Creation of topological states of a Bose-Einstein condensate in a plaquette

TL;DR

This paper investigates the formation of topological vortex states in a Bose-Einstein condensate confined in a square plaquette of microtraps, revealing how trap depth influences vortex localization and topological properties through dipolar interactions.

Contribution

It demonstrates the creation of topological vortex states in a BEC within a microtrap plaquette, highlighting the role of trap depth and symmetry in vortex structure formation.

Findings

Vortices appear in the initially empty $m_F=0$ state due to dipolar interactions.

Deep traps localize vortices at individual sites, shallow traps produce a single plaquette vortex.

Topological properties depend on the interplay between local axial and discrete symmetries.

Abstract

We study a square plaquette of four optical microtraps containing ultracold $^{87}$Rb atoms in F=1 hyperfine state. In a presence of external resonant magnetic field the dipolar interactions couple initial $m_F=1$ component to other Zeeman sublevels. This process is a generalization of the Einstein-de Haas effect to the case when the external potential has only $C_4$ point-symmetry. We observe that vortex structures appear in the initially empty $m_F=0$ state. Topological properties of this state are determined by competition between the local axial symmetry of the individual trap and the discrete symmetry of the plaquette. For deep microtraps vortices are localized at individual sites whereas for shallow traps only one discrete vortex appears in the plaquette. States created in these two opposite cases have different topological properties related to $C_4$ point-symmetry.