Symmetry of the superconducting gap in HgBa2CaCu2O6+δ single crystals from electronic Raman scattering

Pure electronic Raman spectra with no phonon structures superimposed on the low energy electronic continuum, are reported for the first time, in optimally doped HgBa2CaCu2O6+δ single crystals (Tc = 126 K). Our low temperature spectra (15 K) for the A1g, B1g and B2g symmetries exhibit striking differences with previous data in Bi2Sr2CaCu2O8+δ . The shape of the spectra for the various symmetries cannot be fitted by Devereaux’s dx2−y2 calculations, but strongly suggests a dxy gap, with its minima along the [100]