Interactions of solitons with a Gaussian barrier: Splitting and recombination in quasi-1D and 3D

TL;DR

This study investigates the complex 3D interactions of matter-wave solitons with Gaussian barriers, revealing significant deviations from 1D models and highlighting effects relevant to soliton-based interferometry.

Contribution

It demonstrates the importance of 3D effects in soliton-barrier interactions and compares the effectiveness of NPSE and 3D GPE models over the 1D GPE.

Findings

Increased first reflection coefficient with higher barriers and fewer atoms

Strong modulation of reflection/recombination probabilities by barrier height

Asymmetry in transmitted and reflected oscillation amplitudes

Abstract

The interaction of matter-wave solitons with a potential barrier is a fundamentally important problem, and the splitting and subsequent recombination of the soliton by the barrier is the essence of soliton matter-wave interferometry. We demonstrate the three-dimensional (3D) character of the interactions in the case relevant to ongoing experiments, where the number of atoms in the soliton is sufficiently large that the soliton is close to collapse. The mean-field description is quite accurate, but the proximity to the collapse threshold makes the use of the 1D Gross-Pitaevskii equation (GPE) irrelevant. We examine the soliton dynamics in the framework of the effectively 1D nonpolynomial Schr{\"{o}}dinger equation (NPSE), which admits the collapse in a modified form, and in parallel we use the full 3D GPE. Both approaches produce results which are very different from those produced in recent work which used the 1D cubic GPE. The features observed in both the NPSE and the 3D GPE include (a) an increase in the first reflection coefficient for increasing barrier height and decreasing atom number; (b) strong modulation in the secondary reflection/recombination probability vs. barrier height; (c) a pronounced asymmetry in the oscillation amplitudes of the transmitted and reflected fragments; (d) an enhancement of the transverse excitations as the number of atoms is increased. We also explore effects produced by variations of the barrier width and outcomes of the secondary collision upon phase imprinting on the fragment in one arm of the interferometer.