Motion of discrete solitons assisted by nonlinearity management

TL;DR

This paper shows that periodic nonlinearity modulation in a discrete nonlinear Schrödinger system can induce and control stable traveling solitons, with analytical predictions confirmed by extensive simulations and potential experimental realization.

Contribution

It introduces a method to generate and manipulate stable traveling solitons via nonlinearity management in the DNLS equation, supported by analytical and numerical analysis.

Findings

Periodic modulation facilitates creation of traveling solitons.

Stable solitons can move long distances without loss.

Velocity predictions match analytical resonance conditions.

Abstract

We demonstrate that periodic modulation of the nonlinearity coefficient in the discrete nonlinear Schr\"{o}dinger (DNLS) equation can strongly facilitate creation of traveling solitons in the lattice. We predict this possibility in an analytical form, and test it in direct simulations. Systematic simulations reveal several generic dynamical regimes, depending on the amplitude and frequency of the time modulation, and on initial thrust which sets the soliton in motion. These regimes include irregular motion, regular motion of a decaying soliton, and regular motion of a stable one. The motion may occur in both the straight and reverse directions, relative to the initial thrust. In the case of stable motion, extremely long simulations in a lattice with periodic boundary conditions demonstrate that the soliton keeps moving as long as we can monitor without any visible loss. Velocities of moving stable solitons are in good agreement with the analytical prediction, which is based on requiring a resonance between the ac drive and motion of the soliton through the periodic potential. All the generic dynamical regimes are mapped in the model's parameter space. Collisions between moving stable solitons are briefly investigated too, with a conclusion that two different outcomes are possible: elastic bounce, or bounce with mass transfer from one soliton to the other. The model can be realized experimentally in a Bose-Einstein condensate trapped in a deep optical lattice.