Stochastic resonance in the two-dimensional q-state clock models

We numerically study stochastic resonance in the two-dimensional q-state clock models from q = 2 to 7 under a weak oscillating magnetic field. As in the mean-field case, we observe double resonance peaks, but the detailed response strongly depends on the direction of the field modulation for q >= 5 where the quasiliquid phase emerges. We explain this behavior in terms of free-energy landscapes on the two-dimensional magnetization plane.