Dipolar bright solitons and solitary vortices in a radial lattice

TL;DR

This paper demonstrates that a two-dimensional dipolar Bose-Einstein condensate in a radial lattice can support stable vortex solitons with high topological charges, which are typically unstable, by trapping them in different radial troughs.

Contribution

The study introduces a new method for stabilizing high-charge vortex solitons in dipolar BECs using a radially periodic potential, enabling stability up to S=11 and coexistence of multiple vortices.

Findings

High-charge vortex solitons are stable in the radial lattice system.

Multiple vortex solitons with different charges can coexist in separate troughs.

Fundamental solitons exhibit different density profiles depending on the potential phase.

Abstract

Stabilizing vortex solitons with high values of the topological charge, S, is a challenging issue in optics, studies of Bose-Einstein condensates (BECs) and other fields. To develop a new approach to the solution of this problem, we consider a two-dimensional dipolar BEC under the action of an axisymmetric radially periodic lattice potential, $V(r)\sim \cos (2r+\delta )$, with dipole moments polarized perpendicular to the system's plane, which gives rise to isotropic repulsive dipole-dipole interactions (DDIs). Two radial lattices are considered, with $\delta =0$ and $\pi $, i.e., a potential maximum or minimum at $r=0$, respectively. Families of vortex gapsoliton (GSs) with $S=1$ and $S\geq 2$, the latter ones often being unstable in other settings, are completely stable in the present system (at least, up to $S=11$), being trapped in different annular troughs of the radial potential. The vortex solitons with different $S$ may stably coexist in sufficiently far separated troughs. Fundamental GSs, with $S=0$, are found too. In the case of $\delta =0$, the fundamental solitons are ring-shaped modes, with a local minimum at $r=0.$At $\delta =\pi $, they place a density peak at the center.