Symbiotic gap and semi-gap solitons in Bose-Einstein condensates

TL;DR

This paper investigates one-dimensional gap solitons in binary Bose-Einstein condensates within optical lattices, exploring various types and transitions influenced by inter- and intra-species interactions through variational and numerical methods.

Contribution

It introduces a comprehensive analysis of symmetric, asymmetric, split, and intra- and inter-gap solitons, including their transitions, in binary Bose-Einstein condensates with optical lattices.

Findings

Multiple types of gap solitons identified, including symmetric, asymmetric, split, intra-gap, and inter-gap.

Transitions between different soliton states observed, especially with intra-species attraction.

Numerical and variational methods used to characterize soliton properties and behaviors.

Abstract

Using the variational approximation and numerical simulations, we study one-dimensional gap solitons in a binary Bose-Einstein condensate trapped in an optical-lattice potential. We consider the case of inter-species repulsion, while the intra-species interaction may be either repulsive or attractive. Several types of gap solitons are found: symmetric or asymmetric; unsplit or split, if centers of the components coincide or separate; intra-gap (with both chemical potentials falling into a single bandgap) or inter-gap, otherwise. In the case of the intra-species attraction, a smooth transition takes place between solitons in the semi-infinite gap, the ones in the first finite bandgap, and semi-gap solitons (with one component in a bandgap and the other in the semi-infinite gap).