ELECTRONIC RAMAN-SCATTERING OF SUPERCONDUCTING YBA2CU3OY SINGLE-CRYSTALS

The A1g and B1g low-energy Raman continua of YBa2Cu3Oy (Y123) single c rystals, with y = 7.0, 6.99, and 6.93, have been investigated. It is f ound that the peak frequency of the A1g continuum is equal to 310 +/- 10 cm-1 and independent of oxygen concentration for y in the above ran ge. The central frequency of the broad peak in the B1g continuum, howe ver, shifts from about 470 cm-1 for y approximately 7.0 to 550 cm-1 fo r y approximately 6.93. Thus, a relatively small change in oxygen conc entration results in a significant redistribution of the states contri buting to the B1g continuum. Assuming the low-energy portions of the c ontinua are electronic in origin, the Raman spectra have been calculat ed and the results compared to the experimental spectra. It is suggest ed that the Raman continua arise, at least in part, from scattering ac ross a spin fluctuation-induced pseudogap.