INELASTIC LIGHT-SCATTERING AT HIGH-ENERGY EXCITATIONS IN DOPED CUPRATE SUPERCONDUCTORS

We present Raman spectra of low-and high-energy spin and charge excita tions from Y1-xPrxBa2Cu3O7 and YBa2Cu3O6+x thin films as well as from Y1-xPrxBa2Cu3O7 single crystals. We show that a rearrangement of spect ral weight in B-1g and A(1g) symmetry occurs below there respective cr itical temperatures T-c of the samples at energies of about 5-6 times 2 Delta, where Delta is the magnitude of the superconducting order par ameter. The redistribution of spectral weight shifts with doping towar ds lower energies. For optimally doped samples strong renormalization effects of the electronic and phononic structures occur. We discuss ou r results in terms of a simplified t-J model having magnetic and charg e like scattering channels. As far as the magnetic response is concern ed, we apply the Heisenberg model of antiferromagnetism including self -energy contributions to the one-magnon states. This shows that the re arrangement at least partly results from an interaction between the re maining antiferromagnetism and the superconductivity. Moreover, the ch argelike response at high energies seems to be influenced by the super conducting transition as well,indicating a strong interplay between ho les and magnons in the normal and superconducting state.