Resonant Raman scattering in thePb2Sr2(Y,Ca)Cu3O8+δsuperconductor

Abstract

We have measured resonant phonon Raman profiles of a superconducting ${\mathrm{Pb}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{Y}}_{0.75}$ ${\mathrm{Ca}}_{0.25}$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{8+\mathrm{\delta }}$ crystal for laser energies from 1.65 to 2.7 eV. The resonances at 1.75 and 2.55 eV and the rise towards the uv, also seen in ellipsometry, are assigned to transitions involving the &–O(3) $p_x$,y, and Pb-O(1) complexes. There exists a relationship between the phonon-induced atomic motions and the location in the unit cell of the electronic transition. We also assign additional peaks that appear under resonant conditions.