Inelastic neutron scattering on deuterated single-crystal samples is used to study Haldane-gap excitations in the new S=1 one-dimensional quantum antiferromagnet NDMAP, that was recently recognized as an ideal model system for high-field studies. The Haldane gap energies Δx=0.42 meV, Δy=0.52 meV and Δz=1.86 meV, for excitations polarized along the a, b, and c crystallographic axes, respectively, are directly measured. The dispersion perpendicular to the chain axis c is studied, and extremely weak inter-chain coupling constants Jy=1.8⋅10−3 meV and Jx=3.5⋅10−4 meV, along the a and b axes, respectively, are determined. The results are discussed in the context of future experiments in high magnetic fields.
@article{arxiv.cond-mat/0003223,
title = {Haldane-gap excitations in the low-H_c 1-dimensional quantum antiferromagnet NDMAP},
author = {A. Zheludev and Y. Chen and C. L. Broholm and Z. Honda and K. Katsumata},
journal= {arXiv preprint arXiv:cond-mat/0003223},
year = {2009}
}