Sublattice-symmetric spin-wave theory for the Heisenberg antiferromagnet

Dynamics of Antiferromagnetic Heisenberg Model at Low Temperatures

Dynamical correlation function Gr(t)=〈Sr(t)·S0(0)〉 and dynamical structure factor Sq(ω) for the Heisenberg antiferromagnet are calculated by the modified spin-wave theory. We use the Dyson-Maleev transformation, the ideal spin-wave states and the rotational averaging. The static correlation function Gr(t=0) coincides with that obtained in previous papers for the antiferromagnet. We rederive the Auerbach and Arovas dynamical structure factor. This satisfies the dynamic scaling hypothesis at low temperature and low momentum. Analytical form of dynamical scaling function is obtained. We find that the characteristic time τ is proportional to the correlation length ξ. In the classical limit our results are compared with the molecular dynamics calculation for 1D system. The agreement is good for the short time correlation, but it is not good for the long time correlation. This is in contrast to the agreement for a wide range of time in the case of ferromagnet. The analysis of magnetic susceptibility of La2CuO4 is given.