Electronic Raman scattering in HgBa2Ca2Cu3O8+delta single crystals: Analysis of the superconducting state

[摘要] Electronic Raman-scattering measurements have been performed on HgBa2Ca2Cu3O8+delta single crystals in the superconducting state. Pure electronic Raman spectra with no phonon structures hindering the analysis of the electronic continuum have been obtained. As a consequence, the spectra in the pure B-1g and B-2g symmetries are directly and reliably analyzed and the pure A(1g) contribution can be easily identified. Below the critical temperature T-C, two electronic structures at 2 Delta similar to 6.4 k(B)T(c) and 2 Delta similar to 9.4 k(B)T(c) are clearly seen. Both are observed simultaneously in pure A(1g) symmetry, the highest energy one being located at the energy of the B-1g maximum. These two maxima disappear at T-C and do not soften significantly as the temperature is raised up to T-C. The low-energy frequency dependence of the B-1g electronic response is strongly linear, for various excitation lines in the 476.5-547.1 nm range. Such experimental data cannot be reconciled with a pure d(x1-y2) symmetry. Instead, they strongly advocate in favor of an anisotropic superconducting gap with two distinct gap maxima and of nodes existing outside the [110] and [1,(1) over bar,0] directions in k space. We discuss in detail the simplest order parameter compatible with our experimental findings. [S0163-1829(98)00238-0].

[关键词] UNCONVENTIONAL SUPERCONDUCTORS;HIGH-T(C) SUPERCONDUCTORS;TEMPERATURE-DEPENDENCE;OXYGEN STOICHIOMETRY;LIGHT-SCATTERING;GAP EXCITATIONS;D-WAVE;YBA2CU3O7-DELTA;TL2BA2CUO6+DELTA;BI2SR2CACU2O8