Thermal Intra-Band Magnon Scattering in Haldane Spin-One Chains

We present results from a thorough evaluation of the dynamical spin structure factor of the Haldane chain at finite temperatures,
based on a combination of exact numerical diagonalization,
finite-temperature density-matrix renormalization group calculations and quantum Monte Carlo simulations.
Simulations performed on finite open chains exhibit a sub-gap band in the thermal spin spectral function, indicative of the
localized edge-modes in the Haldane chain's ground state. Furthermore, we observe the thermal activation of a distinct low-energy contribution to
the spin spectral function with an enhanced spectral weight at low momenta that results from intra-band magnon scattering due to the thermal population of the single-magnon mode.
These findings are discussed with respect to previous results on the spin spectral function and possible future studies on
Haldane spin chain compounds based on inelastic neutron scattering experiments.