Dynamic Properties of a Two-Dimensional Heisenberg Antiferromagnet at Low Temperatures

By using a combination of hydrodynamics, scaling, and renormalization-group analysis, and a fit to the simulations of a classical rotor model, we can predict the form of the dynamic structure factor $S(\mathrm{k}, \omega )$ of a two-dimensional quantum Heisenberg antiferromagnet at low temperatures, if the zero-temperature spin-stiffness constant ${\rho }_s$ and magnetic susceptibility ${\chi }_{\perp }^0$ are known. These results should be applicable to inelastic neutron scattering in stoichiometric ${\mathrm{La}}_2$Cu${\mathrm{O}}_4$ above its Néel temperature, with only ${\rho }_s$ as an adjustable parameter.