Date of Original Version
We present an analytical expression for the dynamical spin-correlation function of the S=1/2 linear Heisenberg antiferromagnet based on the fact that the spectrum is dominated by a double continuum of spin-wave excitations. Our expression is not exact, but exact sum rules show that the degree of approximation is small. We predict that in a uniform magnetic field the spectral weight function will display a double-peaked structure. Such a feature is observed in recent neutron-scattering experiments.
Müller, G., Beck, H. & Bonner, J. C.. Zero-temperature dynamics of the s=1/2 linear Heisenberg antiferromagnet. Phys. Rev. Lett. 43 (1979), 75-78.
Available at: http://dx.doi.org/10.1103/PhysRevLett.43.75.