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

Labeyrie, G. and Walker, J. G.M. and Robb, G. R.M. and Kaiser, R. and Ackemann, T. (2022) Ground-state coherence versus orientation : competing mechanisms for light-induced magnetic self-organization in cold atoms. Physical Review A, 105 (2). 023505. ISSN 2469-9926 (https://doi.org/10.1103/PhysRevA.105.023505)

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Abstract

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 Δm=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.