Dark soliton decay due to trap anharmonicity in atomic Bose-Einstein condensates

A number of recent experiments with nearly pure atomic Bose-Einstein condensates have confirmed the predicted dark soliton oscillations when under harmonic trapping. However, a dark soliton propagating in an inhomogeneous condensate has also been predicted to be unstable to the emission of sound waves. Although harmonic trapping supports an equilibrium between the co-existing soliton and sound, we show that the ensuing dynamics are sensitive to trap anharmonicities. Such anharmonicities can break the soliton-sound equilibrium and lead to the net decay of the soliton on a considerably shorter timescale than other dissipation mechanisms. Thus, we propose how small realistic modifications to existing experimental set-ups could enable the experimental observation of this decay channel.