Low Temperature Dynamics of Magnons in a Spin-1/2 Ladder Compound

TL;DR

This study investigates magnon behavior at low temperatures in a spin-1/2 ladder compound using advanced spectroscopy, revealing deviations from theoretical models due to anisotropies and impurities.

Contribution

It provides detailed experimental insights into magnon dynamics at low temperatures, highlighting deviations from existing theoretical predictions in one-dimensional quantum magnets.

Findings

Magnon energy and linewidth measured at low T.

Deviations from non-linear sigma model predictions.

Effects of anisotropies and impurities on magnon behavior.

Abstract

We have used a combination of neutron resonant spin-echo and triple-axis spectroscopies to determine the energy, fine structure, and linewidth of the magnon resonance in the model spin-1/2 ladder antiferromagnet IPA-CuCl_3 at temperatures T << Delta_0 /k_B, where Delta_0 is the spin gap at T=0. In this low-temperature regime we find that the results deviate substantially from the predictions of the non-linear sigma model proposed as a description of magnon excitations in one-dimensional quantum magnets and attribute these deviations to real-space and spin-space anisotropies in the spin Hamiltonian as well as scattering of magnon excitations from a dilute density of impurities. These effects are generic to experimental realizations of one-dimensional quantum magnets.