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

TL;DR

This paper investigates how Zeeman splitting influences the shape, mobility, and stability of anisotropic semi-vortices in dipolar spinor Bose-Einstein condensates, revealing controllable shape transitions and the existence of stable inverted semi-vortices.

Contribution

It introduces the control of AVS shape via Zeeman splitting and discovers stable inverted AVSs, expanding understanding of vortex dynamics in dipolar BECs.

Findings

Shape transition from horizontal to vertical AVSs with increasing Zeeman splitting

Negative effective mass of horizontal AVSs changes to positive at a critical Zeeman splitting

Stable inverted AVSs with zero-vorticity and vortex components in different energy states

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 $\Omega$ of the Zeeman splitting (ZS). A transition from the horizontal to vertical shape with the increase of $\Omega$ 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 $\Omega $, 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.