Date of Original Version
We present a new approach to the low temperature dynamics of a quantum Heisenberg antiferromagnetic chain, which employs a combination of techniques: exact finite chain calculations; exact Bethe Ansatz calculations; and exact sum rules and selection rules. A striking property of the selection rules is that the contribution of several classes of states to the dynamics in non-zero field for finite systems is shown to vanish in the thermodynamic limit. Many novel quantum field-dependent effects appear such as soft modes, and multiple peak structure in the structure factor, which should be experimentally observable.
Müller, G., Thomas, H., Beck, H., & Bonner, J. C. (1981). Magnetic field effects on the spin dynamics of the linear spin-1/2 Heisenberg antiferromagnet. Solid State Commun., 38(1), 1-5. doi: 10.1016/0038-1098(81)91151-0
Available at: http://dx.doi.org/10.1016/0038-1098(81)91151-0