Boojums in Rotating Two-Component Bose–Einstein Condensates

Takeuchi, Hiromitsu; Tsubota, Makoto

doi:10.1143/jpsj.75.063601

Cited by 19 publications

(15 citation statements)

References 16 publications

(24 reference statements)

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“…Incorporating the immiscible regime Γ > 1 and the associated nonaxisymmetric stationary vortex states would present an opportunity to investigate the interplay [106] between vortex dynamics, phase separation [107][108][109], and instabilities associated with fluid interfaces [110][111][112]. Generalizing the study to threedimensional dynamics would enable us to study the splittinginduced intertwining of vortices [23,25,26] as well as the dynamics of composite defects consisting of vortex lines and interfaces [113][114][115]. It would also be interesting to study finite-temperature effects, given that the presence of the thermal component is predicted to stabilize an axisymmetric vortex energetically [116][117][118].…”

Section: Discussionmentioning

confidence: 99%

Splitting of singly and doubly quantized composite vortices in two-component Bose-Einstein condensates

et al. 2019

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We study numerically the dynamical instabilities and splitting of singly and doubly quantized composite vortices in nonrotated two-component Bose-Einstein condensates harmonically confined to quasi two dimensions. In this system, the vortices become pointlike composite defects that can be classified in terms of an integer pair (κ 1 ,κ 2 ) of phase-winding numbers. Our numerical simulations based on zero-temperature mean-field theory reveal several vortex splitting behaviors that stem from the multicomponent nature of the system and do not have direct counterparts in single-component condensates. By calculating the Bogoliubov quasiparticle excitations of stationary axisymmetric composite vortices, we find complex-frequency excitations (dynamical instabilities) for the singly quantized (1,1) and (1,−1) vortices and for all variants of doubly quantized vortices, which we define by max j=1,2 |κ j | = 2. While the predictions of the linear Bogoliubov analysis are confirmed by direct time integration of the Gross-Pitaevskii equations of motion, the latter also reveals intricate long-time decay behavior not captured by the linearized dynamics. Firstly, the (1,±1) vortex is found to be unstable against splitting into a (1,0) and a (0,±1) vortex. Secondly, the (2,1) vortex exhibits a two-step decay process by splitting first into a (2,0) and a (0,1) vortex followed by the off-axis splitting of the (2,0) vortex into two (1,0) vortices. Thirdly, the (2,−2) vortex is observed to split into a (−1,1) vortex, three (1,0) vortices, and three (0,−1) vortices. Each of these exotic splitting modes is the dominant dynamical instability of the respective stationary vortex in a wide range of intercomponent interaction strengths and relative populations of the two condensate components and should be amenable to experimental detection. Our results contribute to a better understanding of vortex physics, hydrodynamic instabilities, and two-dimensional quantum turbulence in multicomponent superfluids.The aforementioned studies of vortex splitting [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] were conducted for a solitary scalar BEC, which is described by a single C-valued order parameter. However, vortex physics becomes much more diverse when multiple, say K ∈ N, scalar condensates come into contact, interact with one another, and thereby constitute an K-component BEC described by a C K -valued vectorial order parameter. Already the simplest multicomponent system, the two-component BEC corresponding to K = 2, has been found to exhibit many stable vortex structures not encountered in single-component BECs, such as coreless vortices [6], square vortex lattices [47][48][49], serpentine vortex sheets [50], triangular lattices of vortex pairs [49], skyrmions [51][52][53], and meron pairs [54,55]. Although presently only the coreless vortices [6] and square vortex lattices [48] from this list have been verified experimentally, studies of exotic vortex configurations in twocomponent BECs are becoming more and more within reach ...

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Section: Discussionmentioning

confidence: 99%

Splitting of singly and doubly quantized composite vortices in two-component Bose-Einstein condensates

et al. 2019

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“…Higher-dimensional defects and textures include vortex sheets [44] and 3D particlelike solitons [20][21][22][45][46][47] in two-component (pseudospin-1/2) condensates, as well as a rich phenomenology of defects and textures in spin-1 [23,24,26,[48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63], spin-2 [64][65][66], and spin-3 [30,67] BECs. Interface physics has been studied in two-component BEC systems, for example, in the context of vortex bifurcation at energetically established interfaces in the phase-separation regime [68,69] and interface collisions [19]. There is a rapid parallel experimental development, exemplified by preparation of coreless vortices and related textures [70][71][72][73], as well as observations of singular vortices produced in phase transitions [74], and of spin-texture formation [75][76][77].…”

Section: Introductionmentioning

confidence: 99%

Topological interface physics of defects and textures in spinor Bose-Einstein condensates

Borgh

Ruostekoski

2013

Phys. Rev. A

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We provide a detailed description of our previously proposed scheme for topological interface engineering with constructed defects and textures perforating across coherent interfaces between different broken symmetries [Borgh and Ruostekoski, Phys. Rev. Lett. 109, 015302 (2012)]. We consider a spin-1 Bose-Einstein condensate, in which polar and ferromagnetic phases are prepared in spatially separated regions. We show that a stable coherent interface is established between the two phases, allowing defects of different topology to connect continuously across the boundary. We provide analytic constructions of interface-crossing defect solutions that could be experimentally phase imprinted using existing technology. By numerically minimizing the energy, we calculate the core structures of interface-crossing defect configurations. We demonstrate nontrivial core deformations to considerably more complex structures, such as the formation of an arch-shaped half-quantum line defect, an Alice arch, at the interface, with the topological charge of a point defect, whose emergence may be understood by the "hairy ball" theorem. Another example of an energetically stable object is the connection of a coreless vortex to a pair of half-quantum vortices. We show that rotation leads to spontaneous nucleation of defects in which a coreless vortex continuously transforms to a half-quantum vortex across the interface.

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“…This term and the concept of boojums quickly penetrated different fields of physics and materials science, ranging from liquid crystals (LCs) to Langmuir monolayers, and to Bose-Einstein condensates (3)(4)(5)(6). However, unlike in the case of their bulk topological counterparts (7)(8)(9)(10), called "hedgehog" point defects, the appearance of boojums is rarely controlled at will.…”

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confidence: 99%

Nematic liquid crystal boojums with handles on colloidal handlebodies

Liu¹,

Senyuk

Tasinkevych

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

111

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Topological defects that form on surfaces of ordered media, dubbed boojums, are ubiquitous in superfluids, liquid crystals (LCs), Langmuir monolayers, and Bose-Einstein condensates. They determine supercurrents in superfluids, impinge on electrooptical switching in polymerdispersed LCs, and mediate chemical response at nematic-isotropic fluid interfaces, but the role of surface topology in the appearance, stability, and core structure of these defects remains poorly understood. Here, we demonstrate robust generation of boojums by controlling surface topology of colloidal particles that impose tangential boundary conditions for the alignment of LC molecules. To do this, we design handlebody-shaped polymer particles with different genus g. When introduced into a nematic LC, these particles distort the nematic molecular alignment field while obeying topological constraints and induce at least 2g − 2 boojums that allow for topological charge conservation. We characterize 3D textures of boojums using polarized nonlinear optical imaging of molecular alignment and explain our findings by invoking symmetry considerations and numerical modeling of experiment-matching director fields, order parameter variations, and nontrivial handle-shaped core structure of defects. Finally, we discuss how this interplay between the topologies of colloidal surfaces and boojums may lead to controlled self-assembly of colloidal particles in nematic and paranematic hosts, which, in turn, may enable reconfigurable topological composites.eing inspired by Lewis Carroll's poem The Hunting of the Snark, Mermin (1, 2) introduced a term "boojum" to name elusive at the time surface defects in superfluids. This term and the concept of boojums quickly penetrated different fields of physics and materials science, ranging from liquid crystals (LCs) to Langmuir monolayers, and to Bose-Einstein condensates (3-6). However, unlike in the case of their bulk topological counterparts (7-10), called "hedgehog" point defects, the appearance of boojums is rarely controlled at will. In LCs, boojums can spontaneously appear at their interfaces with isotropic media, such as water. They are commonly associated with the geometries of thin LC films on surfaces of isotropic fluids (11), LC droplets (3, 4, 12), and colloidal inclusions (13,14). For example, spherical surfaces with tangential boundary conditions for rod-like LC molecules, and director n describing their local average orientation, are known to induce two boojums per LC droplet or per colloidal inclusion in the LC host (3,4,13,14). However, despite the recent progress in generating and controlling bulk LC defects using director realignment with focused laser beams, chirality, and surface topology of colloidal particles with perpendicular surface anchoring introduced into LCs (7-10), similar control of boojums has not been demonstrated.In this work, we fabricate polymer microparticles with the topology of a handlebody of genus g ranging from one to five that are capable of imposing tangentially degenerate s...

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Boojums in Rotating Two-Component Bose–Einstein Condensates

Cited by 19 publications

References 16 publications

Splitting of singly and doubly quantized composite vortices in two-component Bose-Einstein condensates

Splitting of singly and doubly quantized composite vortices in two-component Bose-Einstein condensates

Topological interface physics of defects and textures in spinor Bose-Einstein condensates

Nematic liquid crystal boojums with handles on colloidal handlebodies

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