Resonance and Rectification in a Two-Dimensional Frenkel–Kontorova Model with Triangular Symmetry

The mode-locking phenomena in the dc- and ac-driven overdamped two-dimensional Frenkel–Kontorova model with triangular symmetric structures are studied. The obtained results show that the transverse velocity <v_x> increases in a series of quantized steps nμ_x (n=0, 1, 2, 3 ⋅⋅⋅). Moreover, the positive or negative rectification of longitudinal velocity <v_y> can occur when n is an odd number. It is also found in our simulations that the critical depinning force oscillates with the amplitude of ac-driven force, i.e., the system is dominated by the ac-driven force. The oscillatory behavior is strongly determined by the initial phase of ac force.