Frequency oscillations of the Shapiro steps

The frequency dependence of the dynamical-mode locking phenomena in the ac driven dissipative Frenkel-Kontorova model is studied by the molecular-dynamics simulations. It was found that the Shapiro steps exhibit very strong frequency dependence influenced by the amplitude of ac force. At the low frequencies, in the large amplitude regime, the oscillations of the step width and the critical depinning force have been observed. These oscillations are directly related to the stability and the existence of the interference effects in the real systems. (c) 2007 American Institute of Physics.