The Formation of Phase Structure in the Creation of Soliton Trains*

Matter-wave soliton trains were initially observed following an interaction quench in a condensate of ${^{7}\mathrm{Li}}$ atoms\footnote{K.E. Strecker, G.B. Partridge, A. G. Truscott, \& R. G. Hulet, Nature 417, 150 (2002).}. The relative phase between neighboring solitons was inferred to differ by $\pi$, giving the appearance of a repulsive interaction between them. The process by which this phase structure is formed is unknown. Starting with a condensate of ${^{7}\mathrm{Li}}$ atoms in the $|1,1\rangle$ state, we study the initial formation of soliton trains by quenching the magnetic field to rapidly vary the interaction from repulsive to attractive in a quasi-$1$-D system. We study the dynamics of the system shortly after the quench, using multiple in situ images. We previously used this technique to study soliton-soliton collisions\footnote{J. H. V. Nguyen, P. Dyke, D. Luo, B. A. Malomed, \& R. G. Hulet, Nature Physics 10, 918 (2014).}.