Spin excitations in the nematic phase and the metallic stripe spin-density wave phase of iron pnictides

TL;DR

This paper investigates the evolution of magnetic excitations in iron pnictides, revealing how spin responses change with electronic correlations and symmetry breaking, highlighting differences between nematic and spin-density wave phases.

Contribution

It provides a comprehensive analysis of magnetic excitations in a five-orbital model, including the effects of correlations and nematic order, which was not extensively studied before.

Findings

Spin excitations evolve from broad low-energy modes to sharp spin waves with increasing interactions.

High-energy spin response depends qualitatively on interaction strength.

Nematic phase exhibits a pronounced C2 symmetric excitation spectrum above magnetic transition.

Abstract

We present a general study of the magnetic excitations within a weak-coupling five-orbital model relevant to itinerant iron pnictides. As a function of enhanced electronic correlations, the spin excitations in the symmetry broken spin-density wave phase evolve from broad low-energy modes in the limit of weak interactions to sharply dispersing spin wave prevailing to higher energies at larger interaction strengths. We show how the resulting spin response at high energies depends qualitatively on the magnitude of the interactions. We also calculate the magnetic excitations in the nematic phase by including an orbital splitting, and find a pronounced C_2 symmetric excitation spectrum right above the transition to long-range magnetic order. Finally, we discuss the C_2 versus C_4 symmetry of the spin excitations as a function of energy for both the nematic and the spin-density wave phase.