Shaping an ultracold atomic soliton in a travelling wave laser beam

Fakultät für Physik der Universität Konstanz, Postfach 5560 M 674, D-78434 Konstanz, Germany

Corresponding authors: holzmann@lps.ens.fr Juergen.Audretsch@uni-konstanz.de

Received: 27 February 1997
Accepted: 2 September 1997

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 Schrödinger 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.