On-demand generation of dark-bright soliton trains in Bose-Einstein condensates

Dark-bright (DB) solitons are fundamental macroscopic nonlinear excitations that arise in repulsive two-component Bose-Einstein condensates (BECs), whose dynamics and interactions are still an ongoing topic of interest and study.

In this work, we use the concept of matter-wave interference to controllably generate DB soliton trains in two-component BECs.

By choosing suitable filled box-type initial configurations (FBTCs) and solving the direct scattering problem for the defocusing vector nonlinear Schrödinger equation with nonzero boundary conditions, we obtain analytical expressions for the DB soliton solutions produced by a general FBTC.

Our findings show that the size of the initial box and the amount of filling directly affects the number, size, and velocity of the solitons, while the initial phase determines the parity (even or odd) of the solutions.

Moreover, we also perform a direct numerical integration of the coupled Gross-Pitaevskii equation, both in the absence and in the presence of a harmonic trap, and compare the results with the derived analytical expressions, obtaining an excellent agreement between the two.