Dynamics and Collisions of domain wall bimerons in a spin–orbit-coupled Bose–Einstein Condensates

We investigate the dynamics and collisions of domain wall (DW) bimerons in spin–orbit-coupled two-component Bose–Einstein condensates (BECs). By adjusting the strengths of spin–orbit and Rabi couplings to control the DW size, we observe that an elongated DW undergoes rotation, fragmentation, oscillation, and stabilization processes, ultimately forming short DWs that remain stable. We also numerically investigate stable moving solitons and binary collisions between them. The shapes of the moving solitons become another type of soliton instead of the DW bimeron as the current spin–orbit-coupled system lacks invariance under Galilean transformations. At low velocities, collisions between soliton pairs with zero or π phase difference cause the pairs to collapse or rebound. At high velocities, solitons pass through each other; however, when the phase difference is π/2 or 3π/2, some particles from one soliton are attracted to the other, and this effect vanishes as the velocity increases further. Furthermore, in collisions between the soliton and DW bimeron, they transform into each other, accompanied by momentum conversion. In order to study the collisions of the DW bimerons, we stabilize the moving DW bimerons by applying an external magnetic field. The two DWs become misaligned, then connected, merged, rotated, and elongated. Ultimately, the two segments separate and move in opposite directions, deviating from their initial trajectories. Our results suggest a way of studying the collisions of DW bimerons in BECs.