Ground-state properties of spin-orbit-coupled dipolar Bose-Einstein condensates with in-plane gradient magnetic field

TL;DR

This paper explores the ground-state properties and spin textures of spin-orbit-coupled dipolar Bose-Einstein condensates under various interactions and fields, revealing complex phases and topological structures.

Contribution

It systematically analyzes how spin-orbit coupling, dipole-dipole interactions, and in-plane quadrupole fields influence ground states and spin textures in dipolar BECs, uncovering novel phases and topological phenomena.

Findings

Identification of quadrupole stripe and Thomas-Fermi phases with half-quantum vortices

Discovery of ring mixed phase with hidden vortex-antivortex clusters

Observation of criss-crossed vortex string and delaminated structures

Abstract

We investigate the ground-state properties of spin-orbit-coupled pseudo-spin-1/2 dipolar Bose-Einstein condensates (BECs) in a two-dimensional harmonic trap and an in-plane quadrupole field. The effects of spin-orbit coupling (SOC), dipole-dipole interaction (DDI) and the in-plane quadrupole field on the ground-state structures and spin textures of the system are systematically analyzed and discussed. For fixed SOC and DDI strengths, the system shows a quadrupole stripe phase with a half-quantum vortex, or a quadrupole Thomas-Fermi phase with a half-quantum antivortex for small quadrupole field strength, depending on the ratio between inter- and intraspecies interaction. As the quadrupole field strength enhances, the system realizes a ring mixed phase with a hidden vortex-antivortex cluster rather than an ordinary giant vortex in each component. Of particular interest, when the strengths of DDI and quadrupole field are fixed, strong SOC leads to the formation of criss-crossed vortex string structure. For given SOC and quadrupole field, the system for strong DDI displays a sandwich-like structure, or a special delaminated structure with a prolate antivortex in the spin-up component. In addition, typical spin textures for the ground states of the system are analyzed. It is shown that the system sustains exotic topological structures, such as a hyperbolic spin domain wall, skyrmion-half-antiskyrmion-antiskyrmion lattice, half-skyrmion-skyrmion-half-antiskyrmion lattice, and a drum-shaped antimeron.