2015/04/30 by Maxime Dugave, Frank Göhmann, Karol K. Kozlowski +2
Mathematics · Physics and Astronomy · #Algebraic number #Algebraic structures and combinatorial models #Antiferromagnetism #Bethe ansatz #Chain (unit) #Eigenvalues and eigenvectors #Matrix (chemical analysis) #Nonlinear system #Physics of Superconductivity and Magnetism #Quantum #Quantum many-body systems #Spectrum (functional analysis) #Transfer matrix #cond-mat.stat-mech #cond-mat.str-el #hep-th #math-ph #math.MP
paper · pdf · doi:10.1088/1751-8113/48/33/334001
published as J. Phys. A 48 (2015) 334001 (38pp) · 38 pages, dedicated to Prof. R. J. Baxter on the occasion of his 75th birthday, v2: minor typos corrected
arxiv created 2015/06/16 · openalex publication_date 2015/07/28 · openalex created_date 2016/06/24 · arxiv updated 2017/08/15 · openalex updated_date 2026/08/05
We consider the spectrum of correlation lengths of the spin− XXZ chain in the antiferromagnetic massive regime. These are given as ratios of eigenvalues of the quantum transfer matrix of the model. The eigenvalues are determined by integrals over certain auxiliary functions and by their zeros. The auxiliary functions satisfy nonlinear integral equations. We analyse these nonlinear integral equations in the low-temperature limit. In this limit we can determine the auxiliary functions and the expressions for the eigenvalues as functions of a finite number of parameters which satisfy finite sets of algebraic equations, the so-called higher-level Bethe ansatz equations. The behaviour of these equations, if we send the temperature T to zero, is different for zero and non-zero magnetic field h . If h is zero the situation is much like in the case of the usual transfer matrix. Non-trivial higher-level Bethe ansatz equations remain which determine certain complex excitation parameters as functions of hole parameters which are free on a line segment in the complex plane. If h is non-zero, on the other hand, a remarkable restructuring occurs, and all parameters which enter the description of the quantum transfer matrix eigenvalues can be interpreted entirely in terms of particles and holes which are freely located on two curves when T goes to zero.