Stability and dynamics of dark-bright solitons in spin-orbit- and Rabi-coupled binary Bose-Einstein condensates

TL;DR

This paper studies how synthetic gauge fields and interactions influence the stability and dynamics of dark-bright solitons in spin-orbit- and Rabi-coupled binary Bose-Einstein condensates, revealing complex nonlinear phenomena.

Contribution

It provides a comprehensive analysis of soliton stability and dynamics under synthetic gauge fields, including exact solutions, phase characterization, and nonlinear behavior in various regimes.

Findings

Exact dark-bright soliton solutions in the absence of spin-orbit coupling.

Spin-orbit coupling induces spin-dependent phase gradients and density oscillations.

Rabi coupling supports phase locking and breather-like excitations.

Abstract

We investigate the stability and nonlinear dynamics of dark-bright solitons in a one-dimensional binary Bose-Einstein condensate subjected to synthetic spin-orbit and Rabi couplings. In the absence of spin-orbit coupling, we map the coupled Gross-Pitaevskii equations onto the integrable Manakov model and obtain exact dark-bright soliton solutions, providing a rigorous theoretical benchmark. We demonstrate that finite spin-orbit coupling breaks integrability by inducing spin-dependent phase gradients, which result in spatial separation of the spin components and the emergence of intrinsic density oscillations. By contrast, Rabi coupling enforces phase locking between components and supports robust breather-like excitations. Using imaginary-time propagation together with Bogoliubov-de Gennes analysis, we systematically characterise ground-state phases and excitation spectra for both symmetric and asymmetric interaction regimes in homogeneous and harmonically trapped systems. Real-time simulations further demonstrate that finite gauge fields and interaction quenches drive the system far from equilibrium, giving rise to diverse nonlinear phenomena, including multi-soliton fragmentation, breathing stripe patterns, and soliton dynamics. Our results highlight the interplay of synthetic gauge fields, external confinement, and interaction engineering as powerful tools for controlling the stability and dynamical behaviour of nonlinear excitations in multicomponent quantum gases.