Spin waves in the block checkerboard antiferromagnetic phase

TL;DR

This paper theoretically investigates the spin wave properties and phase diagram of an extended Heisenberg model relevant to iron-based superconductors, revealing stable magnetic order and predicting neutron scattering patterns.

Contribution

It provides the first detailed analysis of spin wave spectra and magnetic phases in the block checkerboard antiferromagnetic state of the extended $J_1$-$J_2$ model for iron-based superconductors.

Findings

Block checkerboard antiferromagnetic order is stable in relevant parameter regions.

The spin wave spectrum includes two acoustic and six optical branches.

Predicted inelastic neutron scattering patterns for experimental verification.

Abstract

Motivated by the discovery of new family 122 iron-based superconductors, we present the theoretical results on the ground state phase diagram, spin wave and dynamic structure factor of the extended $J_{1}-J_{2}$ Heisenberg model. In the reasonable physical parameter region of $K_{2}Fe_{4}Se_{5}$, we fi{}nd the block checkerboard antiferromagnetic order phase is stable. There are two acoustic branches and six optical branches spin wave in the block checkerboard antiferromagnetic phase, which has analytic expression in the high symmetry points. To compare the further neutron scattering experiments, we discuss the saddlepoint structure in the magnetic excitation spectrum and calculate the predicted inelastic neutron scattering pattern based on linear spin wave theory.