Pairing Type Symmetry in Cuprate Superconductors

We report a brief overview of a number of results on a type of pairing state symmetry in cuprate HTSC from a current literature. The results of recent high-precision measurements of near-nodal d-type gap functions by a modern laser-based ARPES method or by a c-axis twisted Josephson junction for hole doped Bi-2212 system are presented. Recent experimental evidence in favor of d-type pairing symmetry, with a special nonmonotonic functional form, for electron doped cuprate NdCeCuO is discussed. A new essential result on the identification of \({{d}_{{{{x}^{2}} - {{y}^{2}}}}}\) symmetry of superconducting order parameter for parent high-T_c cuprate structure, electron doped infinite layer SrLaCuO system, by the phase sensitive tests is described. A complex of the data presented indicates a vital role of d-wave pairing symmetry, in the special \({{d}_{{{{x}^{2}} - {{y}^{2}}}}}\) form, for high-temperature conductivity in cuprate systems.