title: Pairing symmetry in a two-orbital exchange coupling model of oxypnictides.
abstract: We study the pairing symmetry of a two-orbital J1-J2 model for FeAs layers in oxypnictides. We show that the mixture of an intraorbital unconventional s_{x;{2}y;{2}} approximately cos(k_{x})cos(k_{y}) pairing symmetry, which changes sign between the electron and hole Fermi surfaces, and a very small d_{x;{2}-y;{2}} approximately cos(k_{x})-cos(k_{y}) component is favored in a large part of the J1-J2 phase diagram. A pure s_{x;{2}y;{2}} pairing state is favored for J2>J1. The signs of the d_{x;{2}-y;{2}} order parameters in the two different orbitals are opposite. While a small d_{xy} approximately sin(k_{x})sin(k_{y}) interorbital pairing coexists in the above phases, the intraorbital d_{xy} pairing is not favored even for large J2.
authors.affiliation: Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Kangjun
authors.initials: K
authors.lastname: Seo
authors.forename: B Andrei
authors.initials: BA
authors.lastname: Bernevig
authors.forename: Jiangping
authors.initials: J
authors.lastname: Hu