Light scattering on phonons in YBa2Cu3O7-δ crystals

Qualitative theory of light scattering on 335, 435 and 500 cm-1 phonons in YBa2Cu3O7-δ was constructed. Preliminary ZZ-polarization for 500 cm-1 phonon, related with tridge oxygen, is explained by pronounced difference of overlap integrals of dpσ and dpπ type, where d and p-atomic orbitals of copper and oxygen. It is shown that single phonon light scattering by CuO2-planes is resolved only due to distortions of their form and therefore can't be used for determining force of electron-phonon bond in them. Explanation of high scattering intensity on the planar 435 cm-1 phonon in ZZ-component of the spectrum, based on participation of bridge oxygen in CuO2-plane vibration, is suggested. High intensity of scattering on the planar 335 cm-1 phonon in planar (xx and yy) polarizations, as compared to 435 cm-1 phonon, testifies to fulfilment of /E/>>4t criterion, where E-difference of energies on copper and oxygen with account of electron correlations, t-integral of electron transfer. Possibilities of analyzing energy spectrum of charge carriers according to the dependence of scattering intensity on δ were discussed