Saturation effects in ac + dc driven Frenkel–Kontorova model

Properties of the Shapiro steps in different commensurate structures of the ac + dc driven Frenkel–Kontorova model with asymmetric deformable substrate potential have been examined. Deviation from the sinusoidal potential produces appearance of large subharmonic steps. In general, different commensurate structures respond differently to the applied force and have different velocities. The results have shown that after shape parameter gets some critical value, there is no difference in the behavior of Shapiro steps for different commensurate structures. The step size and the critical depinning force for different commensurate structures saturate to the same values, due to reduction of degrees of freedom with the large deformation of potential.