Incommensurability in the magnetic excitations of the bilinear-biquadratic spin-1 chain |
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Authors: | O Golinelli Th Jolicœur ES Sørensen |
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Institution: | (1) Service de Physique Théorique, CEA Saclay, 91191 Gif-sur-Yvette, France, FR;(2) Laboratoire de Physique Quantique, IRSAMC, Université Paul Sabatier, 31062 Toulouse Cedex 4, France, FR |
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Abstract: | We study the magnetic excitation spectrum of the spin-1 chain with Hamiltonian .We focus on the range where the spin chain is in the gapped Haldane phase. The excitation spectrum and static structure factor is studied using
direct Lanczos diagonalization of small systems and density-matrix renormalization group techniques combined with the single-mode
approximation. The magnon dispersion has a minimum at until a critical value is reached at which the curvature (velocity) vanishes. Beyond this point, which is distinct from the VBS point and the Lifshitz
point, the minimum lies at an incommensurate value that goes smoothly to when approaches , the Lai-Sutherland point. The mode remains isolated from the other states: there is no evidence of spinon deconfinement
before the point .These findings explain recent observation of the behavior of the magnetization curve for .
Received 16 December 1998 |
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Keywords: | PACS 75 10 Jm Quantized spin models - 75 20 Hr Local moment in compounds and alloys Kondo effect valence fluctuations heavy fermions |
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