# Finite-Temperature Dynamics and Thermal Intraband Magnon Scattering in Haldane Spin-One Chains

## TL;DR

This paper investigates the finite-temperature dynamical properties of Haldane spin-one chains, revealing thermal activation of intra-band magnon scattering and localized edge-states through advanced numerical simulations.

## Contribution

It provides the first detailed analysis of thermal spectral functions in spin-one chains using combined numerical methods, highlighting intra-band magnon scattering effects.

## Key findings

- Observation of a sub-gap band indicating edge-states
- Thermal activation of low-energy continuum in spectral functions
- Intra-band magnon scattering due to thermal population

## Abstract

The antiferromagnetic spin-one chain is considerably one of the most fundamental quantum many-body systems, with symmetry protected topological order in the ground state. Here, we present results for its dynamical spin structure factor at finite temperatures, based on a combination of exact numerical diagonalization, matrix-product-state calculations and quantum Monte Carlo simulations. Open finite chains exhibit a sub-gap band in the thermal spectral functions, indicative of localized edge-states. Moreover, we observe the thermal activation of a distinct low-energy continuum contribution to the spin spectral function with an enhanced spectral weight at low momenta and its upper threshold. This emerging thermal spectral feature of the Haldane spin-one chain is shown to result from intra-band magnon scattering due to the thermal population of the single-magnon branch, which features a large bandwidth-to-gap ratio. These findings are discussed with respect to possible future studies on spin-one chain compounds based on inelastic neutron scattering.