Exact sum rules are obtained for the nearest-neighbor Heisenberg antiferromagnet and XY ferromagnet in one dimension. In the Heisenberg case the sum rules may be used to show that most of the spectral weight of the spin correlation function at small k and T=0 is concentrated near the frequency of the "des Cloizeaux-Pearson" states. In the XY case, the corresponding "Schultz-Lieb-Mattis" states only carry a negligible portion of the weight at small k.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics