Quantitative evidence for spin-fluctuation-mediated higher-harmonic d-wave components: Hole- and electron-doped cuprates

Experimental evidence for higher harmonics in the cuprate d-wave gap function cos (2φ) or cos (k_x) -cos (k_y) has been slowly mounting. Here we analyze all of the data that have been generated in this field for both hole-doped and electron-doped cuprates, demonstrating a preponderance of these symmetry-allowed terms. We then show that the simple spin-fluctuation pairing mechanism can reproduce the detailed angular dependence of the gap. We also present an analysis of pseudogap higher-harmonic symmetry based on the picture of the Fermi arcs as being due to lifetime broadening.