Anisotropies of Raman scattering cross-sections of YBa2Cu3O6+δ compounds

Abstract We present Raman scattering results on superconducting single crystals of YBa 2 Cu 3 O 6+ δ for γ≥0.5 at temperatures below and above the critical temperature. A complete polarization analysis of these crystals allows us to deduce the cross-sections of the Raman active phonon modes in the three crystallographic directions. The electronic Raman scattering of A g symmetry and with the polarization vector in the a-b -plane reveals an energy gap 2Δ of 3.3 to 3.6 k B T c for crystals with δ≥0.8. No clear gap is found in B 1g symmetry or for polarizations parallel to the c -axis.