Stability and internal structure of vortices in spin-1 Bose-Einstein condensates with conserved magnetization

Abstract

We demonstrate how conservation of longitudinal magnetization can have pronounced effects on both stability and structure of vortices in the atomic spin-1 Bose-Einstein condensate by providing a systematic characterization of nonsingular and singular vortex states. Constructing spinor wave functions for vortex states that continuously connect ferromagnetic and polar phases, we systematically derive analytic models for nonrotating cores of different singular vortices and for composite defect states with distinct small-and large-distance topology. We explain how the conservation law provides a stabilizing mechanism when the coreless vortex imprinted on the condensate relaxes in the polar regime of interatomic interactions. The resulting structure forms a composite defect: The inner ferromagnetic coreless vortex deforms toward an outer singly quantized polar vortex. We also numerically show how other even more complex hierarchies of vortex-core topologies may be stabilized. Moreover, we analyze the structure of the coreless vortex also in a ferromagnetic condensate and show how reducing magnetization leads to a displacement of the vortex from the trap center and eventually to the deformation and splitting of its core where a singular vortex becomes a lower-energy state. For the case of singular vortices, we find that the stability and the core structure are notably less influenced by the conservation of magnetization.

Three-dimensional skyrmions in spin-2 Bose–Einstein condensates

“…Our additional numerical calculations show that both schemes result in identical skyrmionic structures. 9 Inelastic losses are not included in the Hamiltonian but are not expected to be important on the timescale of the skyrmion creation [53,54]. ) .…”

“…The experimental detection of quantized vortices has become routine in studies of superfluidity in gaseous BECs: the types of observed line defects in three dimensions include singly and multiply quantized vortices [9][10][11][12][13], coreless [14,15], polar-core [16], solitonic [17] and half-quantum vortices [18], and vortex lattices [19,20]. The interest in topological defects of dimensionality other than one has grown in recent years: the creation of two-dimensional skyrmions [15,21,22] was followed by the observation of point-like defects analogous to Dirac [23,24] and 'tHooft-Polyakov [25] monopoles.…”

Core Structure and Non-Abelian Reconnection of Defects in a Biaxial Nematic Spin-2 Bose-Einstein Condensate

“…Recent efforts in spin-1 BECs have led to the in situ observation of a singly quantized vortex splitting into a pair of HQVs [9], confirming theoretical prediction [8], and to controlled preparation of coreless-vortex textures [26][27][28], the analogs of Dirac [22] and 't Hooft-Polyakov [29] monopoles, and particlelike solitons [30]. Our results for spin-2 reveal a defect-structure phenomenology considerably richer than that in the spin-1 BECs [8,[31][32][33][34]. Preparation of spin-2 BECs has been achieved using 87 Rb [27,[35][36][37], which, like 23 Na, is predicted to exhibit the nematic phases [20,38].…”

Topological spinor vortex matter on spherical surface induced by non-Abelian spin-orbital-angular-momentum coupling

“…In the case of vanishing spin-exchange interaction, the defects of spin vortices can form stable lattice configurations on sphere characterized by the standard Thomson problem [50,69]. Meanwhile, in the polar regime with strong spin-exchange interaction, the system supports stable nontrivial polar states [67,70,71] characterized by Z 2 -type topological invariant. The system can be viewed as a vortex zoo of constructing stable spin vortices with novel intrinsic topology, and serve as a desired platform to explore various non-Abelian SOAM coupled physics for both bosons and fermions.…”