Date of Original Version
Having introduced the magnon in part I and the spinon in part II as the relevant quasi-particles for the interpretation of the spectrum of low-lying excitations in the one-dimensional (1D) s=1/2 Heisenberg ferromagnet and antiferromagnet, respectively, we now study the low-lying excitations of the Heisenberg antiferromagnet in a magnetic field and interpret these collective states as composites of quasi-particles from a different species. We employ the Bethe ansatz to calculate matrix elements and show how the results of such a calculation can be used to predict lineshapes for neutron scattering experiments on quasi-1D antiferromagnetic compounds. The paper is designed as a tutorial for beginning graduate students. It includes 11 problems for further study.
M. Karbach, K. Hu, and G. Müller. Introduction to the Bethe ansatz III.
This article is the third part of a series of papers designed as a tutorial for beginning graduate students. The first two articles were published in Computers in Physics (1997, 1998). This accepted manuscript from 2000 is the last article in the series.
Available at: http://arxiv.org/abs/cond-mat/0008018