Soliton bound-states in dimerized spin chains

Abstract

In the beginning of the eighties Faddeev and Takhtajan [1] suggested that the fundamental excitations of the one-dimensional Heisenberg model should be viewed as massless kink-like s = 1/2 objects, the so called spinons. Although this is not the only way to think of the excitations in the Heisenberg model it is often a quite useful picture. A natural generalization of the Heisenberg model is to include a next-nearest neighbor term Si · Si+2 of strength J2, resulting in the following Hamiltonian: