PHONON RAMAN-SPECTROSCOPY OF SUPERCONDUCTING BI2SR2CACU2O8+DELTA SINGLE-CRYSTALS

We report unpolarized and polarized Raman spectra on the ab- and bc-planes of a Bi2Sr2CaCu2O8+δ single crystal. While most phonons have Ag- symmetry, one mode with B1g-symmetry is detected at 275 cm-1. For the phonons at 463 cm-1 and 650 cm-1, the temperature dependence of the frequency and the linewidth is measured in the temperature range from 5 K up to room temperature. We find a softening of the frequency of the 463-cm-1 (T = 295 K) mode below Tc and assign this mode to the out-of-plane in-phase vibration of the oxygen in the CuO2-layers. © 1990.