title: Spontaneous four-wave mixing of de Broglie waves: beyond optics.
abstract: We investigate the atom-optical analog of degenerate four-wave mixing by colliding two Bose-Einstein condensates of metastable helium. The momentum distribution of the scattered atoms is measured in three dimensions. A simple analogy with photon phase matching conditions suggests a spherical final distribution. We find, however, that it is an ellipsoid with radii smaller than the initial collision momenta. Numerical and analytical calculations agree with this and reveal the interplay between many-body effects, mean-field interaction, and the anisotropy of the source condensate.
authors.affiliation: Laboratoire Charles Fabry de l'Institut d'Optique, Univ Paris Sud, CNRS, Campus Polytechnique RD128 91127 Palaiseau France.
authors.forename: V
authors.initials: V
authors.lastname: Krachmalnicoff
authors.forename: J-C
authors.initials: JC
authors.lastname: Jaskula
authors.forename: M
authors.initials: M
authors.lastname: Bonneau
authors.forename: V
authors.initials: V
authors.lastname: Leung
authors.forename: G B
authors.initials: GB
authors.lastname: Partridge
authors.forename: D
authors.initials: D
authors.lastname: Boiron
authors.forename: C I
authors.initials: CI
authors.lastname: Westbrook
authors.forename: P
authors.initials: P
authors.lastname: Deuar
authors.forename: P
authors.initials: P
authors.lastname: Ziń
authors.forename: M
authors.initials: M
authors.lastname: Trippenbach
authors.forename: K V
authors.initials: KV
authors.lastname: Kheruntsyan