Identification of the bulk pairing symmetry in high-temperature superconductors: Evidence for an extendedswave with eight line nodes

Abstract

we identify the intrinsic bulk pairing symmetry for both electron and hole-doped cuprates from the existing bulk-and nearly bulk-sensitive experimental results such as magnetic penetration depth, Raman scattering, single-particle tunneling, Andreev reflection, nonlinear Meissner effect, neutron scattering, thermal conductivity, specific heat, and angle-resolved photoemission spectroscopy. These experiments consistently show that the dominant bulk pairing symmetry in hole-doped cuprates is of extended s-wave with eight line nodes, and of anisotropic s-wave in electron-doped cuprates. The proposed pairing symmetries do not contradict some surface-and phase-sensitive experiments which show a predominant d-wave pairing symmetry at the degraded surfaces. We also quantitatively explain the phase-sensitive experiments along the c-axis for both Bi2Sr2CaCu2O8+y and YBa2Cu3O7−y.

Specific heat evidence for bulk s-wave gap symmetry of optimally electron-doped Pr1.85Ce0.15CuO4 −ysuperconductors

“…These tunneling experiments along with independent penetration depth measurements [17] consistently indicate a possible crossover from a d-wave scenario in the deeply underdoped region to a nodeless swave scenario in the higher-doping region, in agreement with the theoretical prediction based on a phonon-mediated pairing mechanism [18]. Very recently, the bulk-sensitive Raman scattering data for Nd 1.85 Ce 0.15 CuO 4−y have been quantitatively explained in terms of an anisotropic s-wave gap with a large minimum gap of about 3 meV [19], in quantitative agreement with the earlier penetration depth data [1,7]. Further, the bulk-and phase-sensitive data for the nonmagnetic pair-breaking effect (T c is nearly independent of the residual resistivity) in optimally doped cuprates unambiguously rule out any d-wave gap symmetry [19].…”

How does the break-junction quasiparticle tunnel conductance look like for d-wave superconductors?

“…Finally, we attract attention to the insensitivity of the quasiparticle tunnel current to the phase of the anisotropic order parameter. Therefore, contrary to the case of the Josephson current [28,31,[79][80][81][87][88][89][90][91], our results completely coincide with those for the so-called extended swave superconducting order parameter [92][93][94][95][96][97] proportional to cos 2θ in the k space.…”

Nearly isotropics-wave gap in the bulk of the optimally electron-doped superconductorNd1.85Ce0.15Zhao1 2010Phys. Rev. BSelf Cite172120View full textAdd to dashboardCite

“…Other bulksensitive experiments on hole-doped cuprates 5,6 can be quantitatively explained by extended s-wave gap. 7 In contrast, the issue as to whether there exist line nodes in the gap function of electron-doped ͑n-type͒ cuprates remains controversial. Phase and surface-sensitive experiments 8 provided evidence for pure d-wave order-parameter ͑OP͒ symmetry in optimally doped and overdoped n-type cuprates.…”