Raman study of ordering phenomena in copper-oxygen systems

We summarize results of light-scattering experiments in undercloped La2-xSrxCuO4 (LSCO) and YBa2Cu3O6+x (Y- 123) single crystals. Below a doping-dependent temperature close to the pseudogap cross-over line T*(p) new peaks appear in the low-energy part of the spectra. For low doping, p similar or equal to 0.02 holes per CuO2, the features are observed in B-2g symmetry in both LSCO and Y-123. At p=0. 10 the additional contribution exists only in LSCO and is found at B-1g symmetry. We interpret the low-energy peaks in terms of a charge ordering instability. The 'stripes' are fluctuating with preferential orientation along the diagonals and the principle axes at p similar or equal to 0.02 and p=0.10, respectively. (c) 2006 Elsevier Ltd. All rights reserved.