PLANE OXYGEN VIBRATIONS AND THEIR TEMPERATURE-DEPENDENCE IN HGBA2CA2CU3O8-CRYSTALS(DELTA SINGLE)

A polarized Raman-scattering investigation of HgBa2Ca2Cu3O8+delta sing le crystals has been performed. The following Raman-active modes assoc iated with oxygen vibrations in the CuO2 planes have been clearly iden tified: the B-1g mode at 245 cm(-1), corresponding to the out-of-phase vibration of the plane oxygens, and the A(1g) mode at 265 cm(-1), cor responding to their in-phase vibration. Another defect-induced A(1g) m ode was also detected at 400 cm(-1). Measurements of the temperature d ependence of these Raman features demonstrate that the A(1g) 265- and 400-cm(-1) modes show abrupt changes in frequency and linewidth across T-c, accompanied by an appreciable intensity enhancement in the super conducting state. However, similar ''anomalies'' were not observed for the 245-cm(-1) phonon of B-1g symmetry.