We investigate composite gap solitons in a spin-orbit-coupled condensate confined in an asymmetric bichromatic superlattice with a spatially modulated nonlinearity. Although the lattice lacks exact symmetry, fundamental and dipole-type solitons retain approximate parity-symmetric profiles and remain stable over a broad portion of the first band gap. Their finite-amplitude response is examined by applying population-imbalance and relative-phase perturbations to stationary fundamental states. As the nonlinear modulation strength increases, the population-imbalance oscillations evolve continuously from compact self-trapped motion to broader oscillations about a finite mean imbalance, accompanied by a monotonic increase of the critical initial population imbalance required for self-trapping and no abrupt destabilization. The density profiles remain strongly localized throughout, with only minor shape and center-of-mass variations, indicating that the crossover is an internal reorganization. Near $V_3=1$, the single-hump state persists as the local nonlinearity weakens, while for $V_3>1$, the single-hump branch folds near $V_3\simeq 1.05$ and an independent three-hump state appears at $V_3=1.50$, remaining localized under finite perturbation. These results demonstrate composite gap solitons that remain localized under finite perturbations, with tunable internal population dynamics and a nonlinearity-controlled number of occupied lattice regions in asymmetric nonlinear superlattices.

Close

PrevNext

View figure in article

• Bose-Einstein condensates
• Cold and ultracold molecules
• Cold gases in optical lattices