Spontaneous time‐symmetry breaking in a vibrating cold atom system

M.-S. Heo, Y. Kim, H.-R. Noh and W. Jhe

in Fluctuating Nonlinear Oscillators

Published in print July 2012 | ISBN: 9780199691388
Published online September 2012 | e-ISBN: 9780191742255 | DOI:
Spontaneous time‐symmetry breaking in a vibrating cold atom system

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This chapter describes the experimental and theoretical studies of a spontaneous time-translation symmetry breaking transition in a non-equilibrium cold atom system. Such studies prepare two vibrating atomic clouds by periodically modulating the laser intensity in a magneto-optical trap (MOT). For a comparatively small total number of trapped atoms the clouds have equal populations, a consequence of fluctuation-induced inter-cloud transitions. As the total number of atoms is increased, spontaneous breaking of the discrete time-translation symmetry is observed with respect to the modulation period. The measured critical exponents and the frequency dispersion of the response show an ideal mean-field transition behaviour. The symmetry breaking is due to the modification of fluctuational dynamics by the interatomic interaction. The chapter provides a theoretical model based on the activation energy and master equation which explains the experimental results well. The enhancement of the fluctuation which cannot be described by the mean-field model, is also discussed.

Keywords: magneto-optical trap; non-equilibrium systems; time-translation symmetry breaking; critical exponent; ideal mean-field model; fluctuations; interatomic interaction

Chapter.  9426 words.  Illustrated.

Subjects: Mathematical and Statistical Physics

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