Skyrmionic vortex lattices in coherently coupled three-component Bose-Einstein condensates

TL;DR

This paper numerically demonstrates that three-component Bose-Einstein condensates with Rabi coupling can host complex vortex lattices, including square, zig-zag, and skyrmionic structures, due to the interplay of interactions and phase frustration.

Contribution

It introduces the concept of skyrmionic topological classification for vortex lattices in three-component BECs, revealing novel vortex physics at intermediate Rabi couplings.

Findings

Discovery of unconventional vortex lattices with complex patterns

Identification of skyrmionic topological index for classifying lattices

Observation of unique vortex phenomena at intermediate Rabi coupling

Abstract

We show numerically that a harmonically trapped and coherently Rabi-coupled three-component Bose-Einstein condensate can host unconventional vortex lattices in its rotating ground state. The discovered lattices incorporate square and zig-zag patterns, vortex dimers and chains, and doubly quantized vortices, and they can be quantitatively classified in terms of a skyrmionic topological index, which takes into account the multicomponent nature of the system. The exotic ground-state lattices arise due to the intricate interplay of the repulsive density-density interactions and the Rabi couplings as well as the ubiquitous phase frustration between the components. In the frustrated state, domain walls in the relative phases can persist between some components even at strong Rabi coupling, while vanishing between others. Consequently, in this limit the three-component condensate effectively approaches a two-component condensate with only density-density interactions. At intermediate Rabi coupling strengths, however, we face unique vortex physics that occurs neither in the two-component counterpart nor in the purely density-density-coupled three-component system.