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Continuum in the spin excitation spectrum of a Haldane chain, observed by neutron scattering in CsNiCl3

I. A. Zaliznyak·S. -H. Lee·S. V. Petrov
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Abstract

The spin excitation continuum, expected to dominate the low-energy fluctuation spectrum in the Haldane spin chain around the Brillouin zone center, q=0, is directly observed by inelastic magnetic neutron scattering in the S=1 quasi-1D antiferromagnet CsNiCl3. We find that the single mode approximation fails, and that a finite energy width appears in the dynamic correlation function S(q,omega) for q < 0.5pi. The width increases with decreasing q, while S(q,omega) acquires an asymmetric shape qualitatively similar to that predicted for the 2-magnon continuum in the nonlinear sigma-model.

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I. A. Zaliznyak, S. -H. Lee, S. V. Petrov. 2000-10-03. Continuum in the spin excitation spectrum of a Haldane chain, observed by neutron scattering in CsNiCl3. https://doi.org/10.1103/physrevlett.87.017202

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