Phenomenological approach to the superconducting gap of Bi2Sr2CaCu2O8+δ

A self-consistent gap equation is modified for purely two-dimensional dx2-y2 symmetry singlet Cooper-pairs, and numerically solved by introducing a phenomenological pair interaction potential. It is found that the calculations including the pair interaction potential well reproduce the temperature dependence of the normalized superconducting gap of Bi2Sr2CaCu2O8+δ and showed that the present calculations are consistent with the condition of the free energy minimum. It is pointed out that the attractive pair interaction potential introduced here may be related to the spin-exchange interaction on a spin singlet state.