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Publication
Physical Review Letters
Paper
Excitation Spectrum of the Ising-Heisenberg Chain Ferromagnet
Abstract
Results are presented and interpreted for the zero- and finite-temperature excitation spectrum of ferromagnetic Ising-Heisenberg chains, as probed by dynamic form factors. Finite-chain calculations demonstrate the occurrence of a thermally induced resonance centered around zero frequency, and a broadening of the magnon and two-magnon bound-state resonances at low T. The occurrence of bound states in the associated transitions demonstrates the failure of finite-order magnon perturbation theory. © 1981 The American Physical Society.