Dynamic charge inhomogeneity in cuprate superconductors.

The inelastic x-ray scattering spectrum for phonons of Δ(1) symmetry, including the CuO bond-stretching phonon dispersion, is analyzed by means of Lorentz fitting for HgBa(2)CuO(4) and Bi(2)Sr(2)CuO(6), using recently calculated phonon frequencies as input parameters. The resulting mode frequencies of the fit are almost all in good agreement with the calculated data. An exception is the case for the second-highest Δ(1) branch compromising the bond-stretching modes, which disagrees for both compounds with the calculations. This branch shows an anomalous softening with a minimum around the wavevector [Formula: see text], at variance with the calculation predictions. Such a disparity with the calculated results, that are based on the assumption of an undisturbed translation and point group invariant electronic structure of the CuO plane, indicates some static charge inhomogeneities in the measured probes. Most likely these will be charge stripes along the CuO bonds which have the strongest coupling to certain longitudinal bond-stretching modes, that in turn self-consistently induce corresponding dynamic charge inhomogeneities. The symmetry breaking by the mix of dynamic and static charge inhomogeneities can lead to a reconstruction of the Fermi surface into small pockets.