TEMPERATURE-DEPENDENCE OF THE LINEWIDTH OF THE 500 CM-1 RAMAN MODE OF YBA2CU3O7-X

The temperature dependence of the 500 cm-1 Raman active phonon has been carefully investigated in Raman spectra obtained from pressed and sintered pellets of YBa2Cu3O7-x with x ≈ 0. The 500 cm-1 phonon arises from vibrations of the O (4) bridging oxygen atoms which are believed to be situated in a strongly anharmonic potential well. The linewidth of the 500 cm-1 mode has thus been studied as a function of temperature. In several samples the linewidth was observed to decrease by about 3 cm-1 near Tc and to increase again at lower temperature. A linear chain model is used to estimate the effect of charge transfer fluctuations on the 500 cm-1 mode and the results suggest that coupling of such fluctuations to the 500 cm-1 mode may influence the observed behaviour near Tc. © 1990.