Spin Dynamics in the Two-Dimensional Spin 1/2 Heisenberg Antiferromagnet

We present low-temperature dynamic properties of the quantum two-dimensional antiferromagnetic Heisenberg model with spin S=1/2. The calculation of the dynamic correlation function is performed by combining a projection operator formalism and the modified spin-wave theory (MSW), which gives a gap in the dispersion relation for finite temperatures. The so calculated dynamic correlation function shows a double peak structure.We also obtain the spin-wave damping and compare our results to experimental data and to theoretical results obtained by other authors using different approaches.