One-Dimensional spin model with arbitrary high power terms

Abstract

Basic spectral and thermodynamical properties of a spin chain (S=1/2) with a longitudinal — transverse anisotropy and nearest-neighbour interaction are considered, assuming the Hamiltonian to be a sum of arbitrary high power terms. After the renormalization of the spectrum, the rigorous solutions of the bilinear X-Y-model turn out to be stable with respect to the arbitrary high power terms. As to the low-excited and magnon-bound states in the spectrum of the system considered, they can be readily obtained from the known results for a “usual” bilinear anisotropic Heisenberg chain.