Comparison of charge modulations in La1.875Ba0.125CuO4 and YBa2Cu3O6.6

A charge modulation has recently been reported in (Y,Nd)Ba2Cu3O6+x [G. Ghiringhelli et al., Science 337, 821 (2012)]. Here we report Cu L-3 edge soft x-ray scattering studies comparing the lattice modulation associated with the charge modulation in YBa2Cu3O6.6 with that associated with the well-known charge and spin stripe order in La1.875Ba0.125CuO4. We find that the correlation length in the CuO2 plane is isotropic in both cases, and is 259 +/- 9 angstrom for La1.875Ba0.125CuO4 and 55 +/- 15 angstrom for YBa2Cu3O6.6. Assuming weak interplanar correlations of the charge ordering in both compounds, we conclude that the order parameters of the lattice modulations in La1.875Ba0.125CuO4 and YBa2Cu3O6.6 are of the same order of magnitude.