Topological defects in spinor condensates

Mäkelä, Harri; Zhang, Yahong; Suominen, Kalle-Antti

doi:10.1088/0305-4470/36/32/302

Cited by 61 publications

(73 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They must instead reconnect by forming a rung vortex connecting the resulting defects. Non-Abelian defects have been proposed in BN liquid crystals [11] and theoretically classified in cyclic spin-2 BECs [13][14][15][16]48] and in certain spin-3 phases [17].…”

mentioning

confidence: 99%

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

Borgh

Ruostekoski

2016

Phys. Rev. Lett.

View full text Add to dashboard Cite

We calculate the energetic structure of defect cores and propose controlled methods to imprint a nontrivially entangled vortex pair that undergoes non-Abelian vortex reconnection in a biaxial nematic spin-2 condensate. For a singular vortex, we find three superfluid cores in addition to depletion of the condensate density. These exhibit order parameter symmetries that are different from the discrete symmetry of the biaxial nematic phase, forming an interface between the defect and the bulk superfluid. We provide a detailed analysis of phase mixing in the resulting vortex cores and find an instability dependent upon the orientation of the order parameter. We further show that the spin-2 condensate is a promising system for observing spontaneous deformation of a point defect into an "Alice ring" that has so far avoided experimental detection.Topological defects and textures are ubiquitous across physical systems that seemingly have little in common [1], from liquid crystals [2] and superfluids [3] to cosmic strings [4]. They arise generically from symmetries of a ground state that is described by an order parameter [5]-a function parametrizing the set of physically distinguishable, energetically degenerate states. In the simple example of a scalar superfluid, the order parameter is the phase of the macroscopic wave function. More generally it may be a vector or tensor that is symmetric under particular transformations. In a uniaxial nematic (UN), the order parameter is cylindrically symmetric around a locally defined axis. It also exhibits a twofold discrete symmetry under reversal of the cylinder axis, which leads to half-quantum vortices (HQVs) in atomic spinor BoseEinstein condensates (BECs) [6][7][8][9] and superfluid liquid 3 He [10], and to π disclinations in liquid crystals [1,2]. In a biaxial nematic (BN), also the cylindrical symmetry is broken into the fully discrete symmetry of a rectangular brick, with dramatic consequences: the BN is the simplest order parameter that supports non-Abelian vortices that do not commute [5,11]. As a result, colliding non-Abelian vortices cannot reconnect without leaving traces of the process, but must instead form a connecting rung vortex. Noncommuting defects appear as cosmic strings in theories of the early universe [4], and have been predicted in BN liquid crystals [11].Despite long-standing experimental efforts, BN phases in liquid crystals have experimentally proved more elusive than originally anticipated [12]. In atomic systems, the topological classification and dynamics of non-Abelian vortices have theoretically been studied in the cyclic phase of spin-2 [13-16] and in spin-3 BECs [17], though it remains uncertain whether any alkali-metal atoms exhibit the corresponding ground states. Consequently, any physical system where non-Abelian defects may be reliably studied is still lacking.Spin-2 BECs exhibit-in addition to the ferromagnetic (FM) and cyclic phases-both UN and BN phases [18][19][20], which, however, are degenerate at the mean-field level. Beyond mean-fi...

show abstract

mentioning

confidence: 99%

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

Borgh

Ruostekoski

2016

Phys. Rev. Lett.

View full text Add to dashboard Cite

show abstract

“…This system has brought up new paradigms. For example, many possibilities of the stationary vortex states arise in spinor BECs with F = 1, 2 [3,4,5,6]. The coreless vortex state, which we discuss in this paper, is the one of the interesting phenomena which cannot appear in the scalar BEC.…”

Section: Introductionmentioning

confidence: 91%

Dynamical stability of coreless vortex states inF= 1 spinor bose-einstein condensates

Takahashia

Pietilä

Möttönen³

et al. 2009

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

Abstract. We investigate the dynamical stability of the coreless vortex state in F = 1 spinor Bose-Einstein condensates, by numerically solving the Gross-Pitaevskii and Bogoliubovde Gennes equations. We cover both ferromagnetic and antiferromagnetic interaction regions and the magnetizations per particle M from −1 to +1. It is found that the coreless vortex state is dynamically stable in large parameter regions of magnetization M . At M = −1, the hyperfine spin component with vortex winding 2 is dominant, and hence the coreless vortex can spontaneously decay even without dissipation. However, it is found that in the ferromagnetic case, the spin-spin interactions tend to stabilize the state. In the antiferromagnetic case, we find new dynamical instability modes which are not obtained in the ferromagnetic interaction region. In the antiferromagnetic interaction region, the spin-spin interactions can stimulate dynamical instabilities, while there still remains a large stability area in the parameter M . This is because of certain restrictions in inducing dynamical instability.

show abstract

“…The global topology of the above ferromagnetic and polar order parameter manifolds naturally determines the character of the topological defects in the ordered phases, and certain features of the ordering transitions, some of which have already been discussed in the literature 15 . This is not the focus of the present work and topology will not be further discussed, even though the defect physics of the higher spin condensates promises to be highly non-trivial 16,17 . The polar state has φ † n,θ S (1) φ n,θ = 0.…”

Section: Identifying the Spin Degrees Of Freedommentioning

confidence: 99%

Low-energy dynamics of spinor condensates

Lamacraft

2010

Phys. Rev. B

View full text Add to dashboard Cite

We present a derivation of the low energy Lagrangian governing the dynamics of the spin degrees of freedom in a spinor Bose condensate, for any phase in which the average magnetization vanishes. This includes all phases found within mean-field treatments except for the ferromagnet, for which the low energy dynamics has been discussed previously. The Lagrangian takes the form of a sigma model for the rotation matrix describing the local orientation of the spin state of the gas.

show abstract

Topological defects in spinor condensates

Cited by 61 publications

References 14 publications

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

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

Dynamical stability of coreless vortex states inF= 1 spinor bose-einstein condensates

Low-energy dynamics of spinor condensates

Contact Info

Product

Resources

About