Driven kink in the frenkel-kontorova model

The dynamics of dc driven chain of harmonically interacting atoms in the external sinusoidal potential (the Frenkel-Kontorova model) is studied. It is shown that in the underdamped case the motion of the topological soliton (kink) becomes unstable at a high velocity due to excitation of the localized intrinsic kink mode (the discrete shape mode, or discrete breather) in the kink tail. When the amplitude of the breather's oscillation becomes large enough, it decays into a kink-antikink pair. The subsequent collision of newly created kink and antikink leads to a sharp transition to the running state, where all atoms of the chain slide over the external potential almost freely.