Ground-state coherence versus orientation: Competing mechanisms for light-induced magnetic self-organization in cold atoms

We investigate the interplay between two mechanisms for magnetic self-organization in a cloud of cold rubidium atoms subjected to a retroreflected laser beam. The transition between two different phases, one linked to a spontaneous spatial modulation of the Am = 2 ground-state coherence and the other to that of the magnetic orientation (spin), can be induced by tuning either a weak transverse magnetic field or the laser intensity. We observe both first- and second-order transitions depending on the presence of the magnetic field. The experimental observations are successfully compared to extended numerical simulations based on a spin-1 model.

Automated summary

We investigate the interaction between two mechanisms for magnetic self-organization in a cloud of cold rubidium atoms. The transitions between different phases, induced by either a weak transverse magnetic field or laser intensity, are observed and characterized. The experimental observations are successfully compared to numerical simulations based on a spin-1 model.