Light-matter interactions are at the core of cold atoms experiments. A laser shined at atoms close to their resonance will apply a scattering force on them, and an inhomogeneous laser beam far from resonance will apply a dipole force.

We report the observation of the force applied to atoms when shined on by an intense, far detuned homogenous laser beam. This force, which effectively makes the atomic cloud self-interact, acts perpendicular to the laser beams direction and depends on the atomic cloud density profile. We refer to this force as electrostriction, since it resembles shape changes of materials under the application of a static electric field.

We demonstrate basic features of electrostriction and point out interesting consequences of this exotic force, such as self-trapping, modulational instability and effective inter-particle interaction tuning.