Inelastic neutron scattering measurements are reported that show a new longitudinal mode in the antiferromagnetically ordered phase of the spin-1/2 quasi-one-dimensional antiferromagnet KCuF3. This mode signals the cross-over from one-dimensional to three-dimensional behavior and indicates a reduction in the ordered spin moment of a spin-1/2 antiferromagnet. The measurements are compared with recent quantum field theory results and are found to be in excellent agreement. A feature of the data not predicted by theory is a damping of the mode by decay processes to the transverse spin-wave branches.
@article{arxiv.cond-mat/9910459,
title = {A Novel Longitudinal Mode in the Coupled Quantum Chain Compound KCuF3},
author = {B. Lake and D. A. Tennant and S. E. Nagler},
journal= {arXiv preprint arXiv:cond-mat/9910459},
year = {2009}
}
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9 pages of text plus 4 postscript figures (1 color)