Using Monte Carlo and spin-dynamics methods, we have investigated the dynamic behavior of the classical, antiferromagnetic XY model on a triangular lattice with linear sizes L≤300. The temporal evolutions of spin configurations were obtained by solving numerically the coupled equations of motion for each spin using fourth-order Suzuki-Trotter decompositions of exponential operators. From space- and time-displaced spin-spin correlation functions and their space-time Fourier transforms we obtained the dynamic structure factor S(q,w) for momentum q and frequency ω. Below TKT (Kosterlitz-Thouless transition), both the in-plane (Sxx) and out-of-plane (Szz) components of S(q,ω) exhibit very strong and sharp spin-wave peaks. Well above TKT, Sxx and Szz apparently display a central peak, and spin-wave signatures are still seen in Szz. In addition, we also observed an almost dispersionless domain-wall peak at high ω below Tc, (Ising transition), where long-range order appears in the staggered chirality. Above Tc, the domain-wall peak disappears for all q. The line shape of these peaks is captured reasonably well by a Lorentzian form. Using a dynamic finite-size scaling theory, we determined the dynamic critical exponent z = 1.002(3). We found that our results demonstrate the consistency of the dynamic finite-size scaling theory for the characteristic frequency ωm and the dynamic structure factor S(q,ω) itself.
|Original language||English (US)|
|Number of pages||7|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Nov 1 2002|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics