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Motivated by field-theoretic predictions we investigate the stable excitations that exist in two characteristic gapped phases of a spin-1 model with Ising-like and single-ion anisotropies. The sine-Gordon theory indicates a region close to the phase boundary where a stable breather exists besides the stable particles, that form the Haldane triplet at the Heisenberg isotropic point. The numerical data, obtained by means of the Density Matrix Renormalization Group, confirm this picture in the so-called large-D phase for which we give also a quantitative analysis of the bound states using standard perturbation theory. However, the situation turns out to be considerably more intricate in the Haldane phase where, to the best of our data, we do not observe stable breathers contrarily to what could be expected from the sine-Gordon model, but rather only the three modes predicted by a novel anisotropic extension of the …
EDP sciences
Publication date: 
1 Sep 2006

L Campos Venuti, C Degli Esposti Boschi, Elisa Ercolessi, Giuseppe Morandi, Fabio Ortolani, Stefano Pasini, Marco Roncaglia

Biblio References: 
Volume: 53 Issue: 1 Pages: 11-18
The European Physical Journal B-Condensed Matter and Complex Systems