabis, J. N. Hancock Z. Islam, L. Lu, G. Yu, Y. Li, X. Zhao, Y. Ren, A. Mehta, M. Greven, (unpublished) \end{enumerate}