Strong Correlations and Magnetic Frustration in the High Tc Iron Pnictides

TL;DR

This paper explores how magnetic frustration and strong correlations in iron pnictides influence their magnetic and superconducting properties, highlighting the role of competing interactions and doping in promoting superconductivity with a specific d-wave symmetry.

Contribution

It introduces a theoretical framework linking magnetic frustration and proximity to a Mott insulator to the emergence of superconductivity in iron pnictides, emphasizing the orbital symmetry of the pairing.

Findings

Frustrated superexchange interactions lead to a collinear antiferromagnetic state.

Doping suppresses magnetic order and promotes superconductivity.

The favored superconducting order parameter has d_{xy} symmetry.

Abstract

We consider the iron pnictides in terms of a proximity to a Mott insulator. The superexchange interactions contain competing nearest-neighbor and next-nearest-neighbor components. In the undoped parent compound, these frustrated interactions lead to a two-sublattice collinear antiferromagnet (each sublattice forming a Neel ordering), with a reduced magnitude for the ordered moment. Electron or hole doping, together with the frustration effect, suppresses the magnetic ordering and allows a superconducting state. The exchange interactions favor a d-wave superconducting order parameter; in the notation appropriate for the Fe square lattice, its orbital symmetry is $d_{xy}$. A number of existing and future experiments are discussed in light of the theoretical considerations.