NODES OF THE SUPERCONDUCTING GAP PROBED BY ELECTRONIC RAMAN-SCATTERING IN HGBA2CACU2O6-CRYSTALS(DELTA SINGLE)

Pure electronic Raman spectra with no phonon structures superimposed t o the electronic continuum are reported, in optimally doped HgBa2CaCu2 O6+delta single crystals (T-c = 126 K). As a consequence, the spectra in the A(1g), B-1g and B-2g symmetries, including the crucial low-ener gy frequency dependence of the electronic scattering, are directly and reliably measured. The B-2g and, most strikingly, the B-1g spectra ex hibit a strong intrinsic linear term, which suggests that the nodes ar e shifted from the [110] and [110] directions, a result inconsistent w ith a pure d(x2-y2) model.