Double stochastic resonance in the mean-field q-state clock model.

A magnetic system with a phase transition at temperature T(c) may exhibit double-resonance peaks under a periodic external magnetic field because the time scale matches the external frequency at two different temperatures, one above T(c) and the other below T(c). We study the double-resonance phenomena for the mean-field q-state clock model based on the heat-bath-type master equation. We find double peaks as observed in the kinetic Ising case (q = 2) for all q ≥ 4, but for the three-state clock model (q = 3), the existence of double peaks is possible only above a certain external frequency since it undergoes a discontinuous phase transition.