Raman-study of photoinduced chain-oxygen ordering in RBa2Cu3O7-δ

We investigated Raman-forbidden signals in RBa₂Cu₃O_7-δ with R = Y or Pr, which lose intensity under illumination at low temperatures. These defect-induced peaks are only visible in oxygen-deficient material and for light polarized parallel to the copper-oxygen chains along the material´s b-axis. In a first, two-laser based experiment we established that the bleaching effect of the light is polarization dependent as well. From this and other known properties we conclude that the signal is connected to the copper-oxygen chains, reflecting their state of disorder, and is thus closely related to aging and to the persistent photoconductivity effect in the material. In a second set of experiments we followed the temperature dependence of the Raman spectra and the intensity decrease.