Phase diagram of the pairing symmetry in two-dimensional strong-coupling superconductors
Abstract Two-dimensional Eliashberg equations have been solved by use of a mixed interaction with s - and d -channels. It is discussed what kind of pairing symmetry of the superconducting state can be realized when the channel mixing parameters and the band-filling are varied. By changing the mixing parameters and varying the chemical potential μ between zero- and half-filling, the pairing symmetry is determined and summarized into a phase diagram of the symmetry. It is revealed that there is an effective threshold in μ for the appearance of the d -wave superconductivity regardless of the strength of the d -channel interaction. It is also shown that, although the s -wave superconductivity can occur for any value of μ if the s -channel interaction is mixed sufficiently, the d -wave superconductivity has the advantage of achieving a high- T c over the s -wave one, once it occurs.