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Superconductivity in Multi-orbital t-J1-J2 Model and its Implications for Iron Pnictides

By Pallab Goswami, Predrag Nikolic and Qimiao Si

Abstract

Motivated by the bad metal behavior of the iron pnictides, we study a multi-orbital $\mathrm{t-J_1-J_2}$ 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 $A_{1g}$ $s_{x^2y^2}$ channel, the nodal $A_{1g}$ $s_{x^2+y^2}$ and $B_{1g}$ $d_{x^2-y^2}$ channels are also competitive in the magnetically frustrated $J_1 \sim J_2$ parameter regime. An $A_{1g}+i B_{1g}$ 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.Comment: 5 pages, 3 figures, to appear in EP

Topics: Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons
Publisher: 'IOP Publishing'
Year: 2010
DOI identifier: 10.1209/0295-5075/91/37006
OAI identifier: oai:arXiv.org:0905.2634

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