Shaping an ultracold atomic soliton in a travelling wave laser beam

TL;DR

This paper derives a time-dependent nonlinear Schrödinger equation for ultracold atomic wave packets in a travelling laser wave, showing how acceleration and laser chirping can shape and control soliton forms.

Contribution

It introduces a novel effective nonlinear Schrödinger equation with time-dependent nonlinearity, enabling active control and shaping of atomic solitons under acceleration and laser frequency chirping.

Findings

Solitons can be adiabatically shaped during acceleration.

Laser chirping allows coherent control of soliton form.

The effective equation predicts damping or antidamping effects.

Abstract

An ultracold wave packet of bosonic atoms loaded into a travelling laser wave may form a many-atom soliton.This is disturbed by a homogeneous force field, for example by the inevitable gravitation. The wave packet is accelerated and therefore the laser frequency appears to be chirped in the rest frame of the atoms. We derive the effective nonlinear Schr\"odinger equation. It shows a time dependent nonlinearity coefficient which amounts to a damping or antidamping, respectively. The accelerated packet solution remains a soliton which changes its shape adiabatically. Similarly, an active shaping can be obtained in the force-free case by chirping the laser frequency thus representing a way of coherent control of the soliton form. The experimental consequences are discussed.