Two types of s-wave pairing due to magnetic and orbital fluctuations in the two-dimensional 16-band d-p model for iron-based superconductors

We study superconductivity in the two-dimensional 16-band d-p model extracted from a tight-binding fit to the band structure of LaFeAsO, using the random phase approximation. When the intraorbital repulsion U is larger than the interorbital one U^′, an extended s -wave (s± -wave) pairing with sign reversal of order parameter is mediated by antiferromagnetic spin fluctuations, while when U< U^′ another kind of s -wave (s++ -wave) pairing without sign reversal is mediated by ferro-orbital fluctuations. The s++ -wave pairing is enhanced due to the electron-phonon coupling and then can be expanded over the realistic parameter region with U> U^′.