Anisotropy in s-wave Bose-Einstein condensate collisions and its relationship to superradiance

Piotr Deuar (1) , Jean-Christophe Jaskula (2) , Marie Bonneau (2) , Valentina Krachmalnicoff (2) , Denis Boiron (2) , Christoph I. Westbrook (2) , Karen V. Kheruntsyan (3)

1 Institut of Physics
2 Laboratoire Charles Fabry / Optique atomique
3 ARC CENTRE OF EXCELLENCE FOR QUANTUM-ATOM OPTICS - ARC Centre of Excellence for Quantum-Atom Optics

We report the experimental realization of a single-species atomic four-wave mixing process with BEC collisions for which the angular distribution of scattered atom pairs is not isotropic, despite the collisions being in the s-wave regime. Theoretical analysis indicates that this anomalous behavior can be explained by the anisotropic nature of the gain in the medium when the source clouds are not cylindrically symmetric around the collision axis. There are two competing anisotropic processes: classical trajectory deflections due to the mean-field potential, and Bose enhanced scattering. The bosonic enhancement process bears similarity to superradiance, although a consideration of the differences explains why it is more difficult to achieve strongly dominant end-fire modes with atom optics.

Mots clés: Bose-Einstein condensate; four wave mixing; amplification; collision; superradiance

Domaines: Gaz Quantiques [cond-mat.quant-gas]; Optique [physics.optics]

Piotr Deuar, Jean-Christophe Jaskula, Marie Bonneau, Valentina Krachmalnicoff, Denis Boiron, et al.. Anisotropy in s-wave Bose-Einstein condensate collisions and its relationship to superradiance. Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2014, 90, pp.033613. ⟨10.1103/PhysRevA.90.033613⟩. ⟨hal-01016111⟩