Dynamical generation of dark solitons in spin-orbit-coupled Bose-Einstein condensates

We numerically investigate the ground state, the Raman-driving dynamics, and the nonlinear excitations of a realized spin-orbit-coupled Bose-Einstein condensate in a 1D harmonic trap. Depending on the Raman coupling and the interatomic interactions, three ground-state phases are identified: stripe, plane wave, and zero-momentum phases. A narrow parameter regime with coexistence of stripe and zero-momentum or plane wave phases in real space is found. Several sweeps progress across different phases by driving the Raman coupling linearly in time are simulated and the nonequilibrium dynamics of the system in these sweeps are studied. We find several kinds of nonlinear excitations, with the particular dark solitons excited in the sweep from the stripe phase to the plane wave or zero-momentum phase within the trap. Moreover, the number and the stability of the dark solitons can be controlled in the driving, which provides a direct and easy way to generate dark solitons and study their dynamics and interaction properties. (C) 2015 Optical Society of America