Superconductivity in multi-orbital t-J1-J2 model and its implications for iron pnictides

Motivated by the bad metal behavior of the iron pnictides, we study a multi-orbital t-J(1)-J(2) model and investigate possible singlet superconducting pairings. Magnetic frustration by itself leads to a large degeneracy in the pairing states. The kinetic energy breaks this into a quasi-degeneracy among a reduced set of pairing states. For small electron and hole Fermi pockets, an A(1g) state dominates over the phase diagram but a B-1g state has close-by energy. In addition to the nodeless A(1g) s(x2y2) channel, the nodal A(1g) s(x2+y2) and B-1g d(x2-y2) channels are also competitive in the magnetically frustrated J1 similar to J2 parameter regime. An A(1g) vertical bar iB(1g) state, which breaks time-reversal symmetry, occurs at low temperatures in part of the phase diagram. Implications for the experiments in the iron pnictides are discussed. Copyright (c) EPLA, 2010