paper

Exact solution for the spin- XXZ quantum chain with non-diagonal twists

arXiv:hep-th/9502041 · doi:10.1016/0550-3213(95)00168-R

Abstract

We study integrable vertex models and quantum spin chains with toroidal boundary conditions. An interesting class of such boundaries is associated with non-diagonal twist matrices. For such models there are no trivial reference states upon which a Bethe ansatz calculation can be constructed, in contrast to the well-known case of periodic boundary conditions. In this paper we show how the transfer matrix eigenvalue expression for the spin- XXZ chain twisted by the charge-conjugation matrix can in fact be obtained. The technique used is the generalization to spin- of the functional relation method based on ``pair-propagation through a vertex''. The Bethe ansatz-type equations obtained reduce, in the case of lattice size , to those recently found for the Hofstadter problem of Bloch electrons on a square lattice in a magnetic field.

25 pages, LaTeX

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