Observation of Light-Induced Dipole-Dipole Forces in Ultracold Atomic Gases

TL;DR

This paper reports the experimental observation of light-induced dipole-dipole forces in ultracold rubidium gases, revealing a collective, nonlocal attraction that depends on atomic density gradients and is effective for both red and blue detunings.

Contribution

It provides the first experimental evidence of light-induced dipole-dipole interactions causing self-confinement in ultracold atomic gases, supported by a theoretical local-field model.

Findings

Observation of nonlocal attractive forces in ultracold gases

Force depends on atomic density gradient

Effective for both red and blue-detuned light

Abstract

We investigate an attractive force caused by light induced dipole-dipole interactions in freely expanding ultracold 87Rb atoms. This collective, light-triggered effect results in a self-confining potential with interesting features: it exhibits nonlocal properties, is attractive for both red and blue-detuned light fields and induces a remarkably strong force that depends on the gradient of the atomic density. The experimental data are discussed in the framework of a theoretical model based on a local-field approach for the light scattered by the atomic cloud.