High-resolution neutron and THz spectroscopies are used to study the magnetic excitation spectrum of Cs2CoBr4, a distorted-triangular-lattice antiferromagnet with nearly XY-type anisotropy. What was previously thought of as a broad excitation continuum [Phys. Rev. Lett. 129, 087201 (2022)] is shown to be a series of dispersive bound states reminiscent of "Zeeman ladders" in quasi-one-dimensional Ising systems. At wave vectors where inter-chain interactions cancel at the Mean Field level, they can indeed be interpreted as bound finite-width kinks in individual chains. Elsewhere in the Brillouin zone their true two-dimensional structure and propagation are revealed.
@article{arxiv.2301.13596,
title = {Confinement of fractional excitations in a triangular lattice antiferromagnet},
author = {L. Facheris and S. D. Nabi and A. Glezer Moshe and U. Nagel and T. Rõõm and K. Yu. Povarov and J. R. Stewart and Z. Yan and A. Zheludev},
journal= {arXiv preprint arXiv:2301.13596},
year = {2023}
}