Pairing Symmetry in a Two-Orbital Exchange Coupling Model of Oxypnictides

Understand

We study the pairing symmetry of a two orbital $J_1-J_2$ model for FeAs layers in oxypnictides.

• We vary the doping and the value of $J_1$ and $J_2$ to compare all possible pairing symmetries in a mean-field calculation.
• We show that the mixture of an intra-orbital unconventional $s_{x^2y^2}\sim \cos(k_x)\cos(k_y)$ pairing symmetry and a $d_{x^2-y^2}\sim \cos(k_x)-\cos(k_y)$ pairing symmetry is favored in a large part of $J_1-J_2$ phase diagram.
• A pure $ s_{x^2y^2}$ pairing state is favored for $J_2>>J_1$.