Negative radiation pressure in Bose-Einstein condensates

TL;DR

This paper investigates negative radiation pressure effects on dark and dark-bright solitons in Bose-Einstein condensates, revealing counter-intuitive forces due to negative effective mass, supported by numerical simulations and perturbative analysis.

Contribution

It demonstrates the occurrence of negative radiation pressure on solitons in Bose-Einstein condensates, highlighting novel force directions linked to negative effective mass phenomena.

Findings

Dark solitons experience acceleration opposite to incident waves when orthogonal component is involved.

Dark-bright solitons can accelerate in the same direction as the incoming wave, showing complex force interactions.

Negative radiation pressure effects are supported by numerical simulations and perturbative calculations.

Abstract

In two-component non-linear Schr\"odinger equations, the force exerted by incident monochromatic plane waves on an embedded dark soliton and on dark-bright-type solitons is investigated, both perturbatively and by numerical simulations. When the incoming wave is non-vanishing only in the orthogonal component to that of the embedded dark soliton, its acceleration is in the opposite direction to that of the incoming wave. This somewhat surprising phenomenon can be attributed to the well known "negative effective mass" of the dark soliton. When a dark-bright soliton, whose effective mass is also negative, is hit by an incoming wave non-vanishing in the component corresponding to the dark soliton, the direction of its acceleration coincides with that of the incoming wave. This implies that the net force acting on it is in the opposite direction to that of the incoming wave. This rather counter-intuitive effect is a yet another manifestation of negative radiation pressure exerted by the incident wave, observed in other systems. When a dark-bright soliton interacts with an incoming wave in the component of the bright soliton, it accelerates in the opposite direction, hence the force is "pushing" it now. We expect that these remarkable effects, in particular the negative radiation pressure, can be experimentally verified in Bose-Einstein condensates.