Multiparticle States in theS=1Chain SystemCsNiCl3

Abstract

A continuum of magnetic states has been observed by neutron scattering from the spin-1 chain compound CsNiCl3 in its disordered gapped one-dimensional phase. Results using both triple-axis and time-of-flight spectrometers show that around the antiferromagnetic point Qc = pi, the continuum lies higher in energy than the Haldane gapped excitations. At 6 K the integrated intensity of the continuum is about 12(2)% of the total spectral weight. This result is considerably larger than the 1%-3% weight predicted by the nonlinear sigma model for the three-particle continuum.

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

“…background subtraction. Another relevant quantity as far as the experiments of [1] are concerned, is the ratio of three and one magnon spectral weights for q = 0. We find that e.g.…”

“…In section III we study the effects of the coupling between chains in (1), using the NLσM results as an input. In section IV we determine the structure factor within a second low-energy effective field theory description, which holds for S = 1 in the presence of a (strong) biquadratic exchange interaction [6] between spins in addition to (1). Although the structure of the excitation spectrum as a function of wave number along the chain direction is essentially the same as in the NLσM , the structure factor turns out to be rather different.…”

“…In recent inelastic neutron scattering experiments [1] on the quasi one dimensional spin-1 Heisenberg magnet CsNiCl 3 [2], the existence of incoherent multiparticle scattering continua in the one dimensional phase was investigated. If was found, that close to the antiferromagnetic wave vector (along the chain direction), there is significant spectral weight above the coherent magnon peak.…”

Higgs mode and its decay in a two-dimensional antiferromagnet

“…2b) is kinematically restricted away from the ordering wavevector, and the Higgs mode is well identified at q = (0,0). Although continuum structures are generic to lowdimensional quantum magnets (for example, Haldane chains 27,28 ), the present case is distinct because the continuum structure near q = (π,π) is derived from a Higgs mode that exists as a well-defined quasiparticle away from the ordering wavevector.…”

“…In particular, it is uncertain at this point whether the decay process considered above fully describes its dynamics. In addition to the multimagnon continuum [27][28][29][30] , other channels such as decays into vortex-like excitations are conceivable in two-dimensional planar magnets and require further investigation. It would be also interesting to compare the results presented herein with the spectra from resonant inelastic X-ray scattering, which can in principle access both the scalar and longitudinal susceptibilities.…”