Nodes of the superconducting gap probed by electronic Raman scattering in HgBa2CaCu2O6 + δ single crystals

Pure electronic Raman spectra with no phonon structures superimposed to the electronic continuum are reported, in optimally doped HgBa2CaCu2O6 + δ single crystals (Tc = 126 K). As a consequence, the spectra in the A1g, B1g and B2g symmetries, including the crucial low-energy frequency dependence of the electronic scattering, are directly and reliably measured. The B2g and, most strikingly, the B1g spectra exhibit a strong intrinsic linear term, which suggests that the nodes are shifted from the [110] and [ 11̄0] directions, a result inconsistent with a pure dx2 − y2 model.