Model for the Magnetic Order and Pairing Channels in Fe Pnictide Superconductors

TL;DR

This study uses a two-orbital model and computational methods to analyze magnetic order and pairing mechanisms in Fe-pnictide superconductors, revealing stable magnetic states and dominant pairing operators with specific orbital symmetries.

Contribution

It introduces a detailed two-orbital model with derived hopping parameters and identifies stable magnetic states and dominant pairing channels in Fe-pnictide superconductors.

Findings

Spin striped state stable in undoped regime

Identification of dominant inter-orbital pairing operators

Pairing operators transform according to specific symmetry representations

Abstract

A two-orbital model for Fe-pnictide superconductors is investigated using computational techniques on two-dimensional square clusters. The hopping amplitudes are derived from orbital overlap integrals, or by band structure fits, and the spin frustrating effect of the plaquette-diagonal Fe-Fe hopping is remarked. A spin 'striped' state is stable in a broad range of couplings in the undoped regime, in agreement with neutron scattering. Adding two electrons to the undoped ground state of a small cluster, the dominant pairing operators are found. Depending on parameters, two pairing operators were identified: they involve inter-xz-yz orbital combinations forming spin singlets or triplets, transforming according to the B_2g and A_2g representations of the D_4h group, respectively.