INVESTIGATION OF THE TEMPERATURE-DEPENDENCE OF ELECTRON AND PHONON RAMAN-SCATTERING IN SINGLE-CRYSTAL YBA2CU3O6.952

Detailed Raman-scattering measurements have been performed on high-quality YBa2Cu3O6.952 single crystal (T(c)=93K, DELTAT(c)=0.3 K). A sharp (FWHM 7.2 cm at 70 K and 10.0 cm-1 at 110 K) 340 cm-1 phonon mode has been observed in B1g polarization. An electronic scattering peak at 500 cm-1 in the B1g polarization extends down to 250 cm-1. These FWHM values determine the upper limit of the homogeneous linewidth of the phonon and electronic excitations. The start of the electronic spectral function renormalization and of the 340 cm-1 mode anomalies (frequency softening, linewidth sharpening, and intensity increase) have been observed to occur approximately 40 K above T(c). The 340 cm-1 mode Fano shape analysis has been performed and the temperature dependences of the Fano shape parameters have been estimated. All 340 cm-1 mode anomalies have been explained by the electronic spectral function renormalization.