213 research outputs found
Excitation of zonal flow by the modulational instability in electron temperature gradient driven turbulence
The generation of large-scale zonal flows by small-scale electrostatic drift
waves in electron temperature gradient(ETG) driven turbulence model is
considered. The generation mechanism is based on the modulational instability
of a finite amplitude monochromatic drift wave. The threshold and growth rate
of the instability as well as the optimal spatial scale of zonal flow are
obtained.Comment: 10 pages, 3 figure
Continuum in the spin excitation spectrum of a Haldane chain, observed by neutron scattering in CsNiCl3
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.Comment: 4 pages, 3 figures, submitted to PR
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