2005/02/28 by Jun-ichi Igarashi, Tatsuya Nagao · 1 citation
Physics and Astronomy · #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.72.014403
published as Phys. Rev. B 72, pp.014403 (2005). · 20 pages, 6 figures, revised text, added curves in Figs. 3 and 6 for J'/J=0.075 and corrected typos in Tables
arxiv created 2005/04/26 · arxiv updated 2009/12/01
We study the effects of quantum fluctuations on excitation spectra in the two-dimensional Heisenberg antiferromagnet by means of the 1/S expansion. We calculate the spin-wave dispersion and the transverse dynamical structure factor up to the second order of 1/S in comparison with inelastic neutron scattering experiments. The spin-wave energy at momentum (π,0) is found to be about 2% smaller than that at (π/2,π/2) due to the second-order correction. In addition, we study the dimensional crossover from two dimensions to one dimension by weakening exchange couplings in one direction. It is found that the second-order correction becomes large with approaching the quasi-one dimensional situation and makes the spin-wave energy approach to the des Cloizeaux-Pearson boundary for S=1/2. The transverse dynamical structure factor is also calculated up to the second order of 1/S. It is shown that the intensity of spin-wave peak is strongly reduced while the intensity of three-spin-wave continuum becomes large and exceeds that of the spin-wave peak in the quasi-one dimensional situation.