The spin-excitation continuum, expected to dominate the low-energy fluctuation spectrum in the Haldane spin chain around the Brillouin zone center, $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ , is directly observed by inelastic magnetic neutron scattering in the $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ quasi-1D antiferromagnet ${\mathrm{CsNiCl}}_{3}$ . We find that the single mode approximation fails, and that a finite energy width appears in the dynamic correlation function $S(q,\ensuremath{\omega})$ for $q\ensuremath{\lesssim}0.5\ensuremath{\pi}$. The width increases with decreasing $q$ , while $S(q,\ensuremath{\omega})$ acquires an asymmetric shape qualitatively similar to that predicted for the two-magnon continuum in the nonlinear $\ensuremath{\sigma}$-model.The spin-excitation continuum, expected to dominate the low-energy fluctuation spectrum in the Haldane spin chain around the Brillouin zone center, $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$, is directly observed by inelastic magnetic neutron scattering in the $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ quasi-1D antiferromagnet ${\mathrm{CsNiCl}}_{3}$. We find that the single mode approximation fails, and that a finite energy width appears in the dynamic correlation function $S(q,\ensuremath{\omega})$ for $q\ensuremath{\lesssim}0.5\ensuremath{\pi}$. The width increases with decreasing $q$, while $S(q,\ensuremath{\omega})$ acquires an asymmetric shape qualitatively similar to that predicted for the two-magnon continuum in the nonlinear $\ensuremath{\sigma}$-model.

arXiv:cond-mat/0010049Physical Review LettersJun 15, 200173 citations

QUASI-CLASSICAL APPROXIMATION FOR THE PHASES OF SCATTERING

G. V. Dubrovskiǐ

Nov 1, 19640 citations

Three-particle scattering continuum in quasi-one-dimensional integer-spin Heisenberg magnets

Fabian H. L. Eßler

We analyze the three-particle scattering continuum in quasi-one-dimensional integer spin Heisenberg antiferromagnets within a low-energy effective field theory framework. We exactly determine the zero-temperature dynamical structure factor in the O(3) nonlinear \ensuremath{\sigma} model and in Tsvelik's Majorana fermion theory. We study the effects of interchain coupling in a random phase approximation. We discuss the application of our results to recent neutron-scattering experiments on the spin-1 Haldane-gap material ${\mathrm{CsNiCl}}_{3}.$ We analyze the three-particle scattering continuum in quasi-one-dimensional integer spin Heisenberg antiferromagnets within a low-energy effective field theory framework. We exactly determine the zero-temperature dynamical structure factor in the O(3) nonlinear \ensuremath{\sigma} model and in Tsvelik's Majorana fermion theory. We study the effects of interchain coupling in a random phase approximation. We discuss the application of our results to recent neutron-scattering experiments on the spin-1 Haldane-gap material ${\mathrm{CsNiCl}}_{3}.$

arXiv:cond-mat/9908186Physical review. B, Condensed matterAug 1, 200028 citations

The spin-excitation continuum, expected to dominate the low-energy fluctuation spectrum in the Haldane spin chain around the Brillouin zone center,

q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0

, is directly observed by inelastic magnetic neutron scattering in the

S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1

quasi-1D antiferromagnet

{\mathrm{CsNiCl}}_{3}

. We find that the single mode approximation fails, and that a finite energy width appears in the dynamic correlation function $S(q,\ensuremath{\omega})$ for $q\ensuremath{\lesssim}0.5\ensuremath{\pi}$. The width increases with decreasing

q

, while $S(q,\ensuremath{\omega})$ acquires an asymmetric shape qualitatively similar to that predicted for the two-magnon continuum in the nonlinear $\ensuremath{\sigma}$-model.

{\mathrm{CsNiCl}}_{3}.