Identification of the Bulk Pairing Symmetry in High-Temperature Superconductors: Evidence for an Extended s wave 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 that 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 ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+y}$ and ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}y}.$