A deterministic origin for instabilities in a magneto-optical trap

The paper reports on the observation of a new type of instabilities in the atomic cloud of a magneto-optical trap (MOT). They appear as large amplitude self-oscillations, either periodic or erratic, depending on the parameters. An original model taking into account the shadow effect and an homogeneous distribution of the atoms in the cloud is developped. It allows us to show that these instabilities originate on the one hand from an anomalous Hopf bifurcation, and on the other hand from the extreme sensitivity of the system to noise.