Phonon Raman scattering from slightly overdoped Bi2Sr2CaCu2O8+d (Bi2212) samples have been investigated under hydrostatic pressure up to 7.2 GPa. The mode-specific Gruneisen parameters scale inversely with the corresponding phonon frequencies, the behavior of which is reminiscent of phonon pressure dependences in molecular solids. We also find that the 140 cm-1 Cu mode exhibits a pronounced nonlinear pressure dependence which correlates to the dependence of Tc versus pressure. The data are interpreted in terms of a non-uniform structural compressibility that results in a redistribution of charge carriers within the Bi2212 unit-cell.
ASJC Scopus subject areas
- Condensed Matter Physics