Stability and dynamics of two-soliton molecules

TL;DR

This paper derives a generalized force formula for two solitons in a nonautonomous Gross-Pitaevskii equation, analyzing their interactions, stability, and the formation of soliton molecules under various conditions.

Contribution

It introduces a new generalized force formula for arbitrary soliton parameters and explores the stability and dynamics of soliton molecules.

Findings

Derived a formula for mutual soliton force considering amplitude, phase, and separation.

Identified conditions for stable soliton molecule formation and calculated its physical properties.

Analyzed stability of soliton molecules against various perturbations.

Abstract

The problem of soliton-soliton force is revisited. From the exact two solitons solution of a nonautonomous Gross-Pitaevskii equation, we derive a generalized formula for the mutual force between two solitons. The force is given for arbitrary solitons amplitude difference, relative speed, phase, and separation. The latter allows for the investigation of soliton molecules formation, dynamics, and stability. We reveal the role of the time-dependent relative phase between the solitons in binding them in a soliton molecule. We derive its equilibrium bond length, spring constant, frequency, effective mass, and binding energy of the molecule. We investigate the molecule's stability against perturbations such as reflection from surfaces, scattering by barriers, and collisions with other solitons.