By applying an exact unitary transformation to a two-band hamiltonian which also includes the effects due to large pnictogen polarizabilities, we show that an attractive spin-mediated Hubbard term appears in the dxz, dyz nearest-neighbour channel. This pairing mechanism implies a singlet superconducting order parameter in iron pnictides.
@article{arxiv.0912.1811,
title = {Pairing mechanism in Fe pnictide superconductors},
author = {R. Chan and M. Gulacsi and A. Ormeci and A. R. Bishop},
journal= {arXiv preprint arXiv:0912.1811},
year = {2013}
}