We study theoretically the symmetry of pairing when charge and spin fluctuations coexist to mediate the pairing for the extended Hubbard model on the square lattice, where the off-site repulsion V controls the charge fluctuation. Phase diagram is obtained, with the fluctuation exchange approximation, on the plane of V and the band filling n (quarter to half filling), which reveals: (i) a transition between dxy and dx2-y2 pairing symmetries for a weaker V, (ii) f-pairing in between the dx2-y2 and CDW phases for a stronger V, and (iii) for an anisotropic (quasi-1D) case the pairing symmetry changed, in agreement with a previously proposed "generic phase diagram" (Phys. Rev. B 63 (2001) 094509), as d→f→s with V. All these are consequences of the structure in the charge and spin susceptibilities which have peaks habitating at common or segregated positions, depending on V and n, in k space.
- Extended Hubbard model
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering