Effects of temperature dependent spin wave damping in the two-dimensional Hubbard antiferromagnet

Effects of the temperature dependent damping energy for spin waves in the long-range antiferromagnetic (AF) state of the generalized N-orbital (S = 12) Hubbard model at half filling is discussed. Thermally excited spin waves acquire a finite lifetime via (1) interactions between spin waves and (2) scattering due to AF domain boundaries. The damping energy Γsw due to (1) and (2) increases with T as T2 and e−2πρ3/T ∝ ξ−1 (inverse spin-spin correlation length), respectively. These T dependences for Γsw suggest that the contribution from the interaction between long wavelength spin waves is dominant for T < To, but the contribution from the domain boundary scattering becomes dominant for T > To. Both ζ and Γsw, respectively, provides a natural length and low energy cutoff scale for the macroscopic response of spins at intermediate temperatures. We discuss the consequence of the T dependent Γsw in the high-Tc copper oxides.