Solitons of the coupled Schr\"odinger - Korteweg - de Vries system with arbitrary strengths of the nonlinearity and dispersion

TL;DR

This paper introduces new two-component soliton solutions in a coupled Schrödinger-KdV system with arbitrary nonlinearity and dispersion strengths, analyzing their dynamics, collisions, and approximate analytical forms.

Contribution

It provides novel analytical and numerical solutions for coupled solitons with arbitrary parameters, including inelastic collision behavior and intrinsic mode excitation.

Findings

Multiple soliton formations depending on dispersion strength

Inelastic collisions with soliton amplification or attenuation

Existence of approximate and exact two-component soliton solutions

Abstract

New two-component soliton solutions of the coupled high-frequency (HF) - low-frequency (LF) system, based on Schr\"odinger - Korteweg - de Vries (KdV) system with the Zakharov's coupling, are obtained for arbitrary relative strengths of the nonlinearity and dispersion in the LF component. The complex HF field is governed by the linear Schr\"odinger equation with a potential generated by the real LF component, which, in turn, is governed by the KdV equation including the ponderomotive coupling term, representing the feedback of the HF field onto the LF component. First, we study the evolution of pulse-shaped pulses by means of direct simulations. In the case when the dispersion of the LF component is weak in comparison to its nonlinearity, the input gives rise to several solitons in which the HF component is much broader than its LF counterpart. In the opposite case, the system creates a single soliton with approximately equal widths of both components. Collisions between stable solitons are studied too, with a conclusion that the collisions are inelastic, with a greater soliton getting still stronger, and the smaller one suffering further attenuation. Robust intrinsic modes are excited in the colliding solitons. A new family of approximate analytical two-component soliton solutions with two free parameters is found for an arbitrary relative strength of the nonlinearity and dispersion of the LF component, assuming weak feedback of the HF field onto the LF component. Further, a one-parameter (non-generic) family of exact bright-soliton solutions, with mutually proportional HF and LF components, is produced too. Intrinsic dynamics of the two-component solitons, induced by a shift of their HF component against the LF one, is also studied, by means of numerical simulations, demonstrating excitation of a robust intrinsic mode