k=0 Excitations in the Quantum Chain Systems (C₆H₁₁NH₃)CuCl₃ and (C₆H₁₁NH₃)CuBr₃

Abstract

Recently, much theoretical effort has been devoted to the properties of ferromagnetic quantum (S=1/2) chains [1,2]. The excitation spectrum of Ising-Heisenberg chains has been shown to consist of magnons, magnon continua and magnon bound-states, of which the latter can be interpreted as the quantum analogue of classical envelope solitons [3,4]. For XY-Heisenberg quantum systems, the understanding of the excitation spectrum is less advanced [2,5], whereas in the classical limit these systems show a rich variety of non-linear phenomena, including soliton-like excitations [6]. The lower energy levels of the S=1/2 XYZ system in zero field have been obtained rigorously by mapping onto an eight-vertex model [7].