Generation of matter waves in Bose-Bose mixtures with helicoidal spin-orbit coupling

The paper studies the modulational instability (MI), both theoretically and numerically, of the helicoidal spin-orbit coupled Bose-Bose mixture. An expression of the MI growth rate is found through the linear stability analysis of continuous wave, followed by a comprehensive parametric study of the MI regions, emphasizing the effects of the spin-orbit coupling, the helicoidal gauge potential, and interatomic interactions. Direct numerical simulations concur with the analytical predictions. Under suitable balance between nonlinear and dispersive effects, trains of solitonlike objects are obtained, and their behaviors are very sensitive to parameter variations. Attention is particularly paid to the impact of the left- and right-handed helicoidal spin-orbit couplings on the appearance of matter waves that have the form soliton molecules in the Bose-Bose mixture. Additionally, for qualitative support of the obtained structures, the formation of a bright solitons train is also reported numerically using two neighboring solitons subjected to a fixed phase difference. Their behavior under the action of the helicoidal spin-orbit coupling is also debated, especially when left- and right-handed helicoidal couplings are interchanged.