Hard X-ray Structural Studies of HgBa$_2$CuO$_{4+\delta}$

Recent high-energy x-ray diffuse scattering work on the compounds YBCO and BSCCO shows that these high-$T_c$ superconductors are typically intrinsically inhomogeneous [1-3]. These inhomogeneities are short-range-ordered lattice modulations driven by oxygen dopants, and they appear to have an important role in the electronic, transport, and spectroscopic properties of these systems. HgBa$_2$CuO$_{4+\delta}$ (Hg1201) has a simple structure and the highest $T_c$ (at optimal doping) among all single-layer compounds. It is thus a perfect candidate system to address the issue of charge modulations. Here we present evidence for short-range incommensurate displacement modulations and discus our results in the context of similar findings in other compounds. \begin{enumerate} \item Z. Islam et al. PRL 93, 157008 (2004) \item J. Strempfer et al. PRL 93, 157007 (2004) \item J. P. Castellan et al. http://arXiv.org/abs/cond-mat/0507505 \end{enumerate}