SOLITON MOTION IN A PARAMETRICALLY AC-DRIVEN DAMPED TODA LATTICE

We demonstrate that a staggered parametric ac driving term can support stable progressive motion of a soliton in a Toda lattice with frictio n, while an unstaggered driving force cannot. A physical context of th e model is that of a chain of anharmonically coupled particles adsorbe d on a solid surface of a finite size. The ac driving force is generat ed by a standing acoustic wave excited on the surface. Simulations dem onstrate that the state left behind the moving soliton, with the parti cles shifted from their equilibrium positions, gradually relaxes back to the equilibrium state that existed before the passage of the solito n. The perturbation theory predicts that the ac-driven soliton exists if the amplitude of the drive exceeds a certain threshold. The analyti cal prediction for the threshold is in reasonable agreement with that found numerically. Collisions between two counterpropagating solitons is also simulated, demonstrating that the collisions are, effectively, fully elastic. [S1063-651X(98)07111-6].