Dynamical structure factors in the nematic phase of frustrated ferromagnetic spin chains

TL;DR

This paper investigates the dynamical structure factors of the spin-nematic phase in frustrated ferromagnetic spin chains using advanced numerical methods, providing insights relevant for experimental scattering techniques.

Contribution

It extends the Tomonaga-Luttinger liquid theory to include gapped magnon excitations interacting with bound magnon pairs, offering a new theoretical framework.

Findings

Qualitative understanding of thresholds in structure factors

Numerical results match experimental scattering data

Extension of Luttinger liquid theory to magnon interactions

Abstract

Frustrated spin systems can show phases with spontaneous breaking of spin-rotational symmetry without the formation of local magnetic order. We study the dynamic response of the spin-nematic phase of one-dimensional spin-1/2 systems, characterized by slow large-distance decay of quadrupolar correlations, by numerically computing one-spin and two-spin dynamical structure factors at zero temperature using time-dependent density matrix renormalization group methods. We interpret the results in terms of an effective theory of gapped magnon excitations interacting with a quasi-condensate of bound magnon pairs. This employs an extension of the well-known Tomonaga-Luttinger liquid theory which includes the magnon states as a mobile impurity. A good qualitative understanding of the characteristic thresholds and their intensity in the structure factors is obtained this way. Our results are useful in the interpretation of inelastic neutron scattering and resonant inelastic x-ray scattering experiments.