Anisotropic semi-vortices in dipolar spinor condensates controlled by Zeeman splitting

Abstract

Spatially anisotropic solitary vortices (AVSs), supported by anisotropic dipole-dipole interactions, were recently predicted in spin-orbit-coupled binary Bose-Einstein condensates (BECs), in the form of two-dimensional semi-vortices (complexes built of zero-vorticity and vortical components). We demonstrate that the shape of the AVSs -- horizontal or vertical, with respect to the in-plane polarization of the atomic dipole moments in the underlying BEC -- may be effectively controlled by strength $Ω$ of the Zeeman splitting (ZS). A transition from the horizontal to vertical shape with the increase of $Ω$ is found numerically and explained analytically. At the transition point, the AVS assumes the shape of an elliptical ring. Mobility of horizontal AVSs is studied too, with a conclusion that, with the increase of $Ω$, their negative effective mass changes the sign into positive via a point at which the effective mass diverges. Lastly, we report a new species of \textit{inverted} AVSs, with the zero-vorticity and vortex component placed in lower- and higher-energy components, as defined by the ZS. They are excited states, with respect to the ground states provided by the usual AVSs. Quite surprisingly, inverted AVSs are stable in a large parameter region.