Beyond the simple hexagonal Abrikosov vortex lattice in layered superconductors
NASA Astrophysics Data System (ADS)
Feinberg, D.; Ettouhami, A. M.
1993-01-01
In layered superconductors as high-Tc materials but also organic superconductors, chalcogenides and superlattices, the simple concept of an distorted hexagonal lattice of straight vortices becomes unsufficient. Due to anisotropy and short coherence lengths, quite new vortex structures may arise. Some of them, as staircase vortices, simply add a modulation in the direction of vortex lines. This phenomenon is reviewed, together with the resulting lock-in transition, especially when the effects of the layered structure are weak. More exotic structures like a decomposed vortex lattice can also occur in specific situations: they involve two perpendicular sublattices, one parallel and one normal to the layers. We propose that extended defects as twin boundaries or irradiation tracks can trigger such a structure even in moderately anisotropic compounds as Y:123.
Hierarchy of gaps and magnetic minibands in graphene in the presence of the Abrikosov vortex lattice
NASA Astrophysics Data System (ADS)
Chen, Xi; Fal'ko, Vladimir I.
2016-01-01
We determine the bands and gaps in graphene subjected to the magnetic field of an Abrikosov lattice of vortices in the underlying superconducting film. The spectrum features one nondispersive magnetic miniband at zero energy, separated by the largest gaps in the miniband spectrum from a pair of minibands resembling a slightly broadened first Landau level in graphene, suggesting the persistence of ν =±2 and ±6 quantum Hall effect states. Also, we identify an occasional merging point of magnetic minibands with a Dirac-type dispersion at the miniband edges.
Haymaker, Richard W.; Matsuki, Takayuki
2007-01-01
We address the problem of determining the type I, type II or borderline dual superconductor behavior in maximal Abelian gauge SU(2) through the study of the dual Abrikosov vortex. We find that significant electric currents in the simulation data call into question the use of the dual Ginzburg-Landau Higgs model in interpreting the data. Further, two definitions of the penetration depth parameter take two different values. The splitting of this parameter into two is intricately connected to the existence of electric currents. It is important in our approach that we employ definitions of flux and electric and magnetic currents that respect Maxwell equations exactly for lattice averages independent of lattice spacings. Applied to specific Wilson loop sizes, our conclusions differ from those that use the dual GLH model.
Numerical calculations of the driving force on an Abrikosov vortex
NASA Astrophysics Data System (ADS)
Chen, D.-X.; Pardo, E.; Sanchez, A.
2010-05-01
The driving force on an Abrikosov vortex is calculated numerically from the London equation and involved energies for a vortex perpendicular to the screening current near the surface of a superconductor. Compared with previous analytical derivation of the total force, the partial magnetic, kinematic, and external forces are also obtained so that the nature of the driving force may be deeply discussed. It is shown that the force is neither a Lorentz force nor a Magnus force as often believed and that in order to get a correct result, the image effects and the work done by the applied field must be taken into account. A name of London force is suggested for the driving force. A deep understanding of the nature of the driving force on Abrikosov vortices may also be important in the study of vortex pinning and dynamics in type-II superconductors.
Melting of the Abrikosov flux lattice in anisotropic superconductors
NASA Technical Reports Server (NTRS)
Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.
1992-01-01
It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.
Dynamic Melting of Driven Abrikosov Lattices in an Amorphous MoxGe1-x Film in Tilted Field
NASA Astrophysics Data System (ADS)
Ochi, Aguri; Kawamura, Yasuki; Inoue, Toshiki; Kaji, Tetsuya; Mihaly, Dobroka; Kaneko, Shin-ichi; Kokubo, Nobuhito; Okuma, Satoshi
2016-03-01
We report a comparative study of the dynamic melting of driven vortex lattices in magnetic field tilted (by θ = 36°) from the normal to the film surface and that of a driven Abrikosov lattice in untilted field (θ = 0). From the mode-locking (ML) resonance, we confirm that vortex lattices in tilted field are stretched in the tilt direction and that, with increasing dc velocity at ML, the shape and orientation of the driven lattice change. Associated with this structural change, the dynamic melting field at which the driven lattice melts also changes. Our results show that, regardless of the lattice shape and orientation, dynamic melting occurs as the shorter side of the distorted lattices reaches close to the side at which the isotropic lattice melts dynamically.
Macroscopic evidence for Abrikosov-type magnetic vortexes in MnSi A-phase
Lobanova, I. I.; Glushkov, V. V.; Sluchanko, N. E.; Demishev, S. V.
2016-01-01
Intrinsic phase coherence between individual topologically stable knots in spin arrangement – skyrmions – is known to induce the crystalline-like structure in the A-phase of non-centrosymmetric MnSi with chiral spin-orbit interaction. Here we report the experimental evidence for two types of the skyrmion lattice (SL) inside the A-phase of MnSi, which are distinguished by different coupling to the anisotropic magnetic interactions. The transition between these SLs is shown to induce a change in magnetic scattering between isotropic MR discovered in the area inside the A-phase (the A-phase core) and anisotropic MR found on the border of the A-phase. We argue that the SL in the A-phase core corresponds to the dense skyrmion state built from individual skyrmions in a way similar to Abrikosov-type magnetic vortexes. PMID:26915818
Macroscopic evidence for Abrikosov-type magnetic vortexes in MnSi A-phase
NASA Astrophysics Data System (ADS)
Lobanova, I. I.; Glushkov, V. V.; Sluchanko, N. E.; Demishev, S. V.
2016-02-01
Intrinsic phase coherence between individual topologically stable knots in spin arrangement - skyrmions - is known to induce the crystalline-like structure in the A-phase of non-centrosymmetric MnSi with chiral spin-orbit interaction. Here we report the experimental evidence for two types of the skyrmion lattice (SL) inside the A-phase of MnSi, which are distinguished by different coupling to the anisotropic magnetic interactions. The transition between these SLs is shown to induce a change in magnetic scattering between isotropic MR discovered in the area inside the A-phase (the A-phase core) and anisotropic MR found on the border of the A-phase. We argue that the SL in the A-phase core corresponds to the dense skyrmion state built from individual skyrmions in a way similar to Abrikosov-type magnetic vortexes.
A single Abrikosov vortex trapped in a mesoscopic superconducting cylindrical surface
NASA Astrophysics Data System (ADS)
Carapella, G.; Sabatino, P.; Costabile, G.
2011-11-01
We investigate the behaviour of a single Abrikosov vortex trapped in a mesoscopic superconducting cylindrical surface with a magnetic field applied transverse to its axis. In the framework of the time-dependent Ginzburg-Landau formalism we show that, provided the transport current and the magnetic field are not large, the vortex behaves as an overdamped quasi-particle in a tilted washboard potential. The cylindrical thin strip with the trapped vortex exhibits E(J) curves and time-dependent electric fields very similar to the ones exhibited by a resistively shunted Josephson weak link.
Effect of fluctuations on the NMR relaxation beyond the Abrikosov vortex state
NASA Astrophysics Data System (ADS)
Glatz, A.; Galda, A.; Varlamov, A. A.
2015-08-01
The effect of fluctuations on the nuclear magnetic resonance (NMR) relaxation rate W =T1-1 is studied in a complete phase diagram of a two-dimensional superconductor above the upper critical field line Hc 2(T ) . In the region of relatively high temperatures and low magnetic fields, the relaxation rate W is determined by two competing effects. The first one is its decrease in the result of suppression of the quasiparticle density of states (DOS) due to formation of fluctuation Cooper pairs (FCPs). The second one is a specific, purely quantum relaxation process of the Maki-Thompson (MT) type, which for low field leads to an increase of the relaxation rate. The latter describes particular fluctuation processes involving self-pairing of a single electron on self-intersecting trajectories of a size up to phase-breaking length ℓϕ which becomes possible due to an electron spin-flip scattering event at a nucleus. As a result, different scenarios with either growth or decrease of the NMR relaxation rate are possible upon approaching the normal-metal-type-II superconductor transition. The character of fluctuations changes along the line Hc 2(T ) from the thermal long-wavelength type in weak magnetic fields to the clusters of rotating FCPs in fields comparable to Hc 2(0 ) . We find that below the well-defined temperature T0*≈0.6 Tc 0 , the MT process becomes ineffective even in the absence of intrinsic pair breaking. The small scale of the FCP rotations ξxy in such high fields impedes formation of long (≲ℓϕ) self-intersecting trajectories, causing the corresponding relaxation mechanism to lose its efficiency. This reduces the effect of superconducting fluctuations in the domain of high fields and low temperatures to just the suppression of quasiparticle DOS, analogous to the Abrikosov vortex phase below the Hc 2(T ) line.
Hall Effect in the Abrikosov Lattice of Type-II Superconductors
NASA Astrophysics Data System (ADS)
Kohno, Wataru; Ueki, Hikaru; Kita, Takafumi
2016-08-01
We study vortex charging caused by the Lorentz force on supercurrent based on the augmented quasiclassical equations of superconductivity. Our numerical study on an s-wave vortex lattice in the range Hc1 < H < Hc2 reveals that each vortex core with a single flux quantum also accumulates charge due to the circulating supercurrent and has a Hall voltage across the core. The field dependence of the charge density at the core center is well described by ρ(0) ∝ H(Hc2 - H) with a peak near Hc2/2 originating from competition between the increasing magnetic field and the decreasing pair potential. The peak value of the accumulated charge in a core region of radius 0.5ξ0 is estimated to be about ηΔ0/(kFξ0) × |e| C per Δz = 10 Å along the flux line at low temperatures, where η ≡ πɛ0Δz/|e|2 = 1.09 × 1018 J-1 with e < 0 the charge of an electron, Δ0 the energy gap at T = 0, kF the Fermi wave number, and ξ0 the coherence length at T = 0.
The structure of a moving vortex lattice
Braun, D.W.; Crabtree, G.W.; Kaper, H.G.; Leaf, G.K.; Levine, D.M.; Vinokur, V.M.; Koshelev, A.E.
1995-11-01
Numerical solutions of the time-dependent Ginzburg-Landau equations show a new mechanism for plastic motion of a driven vortex lattice in a clean superconductor. The mechanism, which involves the creation of a defect superstructure, is intrinsic to the moving vortex lattice and is independent of bulk pinning. Other structural features found in the solutions include a reorientation of the vortex lattice and a gradual healing of lattice defects under the influence of a transport current.
Vortex lattice of surface plasmon polaritons
NASA Astrophysics Data System (ADS)
Dzedolik, Igor V.; Lapayeva, Svetlana; Pereskokov, Vladislav
2016-07-01
We theoretically investigate the formation of a plasmon polariton vortex lattice on a metal surface following the interference of surface plasmon polaritons (SPPs). The plasmon polariton vortex lattice is formed by the interference of the SPP transverse-magnetic mode (TM-mode) and electric mode (E-mode) in the presence of the inhomogeneity with a curvilinear boundary on the surface of the metal layer. The SPP vortex lattice can be controlled by changing the configuration of the boundary. Weak nonlinearity of the metal permittivity does not change the interference pattern, but it increases the propagation length of the SPPs and, therefore, the area of the vortex lattice too.
Perturbed vortex lattices and the stability of nucleated topological phases
NASA Astrophysics Data System (ADS)
Lahtinen, Ville; Ludwig, Andreas W. W.; Trebst, Simon
2014-02-01
We study the stability of nucleated topological phases that can emerge when interacting non-Abelian anyons form a regular array. The studies are carried out in the context of Kitaev's honeycomb model, where we consider three distinct types of perturbations in the presence of a lattice of Majorana mode binding vortices—spatial anisotropy of the vortices, dimerization of the vortex lattice, and local random disorder. While all the nucleated phases are stable with respect to weak perturbations of each kind, strong perturbations are found to result in very different behavior. Anisotropy of the vortices stabilizes the strong-pairing-like phases, while dimerization can recover the underlying non-Abelian phase. Local random disorder, on the other hand, can drive all the nucleated phases into a gapless thermal metal state. We show that all these distinct behaviors can be captured by an effective staggered tight-binding model for the Majorana modes. By studying the pairwise interactions between the vortices, i.e., the amplitudes for the Majorana modes to tunnel between vortex cores, the locations of phase transitions and the nature of the resulting states can be predicted. We also find that, due to oscillations in the Majorana tunneling amplitude, lattices of Majorana modes may exhibit a Peierls-like instability, where a dimerized configuration is favored over a uniform lattice. As the nature of the nucleated phases depends only on the Majorana tunneling, our results are expected to apply also to other system supporting localized Majorana mode arrays, such as Abrikosov lattices in p-wave superconductors, Wigner crystals in Moore-Read fractional quantum Hall states, or arrays of topological nanowires.
Josephson vortex lattice in layered superconductors
Koshelev, A. E.; Dodgson, M. J. W.
2013-09-15
Many superconducting materials are composed of weakly coupled conducting layers. Such a layered structure has a very strong influence on the properties of vortex matter in a magnetic field. This review focuses on the properties of the Josephson vortex lattice generated by the magnetic field applied in the direction of the layers. The theoretical description is based on the Lawrence-Doniach model in the London limit, which takes only the phase degree of freedom of the superconducting order parameter into account. In spite of its simplicity, this model leads to an amazingly rich set of phenomena. We review in detail the structure of an isolated vortex line and various properties of the vortex lattice, in both dilute and dense limits. In particular, we extensively discuss the influence of the layered structure and thermal fluctuations on the selection of lattice configurations at different magnetic fields.
Vortex lattices in theory and practice
Capmbell, Laurence J.
1988-01-01
The formal simplicity of ideal point vortex systems in two dimensions has long attracted interest in both their exact solutions and in their capacity to simulate physical processes. Attention here is focused on infinite, two-fold periodic vortex arrays, including an expression for the energy density of an arbitrary vortex lattice (i.e., an arbitrary number of vortices with arbitrary strengths in a unit cell parallelogram of arbitrary shape). For the case of two vortices per unit cell, the morphology of stable lattices can be described completely. A non-trivial physical realization of such lattices is a rotating mixture of /sup 3/He and /sup 4/He at temperatures so low that both isotopic components are superfluid. The structure of the expected lattices is quite different from the usual triangular structure. Magnetic flux lines in high-temperature superconductors show a one-parameter family of degenerate ground state of the lattice due to the anisotropy of the vortex--vortex interaction. A final topic, closely related to Josephson-junction arrays, is the case of vortices confined to a grid. That is, the vortices interact pair-wise in the usual manner but are constrained to occupy only locations on an independent periodic grid. By using vortex relaxation methods in the continuum and then imposing the grid it is possible to find low-lying states extremely rapidly compared to previous Monte Carlo calculations. 11 refs., 8 figs.
Optical vortex array in spatially varying lattice
NASA Astrophysics Data System (ADS)
Kapoor, Amit; Kumar, Manish; Senthilkumaran, P.; Joseph, Joby
2016-04-01
We present an experimental method based on a modified multiple beam interference approach to generate an optical vortex array arranged in a spatially varying lattice. This method involves two steps which are: numerical synthesis of a consistent phase mask by using two-dimensional integrated phase gradient calculations and experimental implementation of produced phase mask by utilizing a phase only spatial light modulator in an optical 4f Fourier filtering setup. This method enables an independent variation of the orientation and period of the vortex lattice. As working examples, we provide the experimental demonstration of various spatially variant optical vortex lattices. We further confirm the existence of optical vortices by formation of fork fringes. Such lattices may find applications in size dependent trapping, sorting, manipulation and photonic crystals.
Energy of infinite vortex lattices
Campbell, L.J.; Doria, M.M.; Kadtke, J.B.
1989-05-15
An expression is derived for the energy density of a lattice of point vortices (or other logarithmic objects) having an arbitrary number of vortices of arbitrary strengths in an arbitrary unit cell. The result is expressed in the form of a rapidly convergent series well suited for numerical evaluation. The effects of separately changing the shape and dimensions of the unit cell are shown for simple cases, and the energy of the triangular lattice is calculated as a function of slip displacement.
Kouzoudis, D.
1999-02-12
The prime interest of the present research is to measure the thermal energy needed for depinning a trapped vortex when an external magnetic field is perpendicular to the plane of the junction, and thus there are Meissner currents flowing along the edge of the film. These currents introduce an additional force and the author wishes to study thermal depinning under the influence of this force. These studies are of interest because Nb junctions are used in a wide range of electronic applications. Such junctions are useful, for instance, in superconducting quantum interference devices (SQUIDs) or in vortex-flow transistors because their performance can be enhanced by tuning the parameters of the individual junctions to optimum operation values. Furthermore gated Josephson junctions can be used as Josephson field-effect transistors (JOFETs).
Single Abrikosov vortices as quantized information bits
NASA Astrophysics Data System (ADS)
Golod, T.; Iovan, A.; Krasnov, V. M.
2015-10-01
Superconducting digital devices can be advantageously used in future supercomputers because they can greatly reduce the dissipation power and increase the speed of operation. Non-volatile quantized states are ideal for the realization of classical Boolean logics. A quantized Abrikosov vortex represents the most compact magnetic object in superconductors, which can be utilized for creation of high-density digital cryoelectronics. In this work we provide a proof of concept for Abrikosov-vortex-based random access memory cell, in which a single vortex is used as an information bit. We demonstrate high-endurance write operation and two different ways of read-out using a spin valve or a Josephson junction. These memory cells are characterized by an infinite magnetoresistance between 0 and 1 states, a short access time, a scalability to nm sizes and an extremely low write energy. Non-volatility and perfect reproducibility are inherent for such a device due to the quantized nature of the vortex.
Reconstruction of vortex lattices at low inductions
Sudbro, A.; Brandt, E.H. Max-Planck-Institut fuer Metallforschung, Institut fuer Physik, Heisenbergstrasse 1, D-7000 Stuttgart 80 )
1992-03-16
The nonlocal elasticity and the normal modes of an unpinned flux-line lattice (FLL) in a uniaxially anisotropic supeconductor are considered in the low-induction regime {ital b}={ital B}/{ital B}{sub {ital c}2}{much lt}1 at oblique angles {theta} between {bold B} and the {bold {cflx c}} axis. A novel feature of anisotropic superconductors is {ital strongly} {ital dispersive} {ital shear} {ital moduli} when {theta}{gt}0. Thus, the normal modes of the FLL may become soft away from the zone center, signaling a {bold k}{ne}{bold 0} {ital structural} instability of the distorted hexagonal FLL. Vortex structures of a novel type are thus possible in anisotropic superconductors.
Simulating infinite vortex lattices in superfluids.
Mingarelli, Luca; Keaveny, Eric E; Barnett, Ryan
2016-07-20
We present an efficient framework to numerically treat infinite periodic vortex lattices in rotating superfluids described by the Gross-Pitaevskii theory. The commonly used split-step Fourier (SSF) spectral methods are inapplicable to such systems as the standard Fourier transform does not respect the boundary conditions mandated by the magnetic translation group. We present a generalisation of the SSF method which incorporates the correct boundary conditions by employing the so-called magnetic Fourier transform. We test the method and show that it reduces to known results in the lowest-Landau-level regime. While we focus on rotating scalar superfluids for simplicity, the framework can be naturally extended to treat multicomponent systems and systems under more general 'synthetic' gauge fields. PMID:27219843
Simulating infinite vortex lattices in superfluids
NASA Astrophysics Data System (ADS)
Mingarelli, Luca; Keaveny, Eric E.; Barnett, Ryan
2016-07-01
We present an efficient framework to numerically treat infinite periodic vortex lattices in rotating superfluids described by the Gross–Pitaevskii theory. The commonly used split-step Fourier (SSF) spectral methods are inapplicable to such systems as the standard Fourier transform does not respect the boundary conditions mandated by the magnetic translation group. We present a generalisation of the SSF method which incorporates the correct boundary conditions by employing the so-called magnetic Fourier transform. We test the method and show that it reduces to known results in the lowest-Landau-level regime. While we focus on rotating scalar superfluids for simplicity, the framework can be naturally extended to treat multicomponent systems and systems under more general ‘synthetic’ gauge fields.
Dynamic Reorganization of Vortex Matter into Partially Disordered Lattices.
Marziali Bermúdez, M; Eskildsen, M R; Bartkowiak, M; Nagy, G; Bekeris, V; Pasquini, G
2015-08-01
We report structural evidence of dynamic reorganization in vortex matter in clean NbSe(2) by joint small-angle neutron scattering and ac susceptibility measurements. The application of oscillatory forces in a transitional region near the order-disorder transition results in robust bulk vortex lattice configurations with an intermediate degree of disorder. These dynamically originated configurations correlate with intermediate pinning responses previously observed, resolving a long-standing debate regarding the origin of such responses. PMID:26296127
Vortex configurations of bosons in an optical lattice
Wu Congjun; Zhang Shoucheng; Chen Handong; Hu Jiangpiang
2004-04-01
The single-vortex problem in a strongly correlated bosonic system is investigated self-consistently within the mean-field theory of the Bose-Hubbard model. Near the superfluid-Mott-insulator transition, the vortex core has a tendency toward the Mott-insulating phase, with the core particle density approaching the nearest commensurate value. If the nearest-neighbor repulsion exists, the charge-density wave order may develop locally in the core. The evolution of the vortex configuration from the strong- to weak-coupling regions is studied. This phenomenon can be observed in systems of rotating ultracold atoms in optical lattices and Josephson-junction arrays.
Vortex-Antivortex Lattice in Ultracold Fermionic Gases
Botelho, S.S.; Melo, C.A.R. sa de
2006-02-03
We discuss ultracold Fermi gases in two dimensions, which could be realized in a strongly confining one-dimensional optical lattice. We obtain the temperature versus effective interaction phase diagram for an s-wave superfluid and show that, below a certain critical temperature T{sub c}, spontaneous vortex-antivortex pairs appear for all coupling strengths. In addition, we show that the evolution from weak-to-strong coupling is smooth, and that the system forms a square vortex-antivortex lattice at a lower critical temperature T{sub M}.
Quantum fluctuations of vortex lattices in ultracold gases
NASA Astrophysics Data System (ADS)
Kwasigroch, M. P.; Cooper, N. R.
2012-12-01
We discuss the effects of quantum fluctuations on the properties of vortex lattices in rapidly rotating ultracold atomic gases. We develop a variational method that goes beyond the Bogoliubov theory by including the effects of interactions between the quasiparticle excitations. These interactions are found to have significant quantitative effects on physical properties even at relatively large filling factors. We use our theory to predict the expected experimental signatures of quantum fluctuations of vortices and to assess the competition of the triangular vortex lattice phase with other phases in finite-sized systems.
Fluctuating pancake vortices revealed by dissipation of Josephson vortex lattice.
Koshelev, A. E.; Buzdin, A. I.; Kakeya, I.; Yamamoto, T.; Kadowaki, K.
2011-06-01
In strongly anisotropic layered superconductors in tilted magnetic fields, the Josephson vortex lattice coexists with the lattice of pancake vortices. Due to the interaction between them, the dissipation of the Josephson vortex lattice is very sensitive to the presence of the pancake vortices. If the c-axis magnetic field is smaller than the corresponding lower critical field, the pancake stacks are not formed but the individual pancakes may exist in the fluctuational regime either near the surface in large-size samples or in the central region for small-size mesas. We calculate the contribution of such fluctuating pancake vortices to the c-axis conductivity of the Josephson vortex lattice and compare the theoretical results with measurements on small mesas fabricated out of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} crystals. A fingerprint of fluctuating pancakes is a characteristic exponential dependence of the c-axis conductivity observed experimentally. Our results provide strong evidence of the existence of the fluctuating pancakes and their influence on the Josephson vortex lattice dissipation.
Persistence of Metastable Vortex Lattice Domains in MgB2 in the Presence of Vortex Motion
Rastovski, Catherine; Schlesinger, Kimberly; Gannon, William J; Dewhurst, Charles; Debeer-Schmitt, Lisa M; Zhigadlo, Nikolai; Karpinski, Janusz; Eskildsen, Morten
2013-01-01
Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.
Vortex-Lattice Utilization. [in aeronautical engineering and aircraft design
NASA Technical Reports Server (NTRS)
1976-01-01
The many novel, innovative, and unique implementations and applications of the vortex-lattice method to aerodynamic design and analysis which have been performed by Industry, Government, and Universities were presented. Although this analytical tool is not new, it continues to be utilized and refined in the aeronautical community.
Single Abrikosov vortices as quantized information bits
Golod, T.; Iovan, A.; Krasnov, V. M.
2015-01-01
Superconducting digital devices can be advantageously used in future supercomputers because they can greatly reduce the dissipation power and increase the speed of operation. Non-volatile quantized states are ideal for the realization of classical Boolean logics. A quantized Abrikosov vortex represents the most compact magnetic object in superconductors, which can be utilized for creation of high-density digital cryoelectronics. In this work we provide a proof of concept for Abrikosov-vortex-based random access memory cell, in which a single vortex is used as an information bit. We demonstrate high-endurance write operation and two different ways of read-out using a spin valve or a Josephson junction. These memory cells are characterized by an infinite magnetoresistance between 0 and 1 states, a short access time, a scalability to nm sizes and an extremely low write energy. Non-volatility and perfect reproducibility are inherent for such a device due to the quantized nature of the vortex. PMID:26456592
The Vortex Lattice Method for the Rotor-Vortex Interaction Problem
NASA Technical Reports Server (NTRS)
Padakannaya, R.
1974-01-01
The rotor blade-vortex interaction problem and the resulting impulsive airloads which generate undesirable noise levels are discussed. A numerical lifting surface method to predict unsteady aerodynamic forces induced on a finite aspect ratio rectangular wing by a straight, free vortex placed at an arbitrary angle in a subsonic incompressible free stream is developed first. Using a rigid wake assumption, the wake vortices are assumed to move downsteam with the free steam velocity. Unsteady load distributions are obtained which compare favorably with the results of planar lifting surface theory. The vortex lattice method has been extended to a single bladed rotor operating at high advance ratios and encountering a free vortex from a fixed wing upstream of the rotor. The predicted unsteady load distributions on the model rotor blade are generally in agreement with the experimental results. This method has also been extended to full scale rotor flight cases in which vortex induced loads near the tip of a rotor blade were indicated. In both the model and the full scale rotor blade airload calculations a flat planar wake was assumed which is a good approximation at large advance ratios because the downwash is small in comparison to the free stream at large advance ratios. The large fluctuations in the measured airloads near the tip of the rotor blade on the advance side is predicted closely by the vortex lattice method.
Inverse Melting of Vortex Lattice in Layered Superconductors
NASA Astrophysics Data System (ADS)
Wu, W. J.; He, Y. W.; Zhao, Z. G.; Liu, M.; Yang, Y. H.
Using molecular dynamic simulations for the melting transition of a flux line lattice(FLL) with point disordered pinnings, thermal fluctuations and magnetic interactions between pancake vortices, we study the disorder-driven melting transition from a disentangled and ordered Bragg glass (BG) to an entangled amorphous vortex glass (VG) or a vortex liquid (VL) in the pinning strength-temperature phase diagram. A portion of the BG region is found to be sandwiched in between the VG phase at lower temperatures and VL phase at higher temperatures, exhibiting inverse melting behavior observed recently on BSCCO crystals.
Vortex penetration depth of organic superconductors: Evidence for vortex lattice melting
Tea, N.H.; Giannetta, R.W.; Salamon, M.B.; Williams, J.M.; Wang, H.H.; Geiser, U.
1997-07-01
The authors observe a crossover field H* in the temperature and magnetic field dependence of the rf vortex penetration depth in {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br for {rvec H}{sub dc}{parallel}{cflx b}-axis. They find that H* can be described quantitatively by the 3D Lindemann melting theory; thus, it corresponds to the melting of the vortex lattice in {kappa}-(ET){sub 2}Cu[N(CN){sub 2}]Br and lies very close to the irreversibility line. In the vortex-liquid state, they argue that the saturation of the vortex penetration depth in a magnetic field results from the finite size of the sample. The results do not have the scaling form predicted by the Coffey-Clem model in contrast to previous findings.
Quasiclassical analysis of vortex lattice states in Rashba noncentrosymmetric superconductors
NASA Astrophysics Data System (ADS)
Dan, Yuichiro; Ikeda, Ryusuke
2015-10-01
Vortex lattice states occurring in noncentrosymmetric superconductors with a spin-orbit coupling of Rashba type under a magnetic field parallel to the symmetry plane are examined by assuming the s -wave pairing case and in an approach combining the quasiclassical theory with the Landau level expansion of the superconducting order parameter. The resulting field-temperature phase diagrams include not only a discontinuous transition but a continuous crossover between different vortex lattice structures, and, further, a critical end point of a structural transition line is found at an intermediate field and a low temperature in the present approach. It is pointed out that the strange field dependence of the vortex lattice structure is a consequence of that of its anisotropy stemming from the Rashba spin-orbit coupling, and that the critical end point is related to the helical phase modulation peculiar to these materials in the ideal Pauli-limited case. Furthermore, calculation results on the local density of states detectable in STM experiments are also presented.
The nature of long range order in the vortex lattice of high {Tc} superconductors
Ryu, S.; Doniach, S.; Kapitulnik, A.
1994-12-31
Recent neutron data on the disappearance of long-range order in the vortex lattice of BSCCO at fields of order 1 kGauss is interpreted in terms of the results of a Monte Carlo simulation of the thermodynamics of the vortex lattice in a pure system. The authors show that the neutron data is consistent with a disorder-driven phase transition from a vortex crystal at low fields to a vortex glass at higher fields.
Dynamics of polarized vortex solitons in nonlocal media with Bessel optical lattices.
Zhang, Bingzhi; Chen, Zhifeng
2015-09-21
We investigate the formation of polarized vortex solitons in nonlocal media with Bessel optical lattices and show the various dynamics of these solitons. Particularly, the stable high-order polarized vortex solitons, which are not found in local media with Bessel optical lattices, are found in nonlocal media. It is found that the nonlocal nonlinearity plays an important role in the stability of these solitons which is similar to that of phase vortex solitons. However, we show that the dynamics of these polarized vortex solitons are quite different from the phase vortex solitons. PMID:26406632
Vortex formation of a Bose-Einstein condensate in a rotating deep optical lattice
Kato, Akira; Nakano, Yuki; Kasamatsu, Kenichi; Matsui, Tetsuo
2011-11-15
We study the dynamics of vortex nucleation and lattice formation in a Bose-Einstein condensate in a rotating square optical lattice by numerical simulations of the Gross-Pitaevskii equation. Different dynamical regimes of vortex nucleation are found, depending on the depth and period of the optical lattice. We make an extensive comparison with the experiments by R. A. Williams et al.[Phys. Rev. Lett. 104, 050404 (2010)], especially focusing on the issues of the critical rotation frequency for the first vortex nucleation and the vortex number as a function of rotation frequency.
Melting of Vortex Lattice in Bose-Einstein Condensate in Presence of Disorder
NASA Astrophysics Data System (ADS)
Dey, Bishwajyoti
We study the vortex lattice dynamics in Bose-Einstein condensate (BEC) in presence of single impurity as well as random impurities or disorder. The single impurity is modeled by a Gaussian function while disorder is introduced in the system by a uniform random potential. Such potentials can be created experimentally by lasers. We solve the time-dependent Gross-Pitaevskii equation in two-dimensions using split-step Crank-Nicolson method. We first show that a single vortex can be pinned by an impurity. We then show that even a single impurity can distort the vortex lattice. For sufficiently strong impurity potential, the vortex lattice gets pinned to the impurity. We also show that a new type of giant hole with hidden vortices inside it can be created in the vortex lattice by a cluster of impurities. In presence of random impurity potential or disorder, the vortices get pinned at random positions leading to melting of the vortex lattice. We further show that the vortex lattice melting can also be induced by the pseudorandom potential generated by the superposition of two optical lattices. The absence of long-range order in the melted vortex lattice is demonstrated from the structure factor profile and the histogram of the distance between each pair of vortices. I would like to thank DST, India and BCUD SPPU, for financial assisance through research grants.
Transverse forces on a vortex in lattice models of superfluids
NASA Astrophysics Data System (ADS)
Sonin, E. B.
2013-12-01
The paper derives the transverse forces (the Magnus and the Lorentz forces) in the lattice models of superfluids in the continuous approximation. The continuous approximation restores translational invariance absent in the original lattice model, but the theory is not Galilean invariant. As a result, calculation of the two transverse forces on the vortex, Magnus force and Lorentz force, requires the analysis of two balances, for the true momentum of particles in the lattice (Magnus force) and for the quasimomentum (Lorentz force) known from the Bloch theory of particles in the periodic potential. While the developed theory yields the same Lorentz force, which was well known before, a new general expression for the Magnus force was obtained. The theory demonstrates how a small Magnus force emerges in the Josephson-junction array if the particle-hole symmetry is broken. The continuous approximation for the Bose-Hubbard model close to the superfluid-insulator transition was developed, which was used for calculation of the Magnus force. The theory shows that there is an area in the phase diagram for the Bose-Hubbard model, where the Magnus force has an inverse sign with respect to that which is expected from the sign of velocity circulation.
Vortex lattice phases in bosonic ladders in the presence of gauge field
NASA Astrophysics Data System (ADS)
Piraud, Marie; Greschner, Sebastian; Kolley, Fabian; McCulloch, Ian P.; Schollwoeck, Ulrich; Heidrich-Meisner, Fabian; Vekua, Temo
2016-05-01
We study vortex lattices in the interacting Bose-Hubbard model defined on two- and three-leg ladder geometries in the presence of a homogeneous flux. Our work is motivated by recent experiments using laser assisted-tunneling in optical lattices and lattices in synthetic dimensions, which studied the regime of weak interactions. We focus on the effects arising from stronger interactions, in both the real space optical lattice and the synthetic dimension schemes. Based on extensive density matrix renormalization group simulations and a bosonization analysis, we show that vortex lattices form at certain commensurate vortex densities. We identify the parameter space in which they emerge, and study their properties. Very interestingly, an enlarged unit cell forms in the vortex lattice phases, which can lead to the reversal of the current circulation-direction in both geometries. We demonstrate this effect in weak coupling and at sufficiently low temperature, and show that it is significant for intermediate interactions.
Vortex lattices in strongly interacting Fermi gas with crossed-beam dipole trap
NASA Astrophysics Data System (ADS)
Wu, Yuping; Yao, Xingcan; Chen, Haoze; Liu, Xiangpei; Wang, Xiaoqiong
2016-05-01
We have built an experiment system to explore the dynamic and vortex in quantum degenerate Li6 gas. By using UV MOT and crossed-beam dipole trap, we obtained BEC of 2* 105 molecules. With a tightly focused 532nm laser beam as rotating bucket wall, We observed vortex formation in strongly interacting fermi superfluid. At suitable stirring frequency we produced the condensate of fermi pairs for which up to 10 vortices were simultaneously present. We produced vortex lattices in different magnetic fields (from BEC side to BCS side). Also we measured the lifetime of vortex lattices in different interaction region. This work was funded by CAS and USTC.
Observation of Vortex Nucleation in a Rotating Two-Dimensional Lattice of Bose-Einstein Condensates
Williams, R. A.; Al-Assam, S.; Foot, C. J.
2010-02-05
We report the observation of vortex nucleation in a rotating optical lattice. A {sup 87}Rb Bose-Einstein condensate was loaded into a static two-dimensional lattice and the rotation frequency of the lattice was then increased from zero. We studied how vortex nucleation depended on optical lattice depth and rotation frequency. For deep lattices above the chemical potential of the condensate we observed a linear dependence of the number of vortices created with the rotation frequency, even below the thermodynamic critical frequency required for vortex nucleation. At these lattice depths the system formed an array of Josephson-coupled condensates. The effective magnetic field produced by rotation introduced characteristic relative phases between neighboring condensates, such that vortices were observed upon ramping down the lattice depth and recombining the condensates.
Ferromagnetic and antiferromagnetic order in bacterial vortex lattices
Wioland, Hugo; Woodhouse, Francis G.; Dunkel, Jörn; Goldstein, Raymond E.
2016-01-01
Despite their inherent non-equilibrium nature1, living systems can self-organize in highly ordered collective states2,3 that share striking similarities with the thermodynamic equilibrium phases4,5 of conventional condensed matter and fluid systems. Examples range from the liquid-crystal-like arrangements of bacterial colonies6,7, microbial suspensions8,9 and tissues10 to the coherent macro-scale dynamics in schools of fish11 and flocks of birds12. Yet, the generic mathematical principles that govern the emergence of structure in such artificial13 and biological6–9,14 systems are elusive. It is not clear when, or even whether, well-established theoretical concepts describing universal thermostatistics of equilibrium systems can capture and classify ordered states of living matter. Here, we connect these two previously disparate regimes: Through microfluidic experiments and mathematical modelling, we demonstrate that lattices of hydrodynamically coupled bacterial vortices can spontaneously organize into distinct phases of ferro- and antiferromagnetic order. The preferred phase can be controlled by tuning the vortex coupling through changes of the inter-cavity gap widths. The emergence of opposing order regimes is tightly linked to the existence of geometry-induced edge currents15,16, reminiscent of those in quantum systems17–19. Our experimental observations can be rationalized in terms of a generic lattice field theory, suggesting that bacterial spin networks belong to the same universality class as a wide range of equilibrium systems. PMID:27213004
Crossover from crossing to tilted vortex phase in Bi2Sr2CaCu2O8+δ single crystals near ab-plane
NASA Astrophysics Data System (ADS)
Mirkovic, Jovan; Buzdin, Alexandre; Kashiwagi, Takanari; Yamamoto, Takashi; Kadowaki, Kazuo
2013-01-01
In extremely anisotropic layered superconductors of Bi2Sr2CaCu2O8+δ the stacks of vortex pancakes (PV) and the Josephson vortex (JV) interpenetrate, and due to PV-JV mutual pinning energy, weakly interact and form various tilted and crossing lattice structures including vortex chains, stripes, mixed chain + lattice phases, etc. In order to study these phenomena, it is decisive to have excellent quality of samples and the ideal experimental techniques. The vortex phases in high-quality Bi2Sr2CaCu2O8+δ single crystals were studied by in-plane resistivity measurement and local ac magnetic permeability. The sharp crossover was shown by both techniques, deep in the vortex solid state separating the Abrikosov dominant ‘strong pinning’ phase from the Josephson dominant ‘weak pinning’ phase. Those two vortex states were recognized as the mixed chain + lattice vortex phase and chains (tilted) vortex phase, respectively.
Entanglement of Vortex Lattices for Ultracold Bose Gases in a Non-Abelian Gauge Potential
NASA Astrophysics Data System (ADS)
Cheng, Szu-Cheng; Jiang, T. F.; Jheng, Shih-Da; Atomic; Molecular Physics Team; Atomic; Molecular Physics Team
We develop a theory, referred to as the von Neumann lattice in a higher Landau level, for vortex lattices labelled by an integral number of flux quantums per unit cell in a higher Landau level. Using this lattice theory, we study the vortex lattice states of a pseudospin-1/2 ultracold Bose gas with contact interactions in a non-Abelian gauge potential. In addition to a uniform magnetic field, the Bose gas is also subjected to a non-Abelian gauge field, which creates an effect of the spin-orbit coupling to lift the spin degeneracy of the Landau levels. Because of interactions from the spin-orbit coupling, there are new degenerate points of the single particle spectrum due to the crossings of two Landau levels at certain coupling strengths. We show that interactions from the spin-orbit coupling force the nature and structure of the vortex lattice changing dramatically if the strength of the non-Abelian gauge field is increasing. We also find that the ground state of the vortex lattice at a degenerate point exhibits strong correlation and entanglement involving vortex lattices from different Landau levels. This entangled state builds the connection between two phases of vortex lattices during the first order phase transition of the adiabatic evolution.
Observation of the vortex lattice melting by NMR spin-lattice relaxation in the mixed state
Bulaevskii, L.N.; Hammel, P.C.; Vinokur, V.M.
1994-01-01
For anisotropic layered superconductors the effect of moving vortices on the nuclear spin magnetization is calculated. Current is supposed to flow along layers, and applied magnetic field is tilted with respect to c-axis. In the solid phase the motion of the vortex lattice produces an alternating magnetic field perpendicular to the applied field which causes the decay of the spin-echo amplitude. This decay rate will display an array of peaks as a function of frequency. In the liquid phase this alternating field contribute to the longitudinal relaxation rate W{sub 1} which has a single peak.
Vortex lattices generated by the Kelvin-Helmholtz instability in the Gross-Pitaevskii equation
Ohta, A.; Kashiwa, R.; Sakaguchi, H.
2010-11-15
Vortex streets are formed from sheared initial conditions in classical fluids even without viscosity, which is called the Kelvin-Helmholtz instability. We demonstrate that similar vortex streets are generated from sheared initial conditions by the direct numerical simulation of the Gross-Pitaevskii (GP) equation which describes the dynamics of the Bose-Einstein condensates. Furthermore, we show the vortex-lattice formation from sheared initial conditions analogous to the rigid-body rotation in the GP equation under a rotating harmonic potential. The vortex-lattice formation by the dynamical instability in the system without energy dissipation differs from the vortex-lattice formation process by the imaginary time evolution of the GP equation where the lowest energy state is obtained.
An interferometric patchwork to generate high-order quasi-nondiffracting vortex lattices
NASA Astrophysics Data System (ADS)
Li, Zhenhua; Liu, Hanping; Liu, Huilan; Xu, Shicai; Ma, Li; Cheng, Chuanfu; Wang, Li; Mingzhen, Li
2016-06-01
We propose an novel kind of interferometer to generate various quasinondiffracting vortex lattices with high topological charges. The wave vectors of the interfering beams distribute spatial-symmetrically on the surface patchwork of two concentric cones of different opening angles, and their transverse components site at the vertices of two mutual-inscribed common regular polygons. With certain beam number and particular initial phase distribution at the beams, novel vortex lattices such as Kagome type lattice with unusual vortex distribution are obtained. We further extend such interferometric scheme to multipoint interferometers for easier experimental realization, where the generated vortex lattices lose nondiffracting property. Such interferometric method have potential applications in fields such as direct nanostructure writings and multichannel optical manipulations.
NASA Astrophysics Data System (ADS)
Ganguli, Somesh Chandra; Singh, Harkirat; Ganguly, Rini; Bagwe, Vivas; Thamizhavel, Arumugam; Raychaudhuri, Pratap
2016-04-01
We report experimental evidence of strong orientational coupling between the crystal lattice and the vortex lattice in a weakly pinned Co-doped NbSe2 single crystal through direct imaging using low temperature scanning tunneling microscopy/spectroscopy. When the magnetic field is applied along the six-fold symmetric c-axis of the NbSe2 crystal, the basis vectors of the vortex lattice are preferentially aligned along the basis vectors of the crystal lattice. The orientational coupling between the vortex lattice and crystal lattice becomes more pronounced as the magnetic field is increased. This orientational coupling enhances the stability of the orientational order of the vortex lattice, which persists even in the disordered state at high fields where dislocations and disclinations have destroyed the topological order. Our results underpin the importance of crystal lattice symmetry on the vortex state phase diagram of weakly pinned type II superconductors.
Formation flying benefits based on vortex lattice calculations
NASA Technical Reports Server (NTRS)
Maskew, B.
1977-01-01
A quadrilateral vortex-lattice method was applied to a formation of three wings to calculate force and moment data for use in estimating potential benefits of flying aircraft in formation on extended range missions, and of anticipating the control problems which may exist. The investigation led to two types of formation having virtually the same overall benefits for the formation as a whole, i.e., a V or echelon formation and a double row formation (with two staggered rows of aircraft). These formations have unequal savings on aircraft within the formation, but this allows large longitudinal spacings between aircraft which is preferable to the small spacing required in formations having equal benefits for all aircraft. A reasonable trade-off between a practical formation size and range benefit seems to lie at about three to five aircraft with corresponding maximum potential range increases of about 46 percent to 67 percent. At this time it is not known what fraction of this potential range increase is achievable in practice.
Vortex-lattice melting in magnesium diboride in terms of the elastic theory
NASA Astrophysics Data System (ADS)
Nie, Qing-Miao; Lv, Jian-Ping; Chen, Qing-Hu
2010-01-01
In the framework of elastic theory, we study the vortex-lattice melting transitions in magnesium diboride for magnetic fields both parallel and perpendicular to the anisotropy axis. Using the parameters from experiments, the vortex-lattice melting lines in the H- T diagram are located systematically by various groups of Lindemann numbers. It is observed that the theoretical result for the vortex melting with parallel and perpendicular fields agrees well with the experimental data. Therefore, it is suggested that the phenomenological elastic theory is universal to various type-II superconductors, including two- and multi-band superconductors.
Application of lattice Boltzmann method for analysis of underwater vortex dynamics
NASA Astrophysics Data System (ADS)
Nuraiman, Dian; Viridi, Sparisoma; Purqon, Acep
2015-09-01
Vortex dynamics is one of problems arising in fluid dynamics. Vortices are a major characteristic of turbulent flow. We perform the Lattice Boltzmann Method (LBM) with Bhatnagar-Gross-Krook (BGK) approximation to analyze the underwater vortex dynamics close to the shoreline. Additionally, the Smagorinsky tubulence model is applied to treat turbulent flow and a special method for free surface treatment is applied to overcome free surface. Furthermore, we investigate the effect of the turbulence factor and the seabed profile to vortex dynamics. The results show a smaller turbulence factor affected to more turbulent flow and coral reefs reduced movement of vortex towards the shoreline.
Critical frequency for vortex nucleation in Bose-Fermi mixtures in optical lattices
NASA Astrophysics Data System (ADS)
Guilleumas, M.; Centelles, M.; Barranco, M.; Mayol, R.; Pi, M.
2005-11-01
We investigate within mean-field theory the influence of a one-dimensional optical lattice and of trapped degenerate fermions on the critical rotational frequency for vortex line creation in a Bose-Einstein condensate. We consider laser intensities of the lattice such that quantum coherence across the condensate is ensured. We find a sizable decrease of the thermodynamic critical frequency for vortex nucleation with increasing applied laser strength and suggest suitable parameters for experimental observation. Since Rb87-K40 mixtures may undergo collapse, we analyze the related question of how the optical lattice affects the mechanical stability of the system.
NASA Astrophysics Data System (ADS)
Sakaguchi, Hidetsugu; Umeda, Kanji
2016-06-01
The Gross-Pitaevskii equation for two-component rotating Bose-Einstein condensates with the Rashba-type spin-orbit (SO) coupling is studied with numerical simulations and variational analyses. A multiquantum vortex state becomes a ground state in a harmonic potential when mutual interaction is absent. When the attractive interaction is strong, the multiquantum vortex state exhibits modulational instability in the azimuthal direction, and a soliton-like state appears. When the repulsive interaction is strong, a vortex lattice state with a multiquantum vortex at the center is created. We find that the vortex lattice state is approximated at a linear combination of multiquantum vortex states.
NASA Technical Reports Server (NTRS)
Lamar, J. E.
1976-01-01
A new subsonic method has been developed by which the mean camber surface can be determined for trimmed noncoplanar planforms with minimum vortex drag. This method uses a vortex lattice and overcomes previous difficulties with chord loading specification. A Trefftz plane analysis is utilized to determine the optimum span loading for minimum drag, then solved for the mean camber surface of the wing, which provides the required loading. Sensitivity studies, comparisons with other theories, and applications to configurations which include a tandem wing and a wing winglet combination have been made and are presented.
A generalized vortex lattice method for subsonic and supersonic flow applications
NASA Technical Reports Server (NTRS)
Miranda, L. R.; Elliot, R. D.; Baker, W. M.
1977-01-01
If the discrete vortex lattice is considered as an approximation to the surface-distributed vorticity, then the concept of the generalized principal part of an integral yields a residual term to the vorticity-induced velocity field. The proper incorporation of this term to the velocity field generated by the discrete vortex lines renders the present vortex lattice method valid for supersonic flow. Special techniques for simulating nonzero thickness lifting surfaces and fusiform bodies with vortex lattice elements are included. Thickness effects of wing-like components are simulated by a double (biplanar) vortex lattice layer, and fusiform bodies are represented by a vortex grid arranged on a series of concentrical cylindrical surfaces. The analysis of sideslip effects by the subject method is described. Numerical considerations peculiar to the application of these techniques are also discussed. The method has been implemented in a digital computer code. A users manual is included along with a complete FORTRAN compilation, an executed case, and conversion programs for transforming input for the NASA wave drag program.
Abrikosov Gluon Vortices in Color Superconductors
NASA Astrophysics Data System (ADS)
Ferrer, Efrain J.
2011-09-01
In this talk I will discuss how the in-medium magnetic field can influence the gluon dynamics in a three-flavor color superconductor. It will be shown how at field strengths comparable to the charged gluon Meissner mass a new phase can be realized, giving rise to Abrikosov's vortices of charged gluons. In that phase, the inhomogeneous gluon condensate anti-screens the magnetic field due to the anomalous magnetic moment of these spin-1 particles. This paramagnetic effect can be of interest for astrophysics, since due to the gluon vortex antiscreening mechanism, compact stars with color superconducting cores could have larger magnetic fields than neutron stars made up entirely of nuclear matter. I will also discuss a second gluon condensation phenomenon connected to the Meissner instability attained at moderate densities by two-flavor color superconductors. In this situation, an inhomogeneous condensate of charged gluons emerges to remove the chromomagnetic instability created by the pairing mismatch, and as a consequence, the charged gluonic currents induce a magnetic field. Finally, I will point out a possible relation between glitches in neutron stars and the existence of the gluon vortices.
System Identification of a Vortex Lattice Aerodynamic Model
NASA Technical Reports Server (NTRS)
Juang, Jer-Nan; Kholodar, Denis; Dowell, Earl H.
2001-01-01
The state-space presentation of an aerodynamic vortex model is considered from a classical and system identification perspective. Using an aerodynamic vortex model as a numerical simulator of a wing tunnel experiment, both full state and limited state data or measurements are considered. Two possible approaches for system identification are presented and modal controllability and observability are also considered. The theory then is applied to the system identification of a flow over an aerodynamic delta wing and typical results are presented.
Formation of Vortex Lattices in Superfluid Bose Gases at Finite Temperatures
NASA Astrophysics Data System (ADS)
Arahata, E.; Nikuni, T.
2016-05-01
We study the dynamics of a rotating trapped Bose-Einstein condensate (BEC) at finite temperatures. Using the Zaremba-Nikuni-Griffin formalism, based on a generalized Gross-Pitaevskii equation for the condensate coupled to a semiclassical kinetic equation for a thermal cloud, we numerically simulate vortex lattice formation in the presence of a time-dependent rotating trap potential. At low rotation frequency, the thermal cloud undergoes rigid body rotation, while the condensate exhibits irrotational flow. Above a certain threshold rotation frequency, vortices penetrate into the condensate and form a vortex lattice. Our simulation result clearly indicates a crucial role for the thermal cloud, which triggers vortex lattice formation in the rotating BEC.
Quasi-Long-Range Order and Vortex Lattice in the Three-State Potts Model
NASA Astrophysics Data System (ADS)
Bhattacharya, Soumyadeep; Ray, Purusattam
2016-03-01
We show that the order-disorder phase transition in the three-state Potts ferromagnet on a square lattice is driven by a coupled proliferation of domain walls and vortices. Raising the vortex core energy above a threshold value decouples the proliferation and splits the transition into two. The phase between the two transitions exhibits an emergent U(1) symmetry and quasi-long-range order. Lowering the core energy below a threshold value also splits the order-disorder transition but the system forms a vortex lattice in the intermediate phase.
Imaging superconducting vortex cores and lattices with a scanning tunneling microscope
NASA Astrophysics Data System (ADS)
Suderow, H.; Guillamón, I.; Rodrigo, J. G.; Vieira, S.
2014-06-01
The observation of vortices in superconductors was a major breakthrough in developing the conceptual background for superconducting applications. Each vortex carries a flux quantum, and the magnetic field decreases radially from the center. Techniques used to make magnetic field maps, such as magnetic decoration, give vortex lattice images in a variety of systems. However, strong type II superconductors allow penetration of the magnetic field over large distances, of the order of the magnetic penetration depth λ. Superconductivity survives up to magnetic fields where, for imaging purposes, there is no magnetic contrast at all. Static and dynamic properties of vortices are largely unknown at such high magnetic fields. Reciprocal space studies using neutron scattering have been employed to obtain insight into the collective behavior. But the microscopic details of vortex arrangements and their motion remain difficult to obtain. Direct real-space visualization can be made using scanning tunneling microscopy and spectroscopy (STM/S). Instead of using magnetic contrast, the electronic density of states describes spatial variations of the quasiparticle and pair wavefunction properties. These are of the order of the superconducting coherence length ξ, which is much smaller than λ. In principle, individual vortices can be imaged using STM up to the upper critical field where vortex cores, of size ξ, overlap. In this review, we describe recent advances in vortex imaging made with scanning tunneling microscopy and spectroscopy. We introduce the technique and discuss vortex images that reveal the influence of the Fermi surface distribution of the superconducting gap on the internal structure of vortices, the collective behavior of the lattice in different materials and conditions, and the observation of vortex lattice melting. We consider challenging lines of work, which include imaging vortices in nanostructures, multiband and heavy fermion superconductors, single layers
Validation of Vortex-Lattice Method for loads on wings in lift-generated wakes
NASA Technical Reports Server (NTRS)
Rossow, J.
1994-01-01
A study is described that evaluates the accuracy of vortex-lattice methods when they are used to compute the loads induced on aircraft as they encounter lift-generated wakes. The evaluation is accomplished by use of measurements made in the 80- by 120-foot wind tunnel of the lift, rolling-moment, and downwash in the wake of three configurations of a model of a subsonic transport aircraft. The downwash measurements are used as input for a vortex-lattice code in order to compute the lift and rolling moment induced on wings that have a span of 0.186, 0.510, or 1.022 times the span of the wake-generating model. Comparison of the computed results with the measured lift and rolling moment distributions are used to determine the accuracy of the vortex-lattice code. It was found that the vortex-lattice method is very reliable as long as the span of the encountering of following wing is less than about 0.2 of the generator span. As the span of the following wing increases above 0.2, the vortex-lattice method continues to correctly predict the trends and nature of the induced loads, but it overpredicts the magnitude of the loads by increasing amounts. The increase in deviation of the computed from the measured loads with size of the following wing is attributed to the increase in distortion of the structure of the vortex wake as it approaches and passes the larger following wings.
Vortex lattices in a rotating Fermi superfluid in the BCS-BEC crossover with many Landau levels
Song, Tie-ling; Ma, C.R.; Ma, Yong-li
2012-08-15
We present an explicit analytical analysis of the ground state of vortex lattice structure, based on a minimization of the generalized Gross-Pitaevskii energy functional in a trapped rotating Fermi superfluid gas. By a Bogoliubov-like transformation we find that the coarse-grained average of the atomic density varies as inverted parabola in three dimensional cases; the Fermi superfluid in the BEC regime enters into the lowest Landau level at fast rotation, in which the vortices form an almost regular triangular lattice over a central region and the vortex lattice is expanded along the radial direction in the outer region; the fluid in the unitarity and BCS regimes occupies many low-lying Landau levels, in which a trapped gas with a triangular vortex lattice has a superfluid core surrounded by a normal gas. The calculation is qualitatively consistent with recent numerical and experimental data both in the vortex lattice structure and vortex numbers and in the density profiles versus the stirring frequency in the whole BCS-BEC crossover. - Highlights: Black-Right-Pointing-Pointer We present an analysis of vortex lattice in an interacting trapped rotating Fermi superfluid gas. Black-Right-Pointing-Pointer Decomposing the vortex from the condensate, we can explain the vortex lattice. Black-Right-Pointing-Pointer The calculation is consistent with numerical and experimental data. Black-Right-Pointing-Pointer It can characterize experimentally properties in different regimes of the BCS-BEC crossover.
Visualizing the morphology of vortex lattice domains in a bulk type-II superconductor.
Reimann, T; Mühlbauer, S; Schulz, M; Betz, B; Kaestner, A; Pipich, V; Böni, P; Grünzweig, C
2015-01-01
Alike materials in the solid state, the phase diagram of type-II superconductors exhibit crystalline, amorphous, liquid and spatially inhomogeneous phases. The multitude of different phases of vortex matter has thence proven to act as almost ideal model system for the study of both the underlying properties of superconductivity but also of general phenomena such as domain nucleation and morphology. Here we show how neutron grating interferometry yields detailed information on the vortex lattice and its domain structure in the intermediate mixed state of a type-II niobium superconductor. In particular, we identify the nucleation regions, how the intermediate mixed state expands, and where it finally evolves into the Shubnikov phase. Moreover, we complement the results obtained from neutron grating interferometry by small-angle neutron scattering that confirm the spatially resolved morphology found in the intermediate mixed state, and very small-angle neutron scattering that confirm the domain structure of the vortex lattice. PMID:26522610
Visualizing the morphology of vortex lattice domains in a bulk type-II superconductor
Reimann, T.; Mühlbauer, S.; Schulz, M.; Betz, B.; Kaestner, A.; Pipich, V.; Böni, P.; Grünzweig, C.
2015-01-01
Alike materials in the solid state, the phase diagram of type-II superconductors exhibit crystalline, amorphous, liquid and spatially inhomogeneous phases. The multitude of different phases of vortex matter has thence proven to act as almost ideal model system for the study of both the underlying properties of superconductivity but also of general phenomena such as domain nucleation and morphology. Here we show how neutron grating interferometry yields detailed information on the vortex lattice and its domain structure in the intermediate mixed state of a type-II niobium superconductor. In particular, we identify the nucleation regions, how the intermediate mixed state expands, and where it finally evolves into the Shubnikov phase. Moreover, we complement the results obtained from neutron grating interferometry by small-angle neutron scattering that confirm the spatially resolved morphology found in the intermediate mixed state, and very small-angle neutron scattering that confirm the domain structure of the vortex lattice. PMID:26522610
Validation of Vortex-Lattice Method for Loads on Wings in Lift-Generated Wakes
NASA Technical Reports Server (NTRS)
Rossow, Vernon J.
1995-01-01
A study is described that evaluates the accuracy of vortex-lattice methods when they are used to compute the loads induced on aircraft as they encounter lift-generated wakes. The evaluation is accomplished by the use of measurements made in the 80 by 120 ft Wind Tunnel of the lift, rolling moment, and downwash in the wake of three configurations of a model of a subsonic transport aircraft. The downwash measurements are used as input for a vortex-lattice code in order to compute the lift and rolling moment induced on wings that have a span of 0.186, 0.510, or 1.022 times the span of the wake-generating model. Comparison of the computed results with the measured lift and rolling-moment distributions the vortex-lattice method is very reliable as long as the span of the encountering or following wing is less than about 0.2 of the generator span. As the span of the following wing increases above 0.2, the vortex-lattice method continues to correctly predict the trends and nature of the induced loads, but it overpredicts the magnitude of the loads by increasing amounts.
Yao, Xiaoyan; Dong, Shuai
2016-01-01
The expanded classical Kitaev-Heisenberg model on a honeycomb lattice is investigated with the next-nearest-neighboring Heisenberg interaction considered. The simulation shows a rich phase diagram with periodic behavior in a wide parameter range. Beside the double 120° ordered phase, an inhomogeneous phase is uncovered to exhibit a topological triple-vortex lattice, corresponding to the hexagonal domain structure of vector chirality, which is stabilized by the mixed frustration of two sources: the geometrical frustration arising from the lattice structure as well as the frustration from the Kitaev couplings. PMID:27229486
NASA Astrophysics Data System (ADS)
Yao, Xiaoyan; Dong, Shuai
2016-05-01
The expanded classical Kitaev-Heisenberg model on a honeycomb lattice is investigated with the next-nearest-neighboring Heisenberg interaction considered. The simulation shows a rich phase diagram with periodic behavior in a wide parameter range. Beside the double 120° ordered phase, an inhomogeneous phase is uncovered to exhibit a topological triple-vortex lattice, corresponding to the hexagonal domain structure of vector chirality, which is stabilized by the mixed frustration of two sources: the geometrical frustration arising from the lattice structure as well as the frustration from the Kitaev couplings.
Z2-vortex lattice in the ground state of the triangular Kitaev-Heisenberg model
NASA Astrophysics Data System (ADS)
Daghofer, Maria; Rousochatzakis, Ioannis; Roessler, Ulrich K.; van den Brink, Jeroen
2013-03-01
Investigating the classical Kitaev-Heisenberg Hamiltonian on a triangular lattice, we establish the presence of an incommensurate non-coplanar magnetic phase, which is identified as a lattice of Z2 vortices. The vortices, topological point defects in the SO(3) order parameter of the nearby Heisenberg antiferromagnet, are not thermally excited but due to the spin-orbit coupling and arise at temperature T --> 0 . This Z2-vortex lattice is stable in a parameter regime relevant to iridates. We show that in the other, strongly anisotropic, limit a robust nematic phase emerges. Sponsored by the DFG (Emmy-Noether program).
Han, Qiang
2010-01-27
In this paper, we present a method to construct the eigenspace of the tight-binding electrons moving on a 2D square lattice with nearest-neighbor hopping in the presence of a perpendicular uniform magnetic field which imposes (quasi-)periodic boundary conditions for the wavefunctions in the magnetic unit cell. Exact unitary transformations are put forward to correlate the discrete eigenvectors of the 2D electrons with those of the Harper equation. The cyclic tridiagonal matrix associated with the Harper equation is then tridiagonalized by another unitary transformation. The obtained truncated eigenbasis is utilized to expand the Bogoliubov-de Gennes equations for the superconducting vortex lattice state, which shows the merit of our method in studying large-sized systems. To test our method, we have applied our results to study the vortex lattice state of an s-wave superconductor. PMID:21386295
NASA Astrophysics Data System (ADS)
Zhao, Qiang
2016-02-01
Motivated by recent experiments carried out by Spielman's group at NIST, we study the vortex formation in a rotating Bose-Einstein condensate in synthetic magnetic field confined in a harmonic potential combined with an optical lattice. We obtain numerical solutions of the two-dimensional Gross-Pitaevskii equation and compare the vortex formation by synthetic magnetic field method with those by rotating frame method. We conclude that a large angular momentum indeed can be created in the presence of the optical lattice. However, it is still more difficult to rotate the condensate by the synthetic magnetic field than by the rotating frame even if the optical lattice is added, and the chemical potential and energy remain almost unchanged by increasing rotational frequency.
Fractionalizing the vortex lattice in multiband superconductors in the flux flow region
NASA Astrophysics Data System (ADS)
Lin, Shi-Zeng
2014-03-01
Because of the discovery of MgB2 and iron-based superconductors, multiband superconductors have attracted considerable attention recently. Multiband superconductors are not always straightforward extensions of the single-band counterpart, and novel features may arise. In multiband superconductors, electrons in different bands form distinct superfluid condensates, which are coupled to the same gauge field. Each condensate thus supports vortex excitation with fractional flux quantum. However the energy of a fractional vortex diverges logarithmically in the thermodynamic limit. In the ground state vortices in different bands are bounded and their normal cores are locked together to form a composite vortex with the standard integer quantum flux. It is interesting to ask whether the vortices in different condensates can decouple under certain conditions. In this talk, I will discuss the dissociation of the composite vortex lattice in the flux flow region when the disparity of superfluid density and coherence length between different bands is large. The fractional vortex lattice in different bands move with different velocities after the dissociation transition, and the dissociation transition shows up as an increase of flux flow resistivity. In the dissociated phase, the Shapiro steps are developed when an ac current is superimposed with a dc current. We also propose to stabilize the fractional vortices by periodic pinning arrays. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering.
Phase-locking of driven vortex lattices with transverse ac force and periodic pinning
Reichhardt, Charles; Kolton, Alejandro B.; Dominguez, Daniel; Gronbech-Jensen, Niels
2001-10-01
For a vortex lattice moving in a periodic array we show analytically and numerically that a new type of phase locking occurs in the presence of a longitudinal dc driving force and a transverse ac driving force. This phase locking is distinct from the Shapiro step phase locking found with longitudinal ac drives. We show that an increase in critical current and a fundamental phase-locked step width scale with the square of the driving ac amplitude. Our results should carry over to other systems such as vortex motion in Josephson-junction arrays.
NASA Technical Reports Server (NTRS)
Lamar, J. E.
1994-01-01
This program represents a subsonic aerodynamic method for determining the mean camber surface of trimmed noncoplaner planforms with minimum vortex drag. With this program, multiple surfaces can be designed together to yield a trimmed configuration with minimum induced drag at some specified lift coefficient. The method uses a vortex-lattice and overcomes previous difficulties with chord loading specification. A Trefftz plane analysis is used to determine the optimum span loading for minimum drag. The program then solves for the mean camber surface of the wing associated with this loading. Pitching-moment or root-bending-moment constraints can be employed at the design lift coefficient. Sensitivity studies of vortex-lattice arrangements have been made with this program and comparisons with other theories show generally good agreement. The program is very versatile and has been applied to isolated wings, wing-canard configurations, a tandem wing, and a wing-winglet configuration. The design problem solved with this code is essentially an optimization one. A subsonic vortex-lattice is used to determine the span load distribution(s) on bent lifting line(s) in the Trefftz plane. A Lagrange multiplier technique determines the required loading which is used to calculate the mean camber slopes, which are then integrated to yield the local elevation surface. The problem of determining the necessary circulation matrix is simplified by having the chordwise shape of the bound circulation remain unchanged across each span, though the chordwise shape may vary from one planform to another. The circulation matrix is obtained by calculating the spanwise scaling of the chordwise shapes. A chordwise summation of the lift and pitching-moment is utilized in the Trefftz plane solution on the assumption that the trailing wake does not roll up and that the general configuration has specifiable chord loading shapes. VLMD is written in FORTRAN for IBM PC series and compatible computers
Cheng, Szu-Cheng; Jheng, Shih-Da
2016-01-01
This paper reports a novel type of vortex lattice, referred to as a bubble crystal, which was discovered in rapidly rotating Bose gases with long-range interactions. Bubble crystals differ from vortex lattices which possess a single quantum flux per unit cell, while atoms in bubble crystals are clustered periodically and surrounded by vortices. No existing model is able to describe the vortex structure of bubble crystals; however, we identified a mathematical lattice, which is a subset of coherent states and exists periodically in the physical space. This lattice is called a von Neumann lattice, and when it possesses a single vortex per unit cell, it presents the same geometrical structure as an Abrikosov lattice. In this report, we extend the von Neumann lattice to one with an integral number of flux quanta per unit cell and demonstrate that von Neumann lattices well reproduce the translational properties of bubble crystals. Numerical simulations confirm that, as a generalized vortex, a von Neumann lattice can be physically realized using vortex lattices in rapidly rotating Bose gases with dipole interatomic interactions. PMID:27545446
Cheng, Szu-Cheng; Jheng, Shih-Da
2016-01-01
This paper reports a novel type of vortex lattice, referred to as a bubble crystal, which was discovered in rapidly rotating Bose gases with long-range interactions. Bubble crystals differ from vortex lattices which possess a single quantum flux per unit cell, while atoms in bubble crystals are clustered periodically and surrounded by vortices. No existing model is able to describe the vortex structure of bubble crystals; however, we identified a mathematical lattice, which is a subset of coherent states and exists periodically in the physical space. This lattice is called a von Neumann lattice, and when it possesses a single vortex per unit cell, it presents the same geometrical structure as an Abrikosov lattice. In this report, we extend the von Neumann lattice to one with an integral number of flux quanta per unit cell and demonstrate that von Neumann lattices well reproduce the translational properties of bubble crystals. Numerical simulations confirm that, as a generalized vortex, a von Neumann lattice can be physically realized using vortex lattices in rapidly rotating Bose gases with dipole interatomic interactions. PMID:27545446
Applications of the unsteady vortex-lattice method in aircraft aeroelasticity and flight dynamics
NASA Astrophysics Data System (ADS)
Murua, Joseba; Palacios, Rafael; Graham, J. Michael R.
2012-11-01
The unsteady vortex-lattice method provides a medium-fidelity tool for the prediction of non-stationary aerodynamic loads in low-speed, but high-Reynolds-number, attached flow conditions. Despite a proven track record in applications where free-wake modelling is critical, other less-computationally expensive potential-flow models, such as the doublet-lattice method and strip theory, have long been favoured in fixed-wing aircraft aeroelasticity and flight dynamics. This paper presents how the unsteady vortex-lattice method can be implemented as an enhanced alternative to those techniques for diverse situations that arise in flexible-aircraft dynamics. A historical review of the methodology is included, with latest developments and practical applications. Different formulations of the aerodynamic equations are outlined, and they are integrated with a nonlinear beam model for the full description of the dynamics of a free-flying flexible vehicle. Nonlinear time-marching solutions capture large wing excursions and wake roll-up, and the linearisation of the equations lends itself to a seamless, monolithic state-space assembly, particularly convenient for stability analysis and flight control system design. The numerical studies emphasise scenarios where the unsteady vortex-lattice method can provide an advantage over other state-of-the-art approaches. Examples of this include unsteady aerodynamics in vehicles with coupled aeroelasticity and flight dynamics, and in lifting surfaces undergoing complex kinematics, large deformations, or in-plane motions. Geometric nonlinearities are shown to play an instrumental, and often counter-intuitive, role in the aircraft dynamics. The unsteady vortex-lattice method is unveiled as a remarkable tool that can successfully incorporate all those effects in the unsteady aerodynamics modelling.
Stabilization of active matter by flow-vortex lattices and defect ordering
NASA Astrophysics Data System (ADS)
Doostmohammadi, Amin; Adamer, Michael F.; Thampi, Sumesh P.; Yeomans, Julia M.
2016-02-01
Active systems, from bacterial suspensions to cellular monolayers, are continuously driven out of equilibrium by local injection of energy from their constituent elements and exhibit turbulent-like and chaotic patterns. Here we demonstrate both theoretically and through numerical simulations, that the crossover between wet active systems, whose behaviour is dominated by hydrodynamics, and dry active matter where any flow is screened, can be achieved by using friction as a control parameter. Moreover, we discover unexpected vortex ordering at this wet-dry crossover. We show that the self organization of vortices into lattices is accompanied by the spatial ordering of topological defects leading to active crystal-like structures. The emergence of vortex lattices, which leads to the positional ordering of topological defects, suggests potential applications in the design and control of active materials.
Stabilization of active matter by flow-vortex lattices and defect ordering.
Doostmohammadi, Amin; Adamer, Michael F; Thampi, Sumesh P; Yeomans, Julia M
2016-01-01
Active systems, from bacterial suspensions to cellular monolayers, are continuously driven out of equilibrium by local injection of energy from their constituent elements and exhibit turbulent-like and chaotic patterns. Here we demonstrate both theoretically and through numerical simulations, that the crossover between wet active systems, whose behaviour is dominated by hydrodynamics, and dry active matter where any flow is screened, can be achieved by using friction as a control parameter. Moreover, we discover unexpected vortex ordering at this wet-dry crossover. We show that the self organization of vortices into lattices is accompanied by the spatial ordering of topological defects leading to active crystal-like structures. The emergence of vortex lattices, which leads to the positional ordering of topological defects, suggests potential applications in the design and control of active materials. PMID:26837846
Stabilization of active matter by flow-vortex lattices and defect ordering
Doostmohammadi, Amin; Adamer, Michael F.; Thampi, Sumesh P.; Yeomans, Julia M.
2016-01-01
Active systems, from bacterial suspensions to cellular monolayers, are continuously driven out of equilibrium by local injection of energy from their constituent elements and exhibit turbulent-like and chaotic patterns. Here we demonstrate both theoretically and through numerical simulations, that the crossover between wet active systems, whose behaviour is dominated by hydrodynamics, and dry active matter where any flow is screened, can be achieved by using friction as a control parameter. Moreover, we discover unexpected vortex ordering at this wet–dry crossover. We show that the self organization of vortices into lattices is accompanied by the spatial ordering of topological defects leading to active crystal-like structures. The emergence of vortex lattices, which leads to the positional ordering of topological defects, suggests potential applications in the design and control of active materials. PMID:26837846
Quantum fluctuations of the vortex-lattice state in an ultrafast rotating Bose gas
Li Qiong; Feng Bo; Li Dingping
2011-04-15
Quantum fluctuations in an ultrafast rotating Bose gas at zero temperature are investigated. We calculate the condensate density perturbatively to show that no condensate is present in the thermodynamic limit. The excitation from Gaussian fluctuations around the mean-field solution causes infrared divergences in loop diagrams, nevertheless, in calculating the atom number density, the correlation functions and the free energy, we find that the sum of the divergences in the same loop order vanishes and we obtain finite physical quantities. The long-range correlation is explored and the algebraic decay exponent for the single-particle correlation function is obtained. The atom number density distribution is obtained at the one-loop level, which illustrates the quantum fluctuation effects to melt the mean-field vortex lattice. By the nonperturbative Gaussian variational method, we locate the spinodal point of the vortex-lattice state.
Quantum fluctuations of the vortex-lattice state in an ultrafast rotating Bose gas
NASA Astrophysics Data System (ADS)
Li, Qiong; Feng, Bo; Li, Dingping
2011-04-01
Quantum fluctuations in an ultrafast rotating Bose gas at zero temperature are investigated. We calculate the condensate density perturbatively to show that no condensate is present in the thermodynamic limit. The excitation from Gaussian fluctuations around the mean-field solution causes infrared divergences in loop diagrams, nevertheless, in calculating the atom number density, the correlation functions and the free energy, we find that the sum of the divergences in the same loop order vanishes and we obtain finite physical quantities. The long-range correlation is explored and the algebraic decay exponent for the single-particle correlation function is obtained. The atom number density distribution is obtained at the one-loop level, which illustrates the quantum fluctuation effects to melt the mean-field vortex lattice. By the nonperturbative Gaussian variational method, we locate the spinodal point of the vortex-lattice state.
Zehetmayer, M
2015-01-01
Order-disorder transitions take place in many physical systems, but observing them in detail in real materials is difficult. In two- or quasi-two-dimensional systems, the transition has been studied by computer simulations and experimentally in electron sheets, dusty plasmas, colloidal and other systems. Here I show the different stages of defect formation in the vortex lattice of a superconductor while it undergoes an order-disorder transition by presenting real-space images of the lattice from scanning tunneling spectroscopy. When the system evolves from the ordered to the disordered state, the predominant kind of defect changes from dislocation pairs to single dislocations, and finally to defect clusters forming grain boundaries. Correlation functions indicate a hexatic-like state preceding the disordered state. The transition in the microscopic vortex distribution is mirrored by the well-known spectacular second peak effect observed in the macroscopic current density of the superconductor. PMID:25784605
Rotating superfluids in anharmonic traps: From vortex lattices to giant vortices
Correggi, Michele; Pinsker, Florian; Rougerie, Nicolas; Yngvason, Jakob
2011-11-15
We study a superfluid in a rotating anharmonic trap and explicate a rigorous proof of a transition from a vortex lattice to a giant vortex state as the rotation is increased beyond a limiting speed determined by the interaction strength. The transition is characterized by the disappearance of the vortices from the annulus where the bulk of the superfluid is concentrated due to centrifugal forces while a macroscopic phase circulation remains. The analysis is carried out within two-dimensional Gross-Pitaevskii theory at large coupling constant and reveals significant differences between ''soft'' anharmonic traps (like a quartic plus quadratic trapping potential) and traps with a fixed boundary: in the latter case the transition takes place in a parameter regime where the size of vortices is very small relative to the width of the annulus, whereas in soft traps the vortex lattice persists until the width of the annulus becomes comparable to the vortex cores. Moreover, the density profile in the annulus where the bulk is concentrated is, in the soft case, approximately Gaussian with long tails and not of the Thomas-Fermi type like in a trap with a fixed boundary.
Morphology of the Superconducting Vortex Lattice in Ultrapure Niobium
NASA Astrophysics Data System (ADS)
Mühlbauer, S.; Pfleiderer, C.; Böni, P.; Laver, M.; Forgan, E. M.; Fort, D.; Keiderling, U.; Behr, G.
2009-04-01
The morphology of the superconducting flux line lattice (FLL) of Nb comprises gradual variations with various lock-in transitions and symmetry breaking rotations. We report a comprehensive small-angle neutron scattering study of the FLL in an ultrapure single crystal of Nb as a function of the orientation of the applied magnetic field. We attribute the general morphology of the FLL and its orientation to three dominant mechanisms; first, nonlocal contributions, second, the transition between open and closed Fermi surface sheets and, third, the intermediate mixed state between the Meissner and the Shubnikov phase.
Gamma-ray superconducting detector based on Abrikosov vortices: Principle of operation
Lisitskiy, M. P.
2009-11-15
The high atomic number of some superconducting elements such as niobium (Z=41) and tantalum (Z=73) and a high material thickness (e.g., t=300 mum) are emphasized as essential properties for development of a gamma-ray solid state detector with high intrinsic detection efficiency in the energy range up to 100 keV. To exploit these properties, a new detection principle based on the interaction of a single gamma-ray photon with Abrikosov vortex is proposed. The interaction of gamma-ray photon with a superconductor is discussed in terms of the photoelectric absorption and a hot-spot formation, the last acts as a short-time pinning center on an Abrikosov vortex and activates its motion, namely, a jump or damped vibration. Both types of vortex motion lead to variation (either static or dynamic) in the magnetic field on the absorber surface. The high sensitivity of the Josephson tunneling to weak magnetic field can be exploited for revealing the magnetic field variation and to make the readout of the detector. Main intrinsic properties of a gamma-ray detector based on Abrikosov vortices are evaluated, including the possibility to measure the energy deposited in the detector. A single Josephson tunnel junction configuration or a superconducting quantum interference device (SQUID) configuration is proposed and discussed as possible realization of working gamma-ray detector both in the counter operation mode and in the radiation spectroscopy operation mode.
Ferromagnetic and antiferromagnetic order in bacterial vortex lattices
NASA Astrophysics Data System (ADS)
Wioland, Hugo; Woodhouse, Francis G.; Dunkel, Jörn; Goldstein, Raymond E.
2016-04-01
Despite their inherently non-equilibrium nature, living systems can self-organize in highly ordered collective states that share striking similarities with the thermodynamic equilibrium phases of conventional condensed-matter and fluid systems. Examples range from the liquid-crystal-like arrangements of bacterial colonies, microbial suspensions and tissues to the coherent macro-scale dynamics in schools of fish and flocks of birds. Yet, the generic mathematical principles that govern the emergence of structure in such artificial and biological systems are elusive. It is not clear when, or even whether, well-established theoretical concepts describing universal thermostatistics of equilibrium systems can capture and classify ordered states of living matter. Here, we connect these two previously disparate regimes: through microfluidic experiments and mathematical modelling, we demonstrate that lattices of hydrodynamically coupled bacterial vortices can spontaneously organize into distinct patterns characterized by ferro- and antiferromagnetic order. The coupling between adjacent vortices can be controlled by tuning the inter-cavity gap widths. The emergence of opposing order regimes is tightly linked to the existence of geometry-induced edge currents, reminiscent of those in quantum systems. Our experimental observations can be rationalized in terms of a generic lattice field theory, suggesting that bacterial spin networks belong to the same universality class as a wide range of equilibrium systems.
Skyrmionic vortex lattices in coherently coupled three-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Orlova, Natalia V.; Kuopanportti, Pekko; Milošević, Milorad V.
2016-08-01
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.
Vortex lattices in the superconducting phases of doped topological insulators and heterostructures
NASA Astrophysics Data System (ADS)
Hung, Hsiang-Hsuan; Ghaemi, Pouyan; Hughes, Taylor L.; Gilbert, Matthew J.
2013-01-01
Majorana fermions are predicted to play a crucial role in condensed matter realizations of topological quantum computation. These heretofore undiscovered quasiparticles have been predicted to exist at the cores of vortex excitations in topological superconductors and in heterostructures of superconductors and materials with strong spin-orbit coupling. In this work, we examine topological insulators with bulk s-wave superconductivity in the presence of a vortex lattice generated by a perpendicular magnetic field. Using self-consistent Bogoliubov-de Gennes calculations, we confirm that beyond the semiclassical, weak-pairing limit the Majorana vortex states appear as the chemical potential is tuned from either side of the band edge so long as the density of states is sufficient for superconductivity to form. Further, we demonstrate that the previously predicted vortex phase transition survives beyond the semiclassical limit. At chemical potential values smaller than the critical chemical potential, the vortex lattice modes hybridize within the top and bottom surfaces, giving rise to a dispersive low-energy mid-gap band. As the chemical potential is increased, the Majorana states become more localized within a single surface but spread into the bulk toward the opposite surface. Eventually, when the chemical potential is sufficiently high in the bulk bands, the Majorana modes can tunnel between surfaces and eventually a critical point is reached at which modes on opposite surfaces can freely tunnel and annihilate leading to the topological phase transition previously studied in the work of Hosur [Phys. Rev. Lett.10.1103/PhysRevLett.107.097001 107, 097001 (2011)].
NASA Astrophysics Data System (ADS)
Lee, Jeongseop; Xin, Yizhou; Halperin, W. P.; Reyes, A. P.; Kuhns, P. L.
The vortex lattice in HgBa2CuO4+δ forms at a vortex melting temperature, Tv, typically ~40K for underdoped crystals with a hole doping ~ 0.11. We present our results from 17O NMR for investigation of the vortex lattice as a function of external magnetic field up to 30 T and temperature as low as 5 K. The vortex contribution to the NMR linewidth can be separated from inhomogeneous broadening by deconvolution of the normal state spectra which was measured separately above, Tv. The vortex melting temperature was measured for two underdoped samples marked by the onset of extra linewidth broadening due to the inhomogeneous magnetic field distribution from the solid vortex lattice consistent with transverse relaxation measurements. We have found evidence for a change in the vortex lattice symmetry as a function of external fields. This work was supported by the DOE BES under Grant No. DE-FG02-05ER46248 and the NHMFL through the NSF and State of Florida.
Vortex lattice structures in YNi{sub 2}B{sub 2}C
Yethiraj, M.; Paul, D.M.; Tomy, C.V.; Forgan, E.M.
1997-12-01
The authors observe a flux lattice with square symmetry in the superconductor YNi{sub 2}B{sub 2}C when the applied field is parallel to the c-axis of the crystal. A square lattice observed previously in the isostructural magnetic analog ErNi{sub 2}B{sub 2}C was attributed to the interaction between magnetic order in that system and the flux lattice. Since the Y-based compound does not order magnetically, it is clear that the structure of the flux lattice is unrelated to magnetic order. In fact, they show that the flux lines have a square cross-section when the applied field is parallel to the c-axis of the crystal, since the measured penetration depth along the 100 crystal direction is larger than the penetration depth along the 110 by approximately 60%. This is the likely reason for the square symmetry of the lattice. Although they find considerable disorder in the arrangement of the flux lines at 2.5T, no melting of the vortex lattice was observed.
Vortex-Loop Unbinding and Flux-Line Lattice Melting in Superconductors
Nguyen, A.K.; Sudbo Hetzel, R. |
1996-08-01
We study the interplay between a novel vortex-loop unbinding in finite magnetic field at {ital T}={ital T}{sub {ital V}} and flux-line-lattice (FLL) melting at {ital T}={ital T}{sub {ital M}} in type-II superconductors. The FLL melts due to nucleation of vortex loops parallel to the {ital {cflx c}} axis, connected to flux lines. For moderate anisotropy, phase coherence parallel to {ital {cflx c}} is lost at {ital T}{sub {ital V}}{approx_gt}{ital T}{sub {ital M}} due to an {ital ab}-plane vortex-loop unbinding with loops located close to thermal FLL fluctuations. For large anisotropy, phase coherence parallel to {ital {cflx c}} is lost at {ital T}{sub {ital V}}{lt}{ital T}{sub {ital M}} due to nucleation of vortex loops uncorrelated to flux lines, predominantly in the {ital ab} plane. {copyright} {ital 1996 The American Physical Society.}
Convergence characteristics of nonlinear vortex-lattice methods for configuration aerodynamics
NASA Technical Reports Server (NTRS)
Seginer, A.; Rusak, Z.; Wasserstrom, E.
1983-01-01
Nonlinear panel methods have no proof for the existence and uniqueness of their solutions. The convergence characteristics of an iterative, nonlinear vortex-lattice method are, therefore, carefully investigated. The effects of several parameters, including (1) the surface-paneling method, (2) an integration method of the trajectories of the wake vortices, (3) vortex-grid refinement, and (4) the initial conditions for the first iteration on the computed aerodynamic coefficients and on the flow-field details are presented. The convergence of the iterative-solution procedure is usually rapid. The solution converges with grid refinement to a constant value, but the final value is not unique and varies with the wing surface-paneling and wake-discretization methods within some range in the vicinity of the experimental result.
Interaction of vortex lattice with ultrasound and the acoustic Faraday effect
Dominguez, D.; Bulaevskii, L.; Ivlev, B.; Maley, M.; Bishop, A.R. |
1995-03-27
The interaction of sound with the vortex lattice is considered for high-{ital T}{sub {ital c}} superconductors, taking into account pinning and electrodynamic forces between vortices and crystal displacements. At low temperatures the Magnus force results in the acoustic Faraday effect; the velocity of sound propagating along the magnetic field depends on the polarization. This effect is linear in the Magnus force and magnetic field in crystals with equivalent {ital a} and {ital b} axes for a field parallel to the {ital c} axis. In the thermally activated flux flow regime, the Faraday effect is caused by electric and magnetic fields induced by vortices and acting on ions.
Cooperative ring exchange and quantum melting of vortex lattices in atomic Bose-Einstein condensates
Ghosh, Tarun Kanti; Baskaran, G.
2004-02-01
Cooperative ring exchange is suggested as a mechanism of quantum melting of vortex lattices in a rapidly rotating quasi-two-dimensional atomic Bose-Einstein condensate (BEC). Using an approach pioneered by Kivelson et al. [Phys. Rev. Lett. 56, 873 (1986)] for the fractional quantized Hall effect, we calculate the condition for quantum melting instability by considering large-correlated ring exchanges in a two-dimensional Wigner crystal of vortices in a strong 'pseudomagnetic field' generated by the background superfluid Bose particles. BEC may be profitably used to address issues of quantum melting of a pristine Wigner solid devoid of complications of real solids.
Effect of Rolling Massage on the Vortex Flow in Blood Vessels with Lattice Boltzmann Simulation
NASA Astrophysics Data System (ADS)
Yi, Hou Hui
The rolling massage manipulation is a classic Chinese Medical Massage, which is a nature therapy in eliminating many diseases. Here, the effect of the rolling massage on the cavity flows in blood vessel under the rolling manipulation is studied by the lattice Boltzmann simulation. The simulation results show that the vortex flows are fully disturbed by the rolling massage. The flow behavior depends on the rolling velocity and the rolling depth. Rolling massage has a better effect on the flows in the cavity than that of the flows in a planar blood vessel. The result is helpful to understand the mechanism of the massage and develop the rolling techniques.
Rossby vortex simulation on a paraboloidal coordinate system using the lattice Boltzmann method.
Yu, H; Zhao, K
2001-11-01
In this paper, we apply our compressible lattice Boltzmann model to a rotating parabolic coordinate system to simulate Rossby vortices emerging in a layer of shallow water flowing zonally in a rotating paraboloidal vessel. By introducing a scaling factor, nonuniform curvilinear mesh can be mapped to a flat uniform mesh and then normal lattice Boltzmann method works. Since the mass per unit area on the two-dimensional (2D) surface varies with the thickness of the water layer, the 2D flow seems to be "compressible" and our compressible model is applied. Simulation solutions meet with the experimental observations qualitatively. Based on this research, quantitative solutions and many natural phenomena simulations in planetary atmospheres, oceans, and magnetized plasma, such as the famous Jovian Giant Red Spot, the Galactic Spiral-vortex, the Gulf Stream, and the Kuroshio Current, etc., can be expected. PMID:11736137
NASA Technical Reports Server (NTRS)
Lamar, J. E.; Herbert, H. E.
1982-01-01
The latest production version, MARK IV, of the NASA-Langley vortex lattice computer program is summarized. All viable subcritical aerodynamic features of previous versions were retained. This version extends the previously documented program capabilities to four planforms, 400 panels, and enables the user to obtain vortex-flow aerodynamics on cambered planforms, flowfield properties off the configuration in attached flow, and planform longitudinal load distributions.
NASA Technical Reports Server (NTRS)
Herbert, H. E.; Lamar, J. E.
1982-01-01
The source code for the latest production version, MARK IV, of the NASA-Langley Vortex Lattice Computer Program is presented. All viable subcritical aerodynamic features of previous versions were retained. This version extends the previously documented program capabilities to four planforms, 400 panels, and enables the user to obtain vortex-flow aerodynamics on cambered planforms, flowfield properties off the configuration in attached flow, and planform longitudinal load distributions.
Dynamic and Structural Studies of Metastable Vortex Lattice Domains in MgB2
NASA Astrophysics Data System (ADS)
de Waard, E. R.; Kuhn, S. J.; Rastovski, C.; Eskildsen, M. R.; Leishman, A.; Dewhurst, C. D.; Debeer-Schmitt, L.; Littrell, K.; Karpinski, J.; Zhigadlo, N. D.
Small-angle neutron scattering (SANS) studies of the vortex lattice (VL) in the type-II superconductor MgB2 have revealed an unprecedented degree of metastability that is demonstrably not due to vortex pinning, [C. Rastovski et al . , Phys. Rev. Lett. 111, 107002 (2013)]. The VL can be driven to the GS through successive application of an AC magnetic field. Here we report on detailed studies of the transition kinetics and structure of the VL domains. Stroboscopic studies of the transition revealed a stretched exponential decrease of the metastable volume fraction as a function of the number of applied AC cycles, with subtle differences depending on whether the AC field is oriented parallel or perpendicular to the DC field used to create the VL. We speculate the slower transition kinetics for the transverse AC field may be due to vortex cutting. Spatial studies include scanning SANS measurements showing the VL domain distribution within the MgB2 single crystal as well as measurements of VL correlation lengths. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-FG02-10ER46783.
NASA Astrophysics Data System (ADS)
Guillamon, I.; Vieira, S.; Suderow, H.; Cordoba, R.; Sese, J.; de Teresa, J. M.; Ibarra, R.
In two dimensional (2D) systems, theory has proposed that random disorder destroys long range correlations driving a transition to a glassy state. Here, I will discuss new insights into this issue obtained through the direct visualization of the critical behaviour of a 2D superconducting vortex lattice formed in a thin film with a smooth 1D thickness modulation. Using scanning tunneling microscopy at 0.1K, we have tracked the modification in the 2D vortex arrangements induced by the 1D thickness modulation while increasing the vortex density by three orders of magnitude. Upon increasing the field, we observed a two-step order-disorder transition in the 2D vortex lattice mediated by the appearance of dislocations and disclinations and accompanied by an increase in the local vortex density fluctuations. Through a detailed analysis of correlation functions, we find that the transition is driven by the incommensurate 1D thickness modulation. We calculate the critical points and exponents and find that they are well above theoretical expectation for random disorder. Our results show that long range 1D correlations in random potentials enhance the stability range of the ordered phase in a 2D vortex lattice. Work supported by Spanish MINECO, CIG Marie Curie Grant, Axa Research Fund and FBBVA.
Vortex Lattice Studies in CeCoIn₅ with H⊥c
Das, P.; White, J. S.; Holmes, A. T.; Gerber, S.; Forgan, E. M.; Bianchi, A. D.; Kenzelmann, M.; Zolliker, M.; Gavilano, J. L.; Bauer, E. D.; et al
2012-02-23
We present small angle neutron scattering studies of the vortex lattice (VL) in CeCoIn₅ with magnetic fields applied parallel (H) to the antinodal [100] and nodal [110] directions. For H II 100], a single VL orientation is observed, while a 90° reorientation transition is found for H II [110]. For both field orientations and VL configurations we find a distorted hexagonal VL with an anisotropy, Γ=2.0±0.05. The VL form factor shows strong Pauli paramagnetic effects similar to what have previously been reported for H II [001]. At high fields, above which the upper critical field (Hc2) becomes a first-order transition,more » an increased disordering of the VL is observed.« less
Vortex Lattice Studies in CeCoIn₅ with H⊥c
Das, P.; White, J. S.; Holmes, A. T.; Gerber, S.; Forgan, E. M.; Bianchi, A. D.; Kenzelmann, M.; Zolliker, M.; Gavilano, J. L.; Bauer, E. D.; Sarrao, J. L.; Petrovic, C.; Eskildsen, M. R.
2012-02-23
We present small angle neutron scattering studies of the vortex lattice (VL) in CeCoIn₅ with magnetic fields applied parallel (H) to the antinodal [100] and nodal [110] directions. For H II 100], a single VL orientation is observed, while a 90° reorientation transition is found for H II [110]. For both field orientations and VL configurations we find a distorted hexagonal VL with an anisotropy, Γ=2.0±0.05. The VL form factor shows strong Pauli paramagnetic effects similar to what have previously been reported for H II [001]. At high fields, above which the upper critical field (H_{c2}) becomes a first-order transition, an increased disordering of the VL is observed.
Quantum melting of a two-dimensional vortex lattice at zero temperature
Rozhkov, A.; Stroud, D.
1996-11-01
We consider the quantum melting of a two-dimensional flux lattice at temperature {ital T} = 0 in the {open_quote}{open_quote}superclean limit.{close_quote}{close_quote} In this regime, we find that vortex motion is dominated by the Magnus force. A Lindemann criterion predicts melting when {ital n}{sub {ital v}}/{ital n}{sub {ital p}}{ge}{beta}, where {ital n}{sub {ital v}} and {ital n}{sub {ital p}} are the areal number densities of vortex pancakes and Cooper pairs, and {beta}{approx_equal}0.1. A second criterion is derived by using Wigner-crystal and Laughlin wave functions for the solid and liquid phases respectively, and setting the two energies equal. This gives a melting value similar to the Lindemann result. We discuss the numerical value of the {ital T}=0 melting field for thin layers of a low-{ital T}{sub {ital c}} superconductor, such as {ital a}-MoGe, and single layers of high-{ital T}{sub {ital c}} materials. {copyright} {ital 1996 The American Physical Society.}
Vortex confinement by magnetic domains in superconductor-ferromagnet bilayers
NASA Astrophysics Data System (ADS)
Cieplak, Marta Z.; Adamus, Z.; Konczykowski, M.; Zhu, L. Y.; Chien, C. L.; Cheng, X. M.
2013-03-01
We use a line of miniature Hall sensors to study the effect of magnetic-domain-induced vortex confinement on the flux dynamics in a superconductor/ferromagnet bilayer. A single tunable bilayer is built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in between to avoid proximity effect. The magnetic domain patterns of various geometries are reversibly predefined in the Co/Pt multilayer using the appropriate magnetization procedure. The magnetic domain geometry strongly affects vortex dynamics, leading to geometry-dependent trapping of vortices at the sample edge, nonuniform flux penetration, and strongly nonuniform critical current density. With the decreasing temperature the magnetic pinning increases but this increase is substantially weaker than that of the intrinsic pinning. The analysis of the initial flux penetration suggests that vortices may form various vortex structures, including disordered Abrikosov lattice or single and double vortex chains, in which minimal vortex-vortex distance is comparable to the magnetic penetration depth. Supported by Polish NCS grant 2011/01/B/ST3/00462, by the French-Polish Program PICS 2012, by EU grant POIG.01.01.02-00-108/09, and by NSF grants DMR05-20491 and DMR-1053854.
Resonant impedance matching of Abrikosov vortex-flow transistors
Hohenwarter, G.K.G. ); Martens, J.S.; Beyer, J.B.; Nordman, J.E. . Dept. of Electrical and Computer Engineering)
1991-03-01
This paper reports that the authors achieved impedance matching to low input impedance flux-flow devices with transmission line resonators. A gain of 15 db in a 50{Omega} system was predicted by simulations of the amplifier. The design, layout and fabrication of an amplifier and an oscillator circuit will be presented. Circuit layout and fabrication of YBCO and T1 based circuits is briefly described. Measurements performed on fabricated circuits show a gain of 10 db at 4 GHz for an amplifier circuit and an output power of {minus}73 dbm at 7.1 GHz for an oscillator circuit.
NASA Technical Reports Server (NTRS)
Lan, C. E.
1981-01-01
The nonplanar quasi-vortex-lattice method is applied to the calculation of lateral-directional stability derivatives of wings with and without vortex-lift effect. Results for conventional configurations and those with winglets, V-tail, etc. are compared with available data. All rolling moment derivatives are found to be accurately predicted. The prediction of side force and yawing moment derivatives for some configurations is not as accurate. Causes of the discrepancy are discussed. A user's manual for the program and the program listing are also included.
NASA Technical Reports Server (NTRS)
Lamar, J. E.; Gloss, B. B.
1975-01-01
Because the potential flow suction along the leading and side edges of a planform can be used to determine both leading- and side-edge vortex lift, the present investigation was undertaken to apply the vortex-lattice method to computing side-edge suction force for isolated or interacting planforms. Although there is a small effect of bound vortex sweep on the computation of the side-edge suction force, the results obtained for a number of different isolated planforms produced acceptable agreement with results obtained from a method employing continuous induced-velocity distributions. By using the method outlined, better agreement between theory and experiment was noted for a wing in the presence of a canard than was previously obtained.
Superconducting gap and vortex lattice of the heavy-fermion compound CeCu2Si2
NASA Astrophysics Data System (ADS)
Enayat, Mostafa; Sun, Zhixiang; Maldonado, Ana; Suderow, Hermann; Seiro, Silvia; Geibel, Christoph; Wirth, Steffen; Steglich, Frank; Wahl, Peter
2016-01-01
The order parameter and pairing mechanism for superconductivity in heavy-fermion compounds are still poorly understood. Scanning tunneling microscopy and spectroscopy at ultralow temperatures can yield important information about the superconducting order parameter and the gap structure. Here, we study the first heavy-fermion superconductor, CeCu2Si2 . Our data show the superconducting gap which is not fully formed and exhibits features that point to a multigap order parameter. Spatial mapping of the zero-bias conductance in magnetic field reveals the vortex lattice, which allows us to unequivocally link the observed conductance gap to superconductivity in CeCu2Si2 . The vortex lattice is found to be predominantly triangular with distortions at fields close to ˜0.7 Hc 2 .
NASA Technical Reports Server (NTRS)
Hall, G. F.
1975-01-01
The application is considered of vortex lattice techniques to the problem of describing the aerodynamics and performance of statically thrusting propellers. A numerical lifting surface theory to predict the aerodynamic forces and power is performed. The chordwise and spanwise loading is modelled by bound vortices fixed to a twisted flat plate surface. In order to eliminate any apriori assumptions regarding the wake shape, it is assumed the propeller starts from rest. The wake is generated in time and allowed to deform under its own self-induced velocity field as the motion of the propeller progresses. The bound circulation distribution is then determined with time by applying the flow tangency boundary condition at certain selected control points on the blades. The aerodynamics of the infinite wing and finite wing are also considered. The details of wake formation and roll-up are investigated, particularly the localized induction effect. It is concluded that proper wake roll-up and roll-up rates can be established by considering the details of motion at the instant of start.
Localization of a Bose-Einstein-condensate vortex in a bichromatic optical lattice
Adhikari, S. K.
2010-04-15
By numerical simulation of the time-dependent Gross-Pitaevskii equation we show that a weakly interacting or noninteracting Bose-Einstein condensate (BEC) vortex can be localized in a three-dimensional bichromatic quasiperiodic optical-lattice (OL) potential generated by the superposition of two standing-wave polarized laser beams with incommensurate wavelengths. We also study the localization of a (nonrotating) BEC in two and three dimensions by bichromatic OL potentials along orthogonal directions. This is a generalization of the localization of a BEC in a one-dimensional bichromatic OL as studied in a recent experiment [Roati et al., Nature 453, 895 (2008)]. We demonstrate the stability of the localized state by considering its time evolution in the form of a stable breathing oscillation in a slightly altered potential for a large period of time. Finally, we consider the localization of a BEC in a random one-dimensional potential in the form of several identical repulsive spikes arbitrarily distributed in space.
NASA Technical Reports Server (NTRS)
Chaparro, Daniel; Fujiwara, Gustavo E. C.; Ting, Eric; Nguyen, Nhan
2016-01-01
The need to rapidly scan large design spaces during conceptual design calls for computationally inexpensive tools such as the vortex lattice method (VLM). Although some VLM tools, such as Vorview have been extended to model fully-supersonic flow, VLM solutions are typically limited to inviscid, subcritical flow regimes. Many transport aircraft operate at transonic speeds, which limits the applicability of VLM for such applications. This paper presents a novel approach to correct three-dimensional VLM through coupling of two-dimensional transonic small disturbance (TSD) solutions along the span of an aircraft wing in order to accurately predict transonic aerodynamic loading and wave drag for transport aircraft. The approach is extended to predict flow separation and capture the attenuation of aerodynamic forces due to boundary layer viscosity by coupling the TSD solver with an integral boundary layer (IBL) model. The modeling framework is applied to the NASA General Transport Model (GTM) integrated with a novel control surface known as the Variable Camber Continuous Trailing Edge Flap (VCCTEF).
Description, Usage, and Validation of the MVL-15 Modified Vortex Lattice Analysis Capability
NASA Technical Reports Server (NTRS)
Ozoroski, Thomas A.
2015-01-01
MVL-15 is the most recent version of the Modified Vortex-Lattice (MVL) code developed within the Aerodynamics Systems Analysis Branch (ASAB) at NASA LaRC. The term "modified" refers to the primary modification of the core vortex-lattice methodology: inclusion of viscous aerodynamics tables that are linked to the linear solution via iterative processes. The inclusion of the viscous aerodynamics inherently converts the MVL-15 from a purely analytic linearized method to a semi-empirical blend which retains the rapid execution speed of the linearized method while empirically characterizing the section aerodynamics at all spanwise lattice points. The modification provides a means to assess non-linear effects on lift that occur at angles of attack near stall, and provides a means to determine the drag associated with the application of design strategies for lift augmentation such as the use of flaps or blowing. The MVL-15 code is applicable to the analyses of aircraft aerodynamics during cruise, but it is most advantageously applied to the analysis of aircraft operating in various high-lift configurations. The MVL methodology has been previously conceived and implemented; the initial concept version was delivered to the ASAB in 2001 (van Dam, C.), subsequently revised (Gelhausen, P. and Ozoroski, T. 2002 / AVID Inc., Gelhausen, P., and Roberts, M. 2004), and then overhauled (Ozoroski, T., Hahn, A. 2008). The latest version, MVL-15 has been refined to provide analysis transparency and enhanced to meet the analysis requirements of the Environmentally Responsible Aviation (ERA) Project. Each revision has been implemented with reasonable success. Separate applications of the methodology are in use, including a similar in-house capability, developed by Olson, E. that is tailored for structural and acoustics analyses. A central premise of the methodology is that viscous aerodynamic data can be associated with analytic inviscid aerodynamic results at each spanwise wing section
NASA Astrophysics Data System (ADS)
Herrera-Vasco, Edwin; Guillamon, Isabel; Fente, Anton; Galvis, Jose; Correa, Alexandre; Luccas, Roberto; Mompean, Federico; Garcia Hernandez, Mar; Brison, Jean P.; Vieira, Sebastian; Suderow, Hermann
We present very low-temperature scanning tunneling microscopy (STM) experiments on the superconductor β-Bi2 Pd. We find a single superconducting gap from the zero-field tunneling conductance. We also find that the hexagonal vortex lattice is locked to the square atomic lattice. The magnetic field dependence of the intervortex tunneling conductance is higher than the one expected in a single-gap superconductor. Such an increase in the intervortex tunneling conductance has been found in superconductors with multiple superconducting gaps. We fit the upper critical field Hc2(T) and show that multiband Fermi surface is needed to explain the observed behavior. We propose that β-Bi2Pd is a single-gap multiband superconductor. We have measured the tilted vortex lattice (TVL) using a three axis superconducting magnet. Our results give first real space imaging of the TVL in a nearly isotropic s-wave BCS superconductor. From a detailed study of the TVL varying polar and azimuthal angles, we find correlations between the square atomic lattice and the TVL.
NASA Astrophysics Data System (ADS)
Nonomura, Y.; Hu, X.
2004-10-01
Structures of flux-line lattices (FLL) in vortex states of high- Tc superconductors in a tilted field are directly studied by Monte Carlo simulations of the three-dimensional anisotropic XY model, where only Josephson couplings are considered between superconducting layers. A nontrivial structural transition between the Josephson-dominant and Abrikosov-dominant FLL phases occurs as the tilting angle of the external field is increased at low enough temperatures. A similar phase transition is observed by varying the anisotropy parameter with a fixed external field. A finite latent heat at the transition point indicates that this phase transition is of first order.
NASA Astrophysics Data System (ADS)
Ge, Jun-Yi; Gutierrez, Joffre; Lyashchenko, A.; Filipov, V.; Li, Jun; Moshchalkov, Victor V.
2014-11-01
In nature, many systems exhibit modulated phases with periodic macroscopic patterns and textures mainly due to the competitive interactions of different phases. Vortex systems in superconductors, which are easy to access, offer the possibility of tuning the ratio between the competitive interactions, providing a unique tool to study the evolution and equilibrium of similar patterns. The κ -T phase diagram of clean superconductors shows the transition from type-I to type-II superconductivity via a narrow κ range near the dual point κ =1 /√{2 } where the vortices attract each other at long distances and repel each other at short distances. This κ range, which is termed the type-II/1 phase, becomes larger with decreasing temperature. The direct imaging at the scale of individual vortices of the vortex pattern transition would provide valuable information. Therefore, by using scanning Hall probe microscopy, we have performed direct visualization of the vortex pattern transition in a ZrB12 single crystal across the type-II and type-II/1 phases. By gradually lowering the temperature, and thereby tuning vortex interactions, a transition is observed from the ordered Abrikosov vortex lattice to a disordered vortex pattern with large areas of Meissner phase, vortex chains, and vortex clusters. The formation of vortex chains and clusters has been found to arise from the combined effect of quenched disorder and the attractive vortex-vortex interaction in the type-II/1 phase. The clusters and chains serve as the vortex reservoir to enable the formation of a triangular vortex lattice of the type-II phase at high temperatures.
NASA Astrophysics Data System (ADS)
Zhang, Jianying; Yan, Guangwu; Wang, Moran
2016-02-01
A lattice Boltzmann model for solving the three-dimensional cubic-quintic complex Ginzburg-Landau equation (CQCGLE) is proposed. Differently from the classic lattice Boltzmann models, this lattice Boltzmann model is based on uniformly distributed lattice points in a three-dimensional space, and the evolution of the model is about a spatial axis rather than time. The algorithm provides advantages similar to the lattice Boltzmann method in that it is easily adapted to complex Ginzburg-Landau equations. Examples show that the model accurately reproduces the vortex tori pattern in the CQCGLE.
Johnson, T H; Yuan, Y; Bao, W; Clark, S R; Foot, C; Jaksch, D
2016-06-17
We investigate cold bosonic impurity atoms trapped in a vortex lattice formed by condensed bosons of another species. We describe the dynamics of the impurities by a bosonic Hubbard model containing occupation-dependent parameters to capture the effects of strong impurity-impurity interactions. These include both a repulsive direct interaction and an attractive effective interaction mediated by the Bose-Einstein condensate. The occupation dependence of these two competing interactions drastically affects the Hubbard model phase diagram, including causing the disappearance of some Mott lobes. PMID:27367366
NASA Astrophysics Data System (ADS)
Johnson, T. H.; Yuan, Y.; Bao, W.; Clark, S. R.; Foot, C.; Jaksch, D.
2016-06-01
We investigate cold bosonic impurity atoms trapped in a vortex lattice formed by condensed bosons of another species. We describe the dynamics of the impurities by a bosonic Hubbard model containing occupation-dependent parameters to capture the effects of strong impurity-impurity interactions. These include both a repulsive direct interaction and an attractive effective interaction mediated by the Bose-Einstein condensate. The occupation dependence of these two competing interactions drastically affects the Hubbard model phase diagram, including causing the disappearance of some Mott lobes.
Tuning vortex confinement by magnetic domains in a superconductor/ferromagnet bilayer
NASA Astrophysics Data System (ADS)
Cieplak, Marta Z.; Adamus, Z.; Kończykowski, M.; Zhu, L. Y.; Cheng, X. M.; Chien, C. L.
2013-01-01
We use a line of miniature Hall sensors to study the effect of magnetic-domain-induced vortex confinement on the flux dynamics in a superconductor/ferromagnet bilayer. A single tunable bilayer is built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in-between to avoid the proximity effect. The magnetic-domain patterns of various geometries are reversibly predefined in the Co/Pt multilayer using the appropriate magnetization procedure. The magnetic-domain geometry strongly affects vortex dynamics, leading to geometry-dependent trapping of vortices at the sample edge, nonuniform flux penetration, and strongly nonuniform critical current density. With the decreasing temperature, the magnetic pinning increases, but this increase is substantially weaker than that of the intrinsic pinning. The analysis of the initial flux penetration suggests that vortices may form various vortex structures, including disordered Abrikosov lattice or single and double vortex chains, in which minimal vortex-vortex distance is comparable to the magnetic penetration depth.
DC to AC converter on Abrikosov vortices in a washboard pinning potential
NASA Astrophysics Data System (ADS)
Shklovskij, Valerij A.; Dobrovolskiy, Oleksandr V.
2014-05-01
The nonlinear dynamics of Abrikosov vortices in a cosine dc-biased washboard pinning potential at nonzero temperature is theoretically investigated. The problem is treated relying upon the exact solution of the Langevin equation for non-interacting vortices by using the Fokker-Planck method combined with the scalar continued fractions technique. The time variation of the local mean vortex velocity v(t) is calculated. The time voltage E(t) ~ v(t) is predicted to oscillate with a dc current-dependent frequency and a tunable pulse shape. Formulas for v(t) are discussed as functions of dc transport current and temperature, in a wide range of the corresponding dimensionless parameters. The derived expressions can be adapted for a number of physical applications utilizing the overdamped motion of a Brownian particle in a tilted cosine potential, e.g., the resistively shunted Josephson junction model.
NASA Astrophysics Data System (ADS)
Jiang, Xiaohai; Lee, Taehun; Andreopoulos, Yiannis; Wang, Zhexuan
2013-11-01
Vortex-induced vibrations (VIV) phenomena related to self-excited energy harvesters consisting of circular or square cylinders have been investigated numerically by using the BGK or MRT Lattice Boltzmann Method. In the present work such a harvester is placed inside a channel flow and is allowed to oscillate without a structural restoring force in a direction normal to the flow. Currently the half-way bounce-back boundary scheme and interpolations are being used to model the moving boundary. The numerical results were compared to the ones by classical CFD methods and experiments. A good agreement was obtained. The vortex dynamics and the development of the flow patterns for different flow parameters such as Reynolds number, blockage and aspect ratios will be presented. Particular emphasis is given to the dynamics of vortex pairing observed in several of the simulations. The present approach will be extended to simulate the flexible beam with the Immersed Boundary Method. Sponsored by the National Science Foundation (CBET #1033117) and a fellowship support from China Scholarship Council.
Aerodynamic Analysis of the Truss-Braced Wing Aircraft Using Vortex-Lattice Superposition Approach
NASA Technical Reports Server (NTRS)
Ting, Eric Bi-Wen; Reynolds, Kevin Wayne; Nguyen, Nhan T.; Totah, Joseph J.
2014-01-01
The SUGAR Truss-BracedWing (TBW) aircraft concept is a Boeing-developed N+3 aircraft configuration funded by NASA ARMD FixedWing Project. This future generation transport aircraft concept is designed to be aerodynamically efficient by employing a high aspect ratio wing design. The aspect ratio of the TBW is on the order of 14 which is significantly greater than those of current generation transport aircraft. This paper presents a recent aerodynamic analysis of the TBW aircraft using a conceptual vortex-lattice aerodynamic tool VORLAX and an aerodynamic superposition approach. Based on the underlying linear potential flow theory, the principle of aerodynamic superposition is leveraged to deal with the complex aerodynamic configuration of the TBW. By decomposing the full configuration of the TBW into individual aerodynamic lifting components, the total aerodynamic characteristics of the full configuration can be estimated from the contributions of the individual components. The aerodynamic superposition approach shows excellent agreement with CFD results computed by FUN3D, USM3D, and STAR-CCM+. XXXXX Demand for green aviation is expected to increase with the need for reduced environmental impact. Most large transports today operate within the best cruise L/D range of 18-20 using the conventional tube-and-wing design. This configuration has led to marginal improvements in aerodynamic efficiency over this past century, as aerodynamic improvements tend to be incremental. A big opportunity has been shown in recent years to significantly reduce structural weight or trim drag, hence improved energy efficiency, with the use of lightweight materials such as composites. The Boeing 787 transport is an example of a modern airframe design that employs lightweight structures. High aspect ratio wing design can provide another opportunity for further improvements in energy efficiency. Historically, the study of high aspect ratio wings has been intimately tied to the study of
NASA Astrophysics Data System (ADS)
Vahala, George; Yepez, Jeffrey; Vahala, Linda
2008-04-01
The ground state wave function for a Bose Einstein condensate is well described by the Gross-Pitaevskii equation. A Type-II quantum algorithm is devised that is ideally parallelized even on a classical computer. Only 2 qubits are required per spatial node. With unitary local collisions, streaming of entangled states and a spatially inhomogeneous unitary gauge rotation one recovers the Gross-Pitaevskii equation. Quantum vortex reconnection is simulated - even without any viscosity or resistivity (which are needed in classical vortex reconnection).
Exotic vortex lattices in a rotating binary dipolar Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Zhang, Xiao-Fei; Wen, Lin; Dai, Cai-Qing; Dong, Rui-Fang; Jiang, Hai-Feng; Chang, Hong; Zhang, Shou-Gang
2016-01-01
In the last decade, considerable advances have been made in the investigation of dipolar quantum gases. Previous theoretical investigations of a rotating binary dipolar Bose-Einstein condensate, where only one component possesses dipole moment, were mainly focused on two special orientations of the dipoles: perpendicular or parallel to the plane of motion. Here we study the ground-state and rotational properties of such a system for an arbitrary orientation of the dipoles. We demonstrate the ground-state vortex structures depend strongly on the relative strength between dipolar and contact interactions and the rotation frequency, as well as on the orientation of the dipoles. In the absence of rotation, the tunable dipolar interaction can be used to induce the squeezing or expansion of the cloud, and to derive the phase transition between phase coexistence and separation. Under finite rotation, the system is found to exhibit exotic ground-state vortex configurations, such as kernel-shell, vortex necklace, and compensating stripe vortex structures. We also check the validity of the Feynman relation, and find no significant deviations from it. The obtained results open up alternate ways for the quantum control of dipolar quantum gases.
Exotic vortex lattices in a rotating binary dipolar Bose-Einstein condensate.
Zhang, Xiao-Fei; Wen, Lin; Dai, Cai-Qing; Dong, Rui-Fang; Jiang, Hai-Feng; Chang, Hong; Zhang, Shou-Gang
2016-01-01
In the last decade, considerable advances have been made in the investigation of dipolar quantum gases. Previous theoretical investigations of a rotating binary dipolar Bose-Einstein condensate, where only one component possesses dipole moment, were mainly focused on two special orientations of the dipoles: perpendicular or parallel to the plane of motion. Here we study the ground-state and rotational properties of such a system for an arbitrary orientation of the dipoles. We demonstrate the ground-state vortex structures depend strongly on the relative strength between dipolar and contact interactions and the rotation frequency, as well as on the orientation of the dipoles. In the absence of rotation, the tunable dipolar interaction can be used to induce the squeezing or expansion of the cloud, and to derive the phase transition between phase coexistence and separation. Under finite rotation, the system is found to exhibit exotic ground-state vortex configurations, such as kernel-shell, vortex necklace, and compensating stripe vortex structures. We also check the validity of the Feynman relation, and find no significant deviations from it. The obtained results open up alternate ways for the quantum control of dipolar quantum gases. PMID:26778736
Exotic vortex lattices in a rotating binary dipolar Bose-Einstein condensate
Zhang, Xiao-Fei; Wen, Lin; Dai, Cai-Qing; Dong, Rui-Fang; Jiang, Hai-Feng; Chang, Hong; Zhang, Shou-Gang
2016-01-01
In the last decade, considerable advances have been made in the investigation of dipolar quantum gases. Previous theoretical investigations of a rotating binary dipolar Bose-Einstein condensate, where only one component possesses dipole moment, were mainly focused on two special orientations of the dipoles: perpendicular or parallel to the plane of motion. Here we study the ground-state and rotational properties of such a system for an arbitrary orientation of the dipoles. We demonstrate the ground-state vortex structures depend strongly on the relative strength between dipolar and contact interactions and the rotation frequency, as well as on the orientation of the dipoles. In the absence of rotation, the tunable dipolar interaction can be used to induce the squeezing or expansion of the cloud, and to derive the phase transition between phase coexistence and separation. Under finite rotation, the system is found to exhibit exotic ground-state vortex configurations, such as kernel-shell, vortex necklace, and compensating stripe vortex structures. We also check the validity of the Feynman relation, and find no significant deviations from it. The obtained results open up alternate ways for the quantum control of dipolar quantum gases. PMID:26778736
Chandra Ganguli, Somesh; Singh, Harkirat; Saraswat, Garima; Ganguly, Rini; Bagwe, Vivas; Shirage, Parasharam; Thamizhavel, Arumugam; Raychaudhuri, Pratap
2015-01-01
The vortex lattice in a Type II superconductor provides a versatile model system to investigate the order-disorder transition in a periodic medium in the presence of random pinning. Here, using scanning tunnelling spectroscopy in a weakly pinned Co0.0075NbSe2 single crystal, we show that the vortex lattice in a 3-dimensional superconductor disorders through successive destruction of positional and orientational order, as the magnetic field is increased across the peak effect. At the onset of the peak effect, the equilibrium quasi-long range ordered state transforms into an orientational glass through the proliferation of dislocations. At a higher field, the dislocations dissociate into isolated disclination giving rise to an amorphous vortex glass. We also show the existence of a variety of additional non-equilibrium metastable states, which can be accessed through different thermomagnetic cycling. PMID:26039699
NASA Astrophysics Data System (ADS)
Kuhn, S. J.; Kawano-Furukawa, H.; Jellyman, E.; Riyat, R.; Forgan, E. M.; Ono, M.; Kihou, K.; Lee, C. H.; Hardy, F.; Adelmann, P.; Wolf, Th.; Meingast, C.; Gavilano, J.; Eskildsen, M. R.
2016-03-01
We study the intrinsic anisotropy of the superconducting state in KFe2As2 by using small-angle neutron scattering to image the vortex lattice as the applied magnetic field is rotated towards the FeAs crystalline planes. The anisotropy is found to be strongly field dependent, indicating multiband superconductivity. Furthermore, the high-field anisotropy significantly exceeds that of the upper critical field, providing further support for Pauli limiting in KFe2As2 for fields applied in the basal plane. The effect of Pauli paramagnetism on the unpaired quasiparticles in the vortex cores is directly evident from the ratio of scattered intensities due to the longitudinal and transverse vortex lattice field modulation.
Das, Pinaki; Rastovski, Catherine; O'Brien, Timothy; Schlesinger, Kimberly; Dewhurst, Charles; Debeer-Schmitt, Lisa M; Zhigadlo, Nikolai; Karpinski, Janusz; Eskildsen, Morten
2012-01-01
The vortex lattice (VL) symmetry and orientation in clean type-II superconductors depends sensitively on the host material anisotropy, vortex density and temperature, frequently leading to rich phase diagrams. Typically, a well-ordered VL is taken to imply a ground-state configuration for the vortex-vortex interaction. Using neutron scattering we studied the VL in MgB2 for a number of field-temperature histories, discovering an unprecedented degree of metastability in connection with a known, second-order rotation transition. This allows, for the first time, structural studies of a well-ordered, nonequilibrium VL. While the mechanism responsible for the longevity of the metastable states is not resolved, we speculate it is due to a jamming of VL domains, preventing a rotation to the ground-state orientation.
Origin of Spontaneous Broken Mirror Symmetry of Vortex Lattices in Nb
NASA Astrophysics Data System (ADS)
Adachi, Hiroki M.; Ishikawa, Masaki; Hirano, Tomoya; Ichioka, Masanori; Machida, Kazushige
2011-11-01
Combining the microscopic Eilenberger theory with the first-principles band calculation, we investigate the stable flux line lattice (FLL) for a field applied to the fourfold axis, i.e., H\\parallel [001] in cubic Nb. The observed FLL transformation along Hc2 is almost perfectly explained without using adjustable parameter, including the tilted square, scalene triangle with broken mirror symmetry, and isosceles triangle lattices upon increasing T. We construct a minimum Fermi surface model to understand such morphologies, particularly the stability of the scalene triangle lattice attributed to the lack of mirror symmetry about the Fermi velocity maximum direction in k-space.
Anomalous magnetization due to the vortex lattice melting transition in YBa{sub 2}Cu{sub 3}O{sub y}
Nishizaki, Terukazu; Onodera, Yasuaki; Naito, Tomoyuki; Kobayashi, Norio
1996-12-01
Magnetization measurements in YBa{sub 2}Cu{sub 3}O{sub y} single crystals are performed as a function of the temperature T and the magnetic field H. It is found that an anomalous magnetization step which provides the thermodynamic evidence of the first-order vortex lattice melting transition and the resistive kink with the hysteresis are observed in the same phase boundary in H-T plane. For samples with a small value of the irreversibility field H{sub irr}(T) as compared with the vortex lattice melting line H{sub m}(T), the vortex lattice melting is observed in the reversible magnetization region and the entropy change per vortex per CuO{sub 2} layer at the transition is estimated to be {Delta}s {approx_equal} 0.5 - 1.0 k{sub B}. For samples with a slightly larger value of H{sub irr}(T) comparable to H{sub m}(T), on the other hand, the jump height and the value of {Delta}s is enhanced. Thus, the value of {Delta}s is affected significantly by the relation between H{sub irr}(T) which varies from sample to sample and H{sub m}(T) which is an universal line.
Anisotropic vortex lattice in YBa[sub 2]Cu[sub 3]O[sub 7
Yethiraj, M.; Mook, H.A.; Wignall, G.D.; Cubitt, R.; Forgan, E.M.; Lee, S.L.; Paul, D.M.; Armstrong, T. Superconductivity Research Group, University of Birmingham, Birmingham B15 2TT Physik-Institut der Universitaet Zuerich, Schoenberggasse 9, CH 8001, Zuerich Department of Physics, University of Warwick, Coventry CV4 7AL Allied Signal Research Laboratories, Torrance, California 90509 )
1993-11-01
We report on small angle neutron scattering observations of the flux line lattice (FLL) in a single crystal of YBa[sub 2]Cu[sub 3]O[sub 7]. To probe the mass anisotropy ratio, [ital m][sub 3]/[ital m][sub 1], measurements were made as a function of angle, [Theta], between the 8 kOe applied field and the crystallographic (001) axis for 0[degree][le][Theta][le]80[degree]. With the rotation about an [ital a]/[ital b] (or [ital y]) axis, two symmetry-related distorted hexagonal FLL domains formed. Contrary to theoretical prediction, the lattices formed are consistent with a rotation of the short basis vector, [bold a][sub 1], from the [ital x] axis by 15[degree], after the effects of anisotropy are removed. The mass ratio is 20[plus minus]2, which is slightly lower than published values. The temperature dependence of the intensity is not conventional.
Singularimetry of local phase gradients using vortex lattices and in-line holography.
Petersen, Timothy C; Bishop, Alexis I; Eastwood, Samuel A; Paganin, David M; Morgan, Kaye S; Morgan, Michael J
2016-02-01
We have developed a differential form of singularimetry, which utilizes phase vortices or intensity gradient singularities as topological fiducial markers in a structured illumination context. This approach analytically measures phase gradients imparted by refracting specimens, yielding quantitative information that is both local and deterministic. We have quantified our phase gradient experiments to demonstrate that lattices of wave field singularities can be used to detect subtle phase gradients imparted by a spherical specimen and fiber optic cylinders. PMID:26906802
NASA Technical Reports Server (NTRS)
Gross, L. W.
1976-01-01
The F-4E (CCV) wind tunnel model with closely coupled canard control surfaces was analyzed by means of a version of a vortex lattice program that included the effects of nonlinear leading edge or side edge vortex lift on as many as four individual planforms. The results were compared with experimental data from wind tunnel tests of a 5% scale model tested at a Mach number M = 0.6. They indicated that a nonlinear vortex lift developed on the side edges due to tip vortices, but did not appear to develop on the leading edges within the range of angles of attack that were studied. Instead, substantial leading edge thrust was developed on the lifting surfaces. A configuration buildup illustrated the mutual interference between the wing and control surfaces. On the configuration studied, addition of the wing increased the loading on the canard, but the additional load on the canard due to adding the stabilator was small.
NASA Technical Reports Server (NTRS)
Nguyen, Nhan; Ting, Eric; Nguyen, Daniel; Dao, Tung; Trinh, Khanh
2013-01-01
This paper presents a coupled vortex-lattice flight dynamic model with an aeroelastic finite-element model to predict dynamic characteristics of a flexible wing transport aircraft. The aircraft model is based on NASA Generic Transport Model (GTM) with representative mass and stiffness properties to achieve a wing tip deflection about twice that of a conventional transport aircraft (10% versus 5%). This flexible wing transport aircraft is referred to as an Elastically Shaped Aircraft Concept (ESAC) which is equipped with a Variable Camber Continuous Trailing Edge Flap (VCCTEF) system for active wing shaping control for drag reduction. A vortex-lattice aerodynamic model of the ESAC is developed and is coupled with an aeroelastic finite-element model via an automated geometry modeler. This coupled model is used to compute static and dynamic aeroelastic solutions. The deflection information from the finite-element model and the vortex-lattice model is used to compute unsteady contributions to the aerodynamic force and moment coefficients. A coupled aeroelastic-longitudinal flight dynamic model is developed by coupling the finite-element model with the rigid-body flight dynamic model of the GTM.
NASA Astrophysics Data System (ADS)
Shaidiuk, V.; Ammor, L.; Ruyter, A.
From the I-V characteristics for as-grown and irradiated Bi2Sr2CaCu2O8+δ single crystals at T=5K (i.e. T → 0) in a magnetic field applied parallel to c axis, we have seen two types of vortex dynamics above the depinning threshold, depending on the vortex-vortex interaction strength (λab/a0). For the as-grown sample, at a low field, the I-V curves show steps that clearly indicate a "fingerprint phenomenon" since they reflex the current dependence of the differential resistance rd(I). This can be ascribed to vortices flowing through uncorrelated channels for the highly defective lattice. As field sufficiently increase, these peaks merge to become broader ones indicating a crossover from filament type to braid river type. In contrast, in the irradiated sample, the pinning is found to be individual at low fields and collective when the vortex-vortex interactions are involved.
Effect of magnetic impurities on the vortex lattice properties in NbSe{sub 2} single crystals.
Iavarone, M.; Di Capua, R.; Karapetrov, G.; Koshelev, A. E.; Rosenmann, D.; Claus, H.; Malliakas, C. D.; Kanatzidis, M. G.; Nishizaki, T.; Kobayashi, N.; Materials Science Division; Univ. degli Studi del Molise; CNR-INFM Coherentia; Northwestern Univ.; Tohoku Univ.
2008-11-01
We report a pronounced peak effect in the magnetization of Co{sub x}NbSe{sub 2} single crystals with critical temperatures T{sub c} ranging between 7.1 and 5.0 K, and Mn{sub x}NbSe{sub 2} single crystals with critical temperatures down to 3.4 K. We correlate the peak effect in magnetization with the structure of the vortex lattice across the peak-effect region using scanning-tunneling microscopy. Magnetization measurements show that the amplitude of the peak effect in the case of Co{sub x}NbSe{sub 2} exhibits a nonmonotonic behavior as a function of the Co content, reaching a maximum for concentration of Co of about 0.4 at. % (corresponding to a T{sub c} of 5.7 K) and after that gradually decreasing in amplitude with the increase in the Co content. The normalized value of the peak position H{sub p}/H{sub c2} has weak dependence on Co concentration. In the case of Mn{sub x}NbSe{sub 2} the features of the peak effect as a function of the Mn content are different and they can be understood in terms of strong pinning.
History Dependence of the Vortex Lattice Rotation in the B-phase of UPt3 with H ∥ c
NASA Astrophysics Data System (ADS)
Avers, K. E.; Eskildsen, M. R.; Halperin, W. P.; Gannon, W. J.; Gavilano, J. L.; Nagy, G.; Gasser, U.
The unconventional superconductor UPt3 is widely believed to be a triplet superconductor, where the low temperature superconducting B-phase is a chiral state. We have performed small angle neutron scattering (SANS) from the vortex lattice (VL) in UPt3 at the Paul Scherrer Institute with the magnetic field parallel to the hexagonal c-axis in the 0.5 T to 0.9 T range. The diffraction pattern of the VL rotates away from a high symmetry direction producing two domains of different orientation. Our field dependent measurements show a subtle magnetic field history dependence of this orientation; VLs prepared with the magnetic field parallel or anti-parallel with respect to the angular momentum from the circulating screening currents show different field-history dependence. These results suggest a coupling of a chiral superconducting order parameter with the applied magnetic field. US DOE, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Awards DE-FG02-10ER46783 (University of Notre Dame; neutron scattering) and DE-FG02-05ER46248 (Northwestern University; crystal growth, characterization, neutron.
NASA Technical Reports Server (NTRS)
Ting, Eric; Nguyen, Nhan; Trinh, Khanh
2014-01-01
This paper presents a static aeroelastic model and longitudinal trim model for the analysis of a flexible wing transport aircraft. The static aeroelastic model is built using a structural model based on finite-element modeling and coupled to an aerodynamic model that uses vortex-lattice solution. An automatic geometry generation tool is used to close the loop between the structural and aerodynamic models. The aeroelastic model is extended for the development of a three degree-of-freedom longitudinal trim model for an aircraft with flexible wings. The resulting flexible aircraft longitudinal trim model is used to simultaneously compute the static aeroelastic shape for the aircraft model and the longitudinal state inputs to maintain an aircraft trim state. The framework is applied to an aircraft model based on the NASA Generic Transport Model (GTM) with wing structures allowed to flexibly deformed referred to as the Elastically Shaped Aircraft Concept (ESAC). The ESAC wing mass and stiffness properties are based on a baseline "stiff" values representative of current generation transport aircraft.
SANS study of vortex lattice structural transition in optimally doped (Ba1-x K x )Fe2As2.
Demirdiş, S; van der Beek, C J; Mühlbauer, S; Su, Y; Wolf, Th
2016-10-26
Small-angle neutron scattering on high quality single crystalline Ba1-x K x Fe2As2 reveals the transition from a low-field vortex solid phase with orientational order to a vortex polycrystal at high magnetic field. The vortex order-disorder transition is correlated with the second-peak feature in isothermal hysteresis loops, and is interpreted in terms of the generation of supplementary vortex solid dislocations. The sharp drop of the structure factor above the second peak field is explained by the dynamics of freezing of the vortex ensemble in the high field phase. PMID:27541966
NASA Astrophysics Data System (ADS)
Hankin, D.; Graham, J. M. R.
2014-12-01
An unsteady formulation of the vortex lattice method, VLM, is presented that uses a force- free representation of the wake behind a horizontal axis wind turbine, HAWT, to calculate the aerodynamic loading on a turbine operating in the wake of an upstream rotor. A Cartesian velocity grid is superimposed over the computational domain to facilitate the representation of the atmospheric turbulence surrounding the turbine and wind shear. The wake of an upstream rotor is modelled using two methods: a mean velocity deficit with superimposed turbulence, based on experimental observations, and a purely numeric periodic boundary condition. Both methods are treated as frozen and propagated with the velocity grid. Measurements of the mean thrust and blade root bending moment on a three bladed horizontal axis rotor modelling a 5 MW HAWT at 1:250 scale were carried out in a wind tunnel. Comparisons are made between operation in uniform flow and in the wake of a similarly loaded rotor approximately 6.5 diameters upstream. The measurements were used to validate the output from the VLM simulations, assuming a completely rigid rotor. The trends in the simulation thrust predictions are found to compare well with the uniform flow case, except at low tip speed ratios where there are losses due to stall which are yet to be included in the model. The simple wake model predicts the mean deficit, whilst the periodic boundary condition captures more of the frequency content of the loading in an upstream wake. However, all the thrust loads are over-predicted. The simulation results severely overestimate the bending moment, which needs addressing. However, the reduction in bending due to the simple wake model is found to reflect the experimental data reasonably well.
Kitaev anisotropy induces mesoscopic Z2 vortex crystals in frustrated hexagonal antiferromagnets
NASA Astrophysics Data System (ADS)
Rousochatzakis, Ioannis; Rössler, Ulrich K.; van den Brink, Jeroen; Daghofer, Maria
2016-03-01
The triangular-lattice Heisenberg antiferromagnet (HAF) is known to carry topological Z2 vortex excitations which form a gas at finite temperatures. Here we show that the spin-orbit interaction, introduced via a Kitaev term in the exchange Hamiltonian, condenses these vortices into a triangular Z2 vortex crystal at zero temperature. The cores of the Z2 vortices show abrupt, soliton-like magnetization modulations and arise by a special intertwining of three honeycomb superstructures of ferromagnetic domains, one for each of the three sublattices of the 120∘ state of the pure HAF. This is an example of a nucleation transition, analogous to the spontaneous formation of magnetic domains, Abrikosov vortices in type-II superconductors, blue phases in cholesteric liquid crystals, and skyrmions in chiral helimagnets. As the mechanism relies on the interplay of geometric frustration and spin-orbital anisotropies, such vortex mesophases can materialize as a ground state property in spin-orbit coupled correlated systems with nearly hexagonal topology, as in triangular or strongly frustrated honeycomb iridates.
Dynamic signatures of driven vortex motion.
Crabtree, G. W.; Kwok, W. K.; Lopez, D.; Olsson, R. J.; Paulius, L. M.; Petrean, A. M.; Safar, H.
1999-09-16
We probe the dynamic nature of driven vortex motion in superconductors with a new type of transport experiment. An inhomogeneous Lorentz driving force is applied to the sample, inducing vortex velocity gradients that distinguish the hydrodynamic motion of the vortex liquid from the elastic and-plastic motion of the vortex solid. We observe elastic depinning of the vortex lattice at the critical current, and shear induced plastic slip of the lattice at high Lorentz force gradients.
NASA Astrophysics Data System (ADS)
Kajzer, A.; Pozorski, J.; Szewc, K.
2014-08-01
In the paper we present Large-eddy simulation (LES) results of 3D Taylor- Green vortex obtained by the three different computational approaches: Smoothed Particle Hydrodynamics (SPH), Lattice Boltzmann Method (LBM) and Finite Volume Method (FVM). The Smagorinsky model was chosen as a subgrid-scale closure in LES for all considered methods and a selection of spatial resolutions have been investigated. The SPH and LBM computations have been carried out with the use of the in-house codes executed on GPU and compared, for validation purposes, with the FVM results obtained using the open-source CFD software OpenFOAM. A comparative study in terms of one-point statistics and turbulent energy spectra shows a good agreement of LES results for all methods. An analysis of the GPU code efficiency and implementation difficulties has been made. It is shown that both SPH and LBM may offer a significant advantage over mesh-based CFD methods.
Aegerter, C.M.; Hofer, J.; Savic, I.M.; Keller, H.; Lee, S.L.; Ager, C.; Lloyd, S.H.; Forgan, E.M.
1998-01-01
Using the techniques of muon spin rotation and torque magnetometry, we investigate the crossover field B{sub cr} in Bi{sub 2.15}Sr{sub 1.85}Ca{sub 1}Cu{sub 2}O{sub 8+{delta}} at which the vortex lattice becomes disordered along the field direction. It is found that B{sub cr} scales as the projection of the applied field along the perpendicular to the superconducting planes. This has the implication that a field large enough to give a disordered lattice when applied perpendicular to the planes, can give a well-ordered vortex-line lattice for angles of the field to the c axis greater than a critical value. {copyright} {ital 1998} {ital The American Physical Society}
Mathematical aspects of vortex dynamics; Proceedings of the Workshop, Leesburg, VA, Apr. 25-27, 1988
Caflisch, R.E.
1989-01-01
Various papers on the mathematical aspects of vortex dynamics are presented. Individual topics addressed include: mathematical analysis of vortex dynamics, improved vortex methods for three-dimensional flows, the relation between thin vortex layer and vortex sheets, computations of broadband instabilities in a class of closed-streamline flows, vortex-sheet dynamics and hyperfunction theory, free surface vortex method with weak viscous effects, iterative method for computing steady vortex flow systems, invariant measures for the two-dimensional Euler flow, similarity flows containing two-branched vortex sheets, strain-induced vortex stripping, convergence of the vortex method for vortex sheets, boundary conditions and deterministic vortex methods for the Navier-Stokes equations, vorticity creation boundary conditions, vortex dynamics of stratified flows, vortex breakdown, numerical studies of vortex reconnection, vortex lattices in theory and practice, dynamics of vortex structures in the wall region of a turbulent boundary layer, and energy of a vortex lattice configuration.
NASA Astrophysics Data System (ADS)
Ohlin, Kjell; Berggren, Karl Fredrik
2016-07-01
Faraday first characterised the behaviour of a fluid in a container subjected to vertical periodic oscillations. His study pertaining to hydrodynamic instability, the ‘Faraday instability’, has catalysed a myriad of experimental, theoretical, and numerical studies shedding light on the mechanisms responsible for the transition of a system at rest to a new state of well-ordered vibrational patterns at fixed frequencies. Here we study dual strata in a shallow vessel containing distilled water and high-viscosity lubrication oil on top of it. At elevated driving power, beyond the Faraday instability, the top stratum is found to ‘freeze’ into a rigid pattern with maxima and minima. At the same time there is a dynamic crossover into a new state in the form of a lattice of recirculating vortices in the lower layer containing the water. Instrumentation and the physics behind are analysed in a phenomenological way together with a basic heuristic modelling of the wave field. The study, which is based on relatively low-budget equipment, stems from related art projects that have evolved over the years. The study is of value within basic research as well as in education, especially as more advanced collective project work in e.g. engineering physics, where it invites further studies of pattern formation, the emergence of vortex lattices and complexity.
Induced vacuum current and magnetic field in the background of a vortex
NASA Astrophysics Data System (ADS)
Gorkavenko, Volodymyr M.; Ivanchenko, Iryna V.; Sitenko, Yurii A.
2016-02-01
A topological defect in the form of the Abrikosov-Nielsen-Olesen vortex is considered as a gauge-flux-carrying tube that is impenetrable for quantum matter. Charged scalar matter field is quantized in the vortex background with the perfectly reflecting (Dirichlet) boundary condition imposed at the side surface of the vortex. We show that a current circulating around the vortex and a magnetic field directed along the vortex are induced in the vacuum, if the Compton wavelength of the matter field exceeds considerably the transverse size of the vortex. The vacuum current and magnetic field are periodic in the value of the gauge flux of the vortex, providing a quantum-field-theoretical manifestation of the Aharonov-Bohm effect. The total flux of the induced vacuum magnetic field attains notable finite values even for the Compton wavelength of the matter field exceeding the transverse size of the vortex by just three orders of magnitude.
Neutron Scattering Studies of Vortex Matter in Type-II Superconductors
Xinsheng Ling
2012-02-02
The proposed program is an experimental study of the fundamental properties of Abrikosov vortex matter in type-II superconductors. Most superconducting materials used in applications such as MRI are type II and their transport properties are determined by the interplay between random pinning, interaction and thermal fluctuation effects in the vortex state. Given the technological importance of these materials, a fundamental understanding of the vortex matter is necessary. The vortex lines in type-II superconductors also form a useful model system for fundamental studies of a number of important issues in condensed matter physics, such as the presence of a symmetry-breaking phase transition in the presence of random pinning. Recent advances in neutron scattering facilities such as the major upgrade of the NIST cold source and the Spallation Neutron Source are providing unprecedented opportunities in addressing some of the longstanding issues in vortex physics. The core component of the proposed program is to use small angle neutron scattering and Bitter decoration experiments to provide the most stringent test of the Bragg glass theory by measuring the structure factor in both the real and reciprocal spaces. The proposed experiments include a neutron reflectometry experiment to measure the precise Q-dependence of the structure factor of the vortex lattice in the Bragg glass state. A second set of SANS experiments will be on a shear-strained Nb single crystal for testing a recently proposed theory of the stability of Bragg glass. The objective is to artificially create a set of parallel grain boundaries into a Nb single crystal and use SANS to measure the vortex matter diffraction pattern as a function of the changing angle between the applied magnetic field to the grain boundaries. The intrinsic merits of the proposed work are a new fundamental understanding of type-II superconductors on which superconducting technology is based, and a firm understanding of phases
Ferrando, Albert; Garcia-March, Miguel-Angel
2005-09-16
Using group theory arguments and numerical simulations, we demonstrate the possibility of changing the vorticity or topological charge of an individual vortex by means of the action of a system possessing a discrete rotational symmetry of finite order. We establish on theoretical grounds a 'transmutation pass rule' determining the conditions for this phenomenon to occur and numerically analyze it in the context of two-dimensional optical lattices. An analogous approach is applicable to the problems of Bose-Einstein condensates in periodic potentials.
NASA Astrophysics Data System (ADS)
Yepez, J.; Vahala, G.; Vahala, L.
2009-04-01
Presented is a type-II quantum algorithm for superfluid dynamics, used to numerically predict solutions of the GP equation for a complex scalar field (spinless bosons) in φ4 theory. The GP equation is a long wavelength effective field theory of a microscopic quantum lattice gas with nonlinear state reduction. The quantum lattice gas algorithm for modeling the dynamics of the one-body BEC state in 3+1 dimensions is presented. To demonstrate the method's strength as a computational physics tool, a difficult situation of filamentary singularities is simulated, the dynamics of solitary vortex-antivortex pairs, which are a basic building block of morphologies of quantum turbulence.
Tilt-modulus enhancement of the vortex lattice in the layered superconductor 2 H -NbSe sub 2
Koorevaar, P.; Aarts, J.; Berghuis, P.; Kes, P.H. )
1990-07-01
The field dependence of the pinning force has been studied in thin single crystals of the layered superconductor 2{ital H}-NbSe{sub 2} in fields directed perpendicular to the layers. At high fields a peak effect is observed which sets in at about {ital B}{sub co}{approx}0.8{ital B}{sub {ital c}2}. Below this field the pinning force agrees well with the theory of two-dimensional collective pinning. The onset of the peak is triggered by the transition to three-dimensional flux-line lattice (FLL) disorder at the field {ital B}{sub co}. Comparison of the crossover field with the criterion set by the collective-pinning theory reveals that the tilt modulus of the FLL in a layered superconductor is considerably reduced. The reduction factor corresponds very well to recent theoretical predictions. These results are of importance for the prediction of depinning and flux-line lattice melting in all kinds of anisotropic superconductors.
NASA Technical Reports Server (NTRS)
Berry, John D.
1988-01-01
A method is described for the analysis of the unsteady, incompressible potential flow associated with a helicopter rotor and it's wake in forward flight. This method is particularly useful in low advance ratio flight due to the major contribution, in the near field, of the deformed wake. The rotor geometry is prescribed and the unsteady wake geometry is computed from the local flow perturbation velocities. The wake is modeled as a full vortex lattice. The rotor geometry is arbitrary and several rotor blades can be represented. The unsteady airloads on the rotor blades are computed in the presence of the deformed rotor wake by a time-stepping technique. Solution for the load distribution on the blade surfaces is found by prescribing boundary conditions in a reference system which rotates with the blade tips. Transformation tensors are used to describe the contribution of the wake in the inertial system to the rotor in the rotating reference system. The effects of blade cyclic pitch variation are computed using a rotation tensor. The deformation of the wake is computed in the inertial frame. The wake is started impulsively from rest, allowing a natural convection of the wake with time.
Vortex dynamics in anisotropic traps
McEndoo, S.; Busch, Th.
2010-07-15
We investigate the dynamics of linear vortex lattices in anisotropic traps in two dimensions and show that the interplay between the rotation and the anisotropy leads to a rich but highly regular dynamics.
User's manual for interfacing a leading edge, vortex rollup program with two linear panel methods
NASA Technical Reports Server (NTRS)
Desilva, B. M. E.; Medan, R. T.
1979-01-01
Sufficient instructions are provided for interfacing the Mangler-Smith, leading edge vortex rollup program with a vortex lattice (POTFAN) method and an advanced higher order, singularity linear analysis for computing the vortex effects for simple canard wing combinations.
Electronic structure of multiquantum giant vortex states in mesoscopic superconducting disks
Tanaka, Kaori; Robel, István; Jankó, Boldizsár
2002-01-01
We report self-consistent calculations of the microscopic electronic structure of the so-called giant vortex states. These multiquantum vortex states, detected by recent magnetization measurements on submicron disks, are qualitatively different from the Abrikosov vortices in the bulk. We find that, in addition to multiple branches of bound states in the core region, the local tunneling density of states exhibits Tomasch oscillations caused by the single-particle interference arising from quantum confinement. These features should be directly observable by scanning tunneling spectroscopy. PMID:16578872
Cristiano, R.; Frunzio, L.; Pagano, S.; Palmieri, V.G.; Lisitskii, M.P.
1997-11-01
We report on a new experimental approach to the size estimation of the hot spot induced by ionizing particles in a Josephson tunnel junction. Here, in contrast to the case of a superconducting strip, it is possible to investigate the hot spot dynamics in absence of effects due to the heating induced by the bias current. The reported experiment is based on the motion of Abrikosov vortices, trapped in the thin films constituting the junction electrodes, under 5.6 MeV {alpha}-particle irradiation. The fast time evolution of a hot spot, combined with the presence of Abrikosov vortices, produces a change of the static magnetic field in the junction area and thus a change of the critical current value, I{sub c}. Measurements of I{sub c} during the {alpha}-particle irradiation and in presence of trapped Abrikosov vortices allow to determine the rate of appearance of those I{sub c} changes. The behavior of the average appearance rate as function of the Abrikosov vortices density provides a direct determination of the maximum hot spot area. The experiment is performed on a high quality Nb/Al{endash}AlO{sub x}/Nb junction of circular geometry and with {open_quotes}small{close_quotes} dimensions with respect to the Josephson penetration depth. A value of 4.7{plus_minus}1.2{mu}m{sup 2} is found for the maximum hot spot area. {copyright} {ital 1997 American Institute of Physics.}
Quantum vortices in optical lattices
Vignolo, P.; Fazio, R.; Tosi, M. P.
2007-08-15
A vortex in a superfluid gas inside an optical lattice can behave as a massive particle moving in a periodic potential and exhibiting quantum properties. In this paper we discuss these properties and show that the excitation of vortex dynamics in a two-dimensional lattice can lead to striking measurable changes in its dynamic response. It would be possible by means of Bragg spectroscopy to carry out the first direct measurement of the effective vortex mass. In addition, the experiments proposed here provide an alternative way to study the pinning to the underlying lattice and the dissipative damping.
Experimental evidence for flux-lattice melting. [in high-Tc superconductors
NASA Technical Reports Server (NTRS)
Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.
1991-01-01
A low-frequency torsional oscillator has been used to search for flux-lattice melting in an untwinned single crystal of YBa2Cu3O(7-delta). The damping of the oscillator was measured as a function of temperature, for applied magnetic fields in the range H = 0.1-2.3 T. A remarkably sharp damping peak has been located. It is suggested that the temperature of the peak corresponds to the melting point of the Abrikosov flux lattice.
Rakhmanov, A L; Savel'ev, Sergey; Kusmartsev, F V
2008-11-01
We describe the decomposition of Abrikosov vortices into decoupled pancake vortices in superconductors having both electron and hole charge carriers. We estimate the critical current of such a decomposition, at which a superconducting-normal state transition occurs, and find that it is very sensitive to the magnetic field and temperature. The effect can be observed in recently synthesized self-doped high-Tc layered superconductors with electrons and holes coexisting in different Cu-O planes and in artificial p-n superconductor heterostructures. The sensitivity of the critical current to a magnetic field may be used for sensors and detectors of a magnetic field, which can be built up from the superconductor heterostructures. PMID:19113298
Non-Vortex Topological Solitons of the [InlineMediaObject not available: see fulltext.] Gauge Model
NASA Astrophysics Data System (ADS)
Afanas'ev, K. V.; Gauzshtein, V. V.; Loginov, A. Yu.
2016-06-01
A (2+1)-dimensional [InlineMediaObject not available: see fulltext.] gauge model is investigated. The presence of additional local U(1) symmetry, not associated with a physical gauge field, leads to the existence in the given model of two-dimensional non-vortex topological solitons carrying unquantized magnetic flux. Topological solitons of the given type were found numerically for fixed values of the model parameters. Analytical calculations of some properties of non-vortex topological solitons were performed. Universal dependences of the energy and magnetic flux of a non-vortex topological soliton on a dimensionless combination of parameters of the [InlineMediaObject not available: see fulltext.] gauge model were obtained numerically. A comparative analysis of the properties of a non-vortex topological soliton and an Abrikosov-Nielsen-Olesen classical vortex is provided.
Cho, Inyong; Lee, Youngone
2009-01-15
We investigate vortex configurations with the 'vulcanization' term inspired by the renormalization of {phi}{sub *}{sup 4} theory in the canonical {theta}-deformed noncommutativity. We focus on the classical limit of the theory described by a single parameter which is the ratio of the vulcanization and the noncommutativity parameters. We perform numerical calculations and find that nontopological vortex solutions exist as well as Q-ball type solutions, but topological vortex solutions are not admitted.
NASA Astrophysics Data System (ADS)
Cho, Inyong; Lee, Youngone
2009-01-01
We investigate vortex configurations with the “vulcanization” term inspired by the renormalization of ϕ⋆4 theory in the canonical θ-deformed noncommutativity. We focus on the classical limit of the theory described by a single parameter which is the ratio of the vulcanization and the noncommutativity parameters. We perform numerical calculations and find that nontopological vortex solutions exist as well as Q-ball type solutions, but topological vortex solutions are not admitted.
Dynamic visualization of nanoscale vortex orbits.
Timmermans, Matias; Samuely, Tomas; Raes, Bart; Van de Vondel, Joris; Moshchalkov, Victor V
2014-03-25
Due to the atomic-scale resolution, scanning tunneling microscopy is an ideal technique to observe the smallest objects. Nevertheless, it suffers from very long capturing times in order to investigate dynamic processes at the nanoscale. We address this issue, for vortex matter in NbSe2, by driving the vortices using an ac magnetic field and probing the induced periodic tunnel current modulations. Our results reveal different dynamical modes of the driven vortex lattices. In addition, by recording and synchronizing the time evolution of the tunneling current at each pixel, we visualize the overall dynamics of the vortex lattice with submillisecond time resolution and subnanometer spatial resolution. PMID:24460428
Vortex induced strain effects in anisotropic superconductors
Miranovic, P.; Dobrosavljevic-Grujic, L.; Kogan, V.G.
1996-12-31
Strain in a superconductor, produced by the normal vortex core, can affect both static and dynamic properties of vortices. It causes an additional vortex-vortex interaction which is long-ranged ({approximately} 1/r{sup 2}) as compared with finite but much stronger London interaction in the fields far below H{sub c2}. The energy of this magneto-elastic interaction is calculated within London model. The role of strain effects in forming vortex lattice structure is demonstrated for YBa{sub 2}Cu{sub 3}O{sub 7}.
NASA Astrophysics Data System (ADS)
Flis, V. S.; Kalenyuk, A. A.; Kasatkin, A. L.; Moskalyuk, V. O.; Rebikov, A. I.; Svechnikov, V. L.; Tret'yachenko, K. G.; Pan, V. M.
2010-01-01
This paper presents the results of a comprehensive study of the relationship of the structural and electrodynamic characteristics of quasi-single-crystal films of the HTSC cuprate YBa2Cu3O7-δ (YBCO) with various concentrations (several mass percent) of nanosize inclusions of the perovskitelike phase of BaZrO3 (BZO). High-resolution electron microscopy is used to investigate the nanostructure of the fabricated films and to determine the main types of defects that cause strong pinning of Abrikosov vortices and, accordingly, large critical current densities. The results of theoretically modelling the genesis of the defect nanostructure that appears in such films and its influence on the critical current are presented. The magnetic and transport properties of HTSC films made from YBCO(BZO) have been experimentally studied. The temperature, magnetic-field, and magnetic-orientation dependences of the critical current density of the test films are found. The results of an experimental investigation of the high-frequency properties of YBZO(BZO) films—the surface microwave impedance of the films in the linear and nonlinear regimes—are also given. The experimental results are discussed, and the influence of the nanostructure of the impurity phase on the electrodynamic characteristics of the HTSC films is analyzed.
Programmable lattices of optical vortices in nematic liquid crystal
NASA Astrophysics Data System (ADS)
Barboza, R.; Assanto, G.; Bortolozzo, U.; Clerc, M. G.; Residori, S.; Vidal-Henriquez, E.
2015-09-01
Using self-induced vortex-like defects in the nematic liquid crystal layer of a light valve with photo-sensible wall, we demonstrate the realization of programable optical vortices lattices with arbitrary configuration in space. On each lattice site, every matter vortex acts as a photonic spin-to-orbital momentum coupler and an array of circularly polarized input beams is converted into an output array of vortex beams with topological charges consistent with the vortex matter lattice. The vortex arrangements are explained the basis of light-induced matter defects and topological rules.
Vortex methods and vortex statistics
Chorin, A.J.
1993-05-01
Vortex methods originated from the observation that in incompressible, inviscid, isentropic flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus if the vorticity is known at time t = 0, one can deduce the flow at a later time by simply following it around. In this narrow context, a vortex method is a numerical method that makes use of this observation. Even more generally, the analysis of vortex methods leads, to problems that are closely related to problems in quantum physics and field theory, as well as in harmonic analysis. A broad enough definition of vortex methods ends up by encompassing much of science. Even the purely computational aspects of vortex methods encompass a range of ideas for which vorticity may not be the best unifying theme. The author restricts himself in these lectures to a special class of numerical vortex methods, those that are based on a Lagrangian transport of vorticity in hydrodynamics by smoothed particles (``blobs``) and those whose understanding contributes to the understanding of blob methods. Vortex methods for inviscid flow lead to systems of ordinary differential equations that can be readily clothed in Hamiltonian form, both in three and two space dimensions, and they can preserve exactly a number of invariants of the Euler equations, including topological invariants. Their viscous versions resemble Langevin equations. As a result, they provide a very useful cartoon of statistical hydrodynamics, i.e., of turbulence, one that can to some extent be analyzed analytically and more importantly, explored numerically, with important implications also for superfluids, superconductors, and even polymers. In the authors view, vortex ``blob`` methods provide the most promising path to the understanding of these phenomena.
Electromagnetic Radiation from Vortex Flow in Type-II Superconductors
Bulaevskii, L. N.; Chudnovsky, E. M.
2006-11-10
We show that a moving vortex lattice, as it comes to a crystal edge, radiates into a free space the harmonics of the washboard frequency, {omega}{sub 0}=2{pi}v/a, up to a superconducting gap, {delta}/({Dirac_h}/2{pi}). Here v is the velocity of the vortex lattice and a is the intervortex spacing. We compute radiation power and show that this effect can be used for the generation of terahertz radiation and for characterization of moving vortex lattices.
Leapfrogging of multiple coaxial viscous vortex rings
Cheng, M. Lou, J.; Lim, T. T.
2015-03-15
A recent theoretical study [Borisov, Kilin, and Mamaev, “The dynamics of vortex rings: Leapfrogging, choreographies and the stability problem,” Regular Chaotic Dyn. 18, 33 (2013); Borisov et al., “The dynamics of vortex rings: Leapfrogging in an ideal and viscous fluid,” Fluid Dyn. Res. 46, 031415 (2014)] shows that when three coaxial vortex rings travel in the same direction in an incompressible ideal fluid, each of the vortex rings alternately slips through (or leapfrogs) the other two ahead. Here, we use a lattice Boltzmann method to simulate viscous vortex rings with an identical initial circulation, radius, and separation distance with the aim of studying how viscous effect influences the outcomes of the leapfrogging process. For the case of two identical vortex rings, our computation shows that leapfrogging can be achieved only under certain favorable conditions, which depend on Reynolds number, vortex core size, and initial separation distance between the two rings. For the case of three coaxial vortex rings, the result differs from the inviscid model and shows that the second vortex ring always slips through the leading ring first, followed by the third ring slipping through the other two ahead. A simple physical model is proposed to explain the observed behavior.
Nonlinear electrodynamics of vortex matter in hard superconductors (Review)
NASA Astrophysics Data System (ADS)
Voloshin, I. F.; Fisher, L. M.; Yampol'Skiĭ, V. A.
2010-01-01
Nontrivial electrodynamic properties of vortex matter, which are due to a specific nonlinearity of the material equations, in hard superconductors are discussed: collapse of the transport current and the static magnetization of superconductors by an external orthogonal ac magnetic field; appearance of jumps in the time dependence of the electric field at the boundary of a sample as a result of nonlinear interaction of waves having different frequencies; specific staged penetration of an electromagnetic field into anisotropic superconductors. Nonlocal effects resulting in a large modification of nonlinear phenomena are also examined. Special attention is given to a discussion of the unique phenomenon of macroturbulent instability, associated with the flow of Abrikosov vortices, in hard superconductors. Most results presented are based on original experimental and theoretical investigations performed with the participation of the present authors.
Atmospheric Science Data Center
2013-06-26
... within the cloud layer downwind of the obstacle. These turbulence patterns are known as von Karman vortex streets. In these images ... was the first to derive the conditions under which these turbulence patterns occur. von Karman was a professor of aeronautics at the ...
NASA Astrophysics Data System (ADS)
Mills, Shaun A.; Wisser, Jacob J.; Shen, Chenyi; Xu, Zhuan; Liu, Ying
2016-06-01
Nanowires of two-dimensional (2D) crystals of type-II superconductor NbSe2 prepared by electron-beam lithography were studied, focusing on the effect of the motion of Abrikosov vortices. We present magnetoresistance measurements on these nanowires and show features related to vortex crossing, trapping, and pinning. The vortex crossing rate was found to vary nonmonotonically with the applied field, which results in nonmonotonic magnetoresistance variations in agreement with theoretical calculations in the London approximation. Above the lower critical field Hc 1 the crossing rate is also influenced by vortices trapped by sample boundaries or pinning centers, leading to sample-specific magnetoresistance patterns. We show that the local pinning potential can be modified by intentionally introducing surface adsorbates, making the magnetoresistance pattern a "magnetofingerprint" of the sample-specific configuration of vortex pinning centers in a 2D crystal superconducting nanowire.
NASA Astrophysics Data System (ADS)
Mills, Shaun A.; Shen, Chenyi; Xu, Zhuan; Liu, Ying
2015-10-01
Numerical calculations on a mesoscopic ring of a type-II superconductor in the London limit suggest that an Abrikosov vortex can be trapped in such a structure above a critical magnetic field and generate a phase shift in the magnetoresistance oscillations. We prepared submicron-sized superconducting loops of single-crystal, type-II superconductor NbSeSUB>2 and measured magnetoresistance oscillations resulting from vortices crossing the loops. The free-energy barrier for vortex crossing determines the crossing rate and is periodically modulated by the external magnetic flux threading the loop. We demonstrated experimentally that the crossing of vortices can be directed at a pair of constrictions in the loop, leading to more pronounced magnetoresistance oscillations than those in a uniform ring. The vortex trapping in both a simple ring and a ring featuring two constrictions was found to result in a phase shift in the magnetoresistance oscillations as predicted in the numerical calculations. The controlled crossing and trapping of vortices demonstrated in our NbSeSUB>2 devices provide a starting point for the manipulation of individual Abrikosov vortices, which is useful for future technologies.
Optimum lattice arrangement developed from a rigorous analytical basis
NASA Technical Reports Server (NTRS)
Deyoung, J.
1976-01-01
The spanwise vortex-lattice arrangement is mathematically established by lattice solutions of the slender wing which are shown to be analogous to the chordwise vortex-lattice thin wing solution. Solutions for any number N of panels wing theory lift and induced drag and thin wing theory lift and moment are predicted exactly. As N approaches infinity, the slender wing elliptic spanwise loading and thin wing cotangent chordwise loading are predicted, which proves there is mathematical convergence of the vortex-lattice method to the exact answer. Based on this planform spanwise lattice arrangement, an A-vortex-lattice spanwise system is developed for an arbitrary aspect ratio A. This A-lattice has the optimum characteristic of predicting lift accurately for any value of N.
Revisiting the vortex-core tunnelling spectroscopy in YBa2Cu3O7-δ
NASA Astrophysics Data System (ADS)
Bruér, Jens; Maggio-Aprile, Ivan; Jenkins, Nathan; Ristić, Zoran; Erb, Andreas; Berthod, Christophe; Fischer, Øystein; Renner, Christoph
2016-03-01
The observation by scanning tunnelling spectroscopy of Abrikosov vortex cores in the high-temperature superconductor YBa2Cu3O7-δ (Y123) has revealed a robust pair of electron-hole symmetric states at finite subgap energy. Their interpretation remains an open question because theory predicts a different signature in the vortex cores, characterized by a strong zero-bias conductance peak. Here, we present scanning tunnelling spectroscopy data on very homogeneous Y123 at 0.4 K revealing that the subgap features do not belong to vortices: they are actually observed everywhere along the surface with high spatial and energy reproducibility, even in the absence of magnetic field. Detailed analysis and modelling show that these states remain unpaired in the superconducting phase and belong to an incoherent channel, which contributes to the tunnelling signal in parallel with the superconducting density of states.
Hexatic vortex glass in disordered superconductors
Chudnovsky, E.M. )
1989-12-01
It is shown that interaction of the flux-line lattice with randomly arranged pinning centers should destroy the long-range positional order in the lattice, but not the long-range orientational order. A new phase: hexatic vortex glass, is suggested for the mixed state of disordered, type-II superconductors. Relevance to amorphous and high-{ital T}{sub {ital c}} superconductors is discussed.
Confining bond rearrangement in the random center vortex model
NASA Astrophysics Data System (ADS)
Altarawneh, Derar; Höllwieser, Roman; Engelhardt, Michael
2016-03-01
We present static meson-meson and baryon-antibaryon potentials in Z (2 ) and Z (3 ) random center vortex models for the infrared sector of Yang-Mills theory, i.e., hypercubic lattice models of random vortex world surfaces. In particular, we calculate multiple Polyakov loop correlators corresponding to static meson-meson or baryon-antibaryon configurations in a center vortex background and observe that their expectation values follow the minimal area law, displaying bond rearrangement behavior, a characteristic expected for the confining dynamics of the strong interaction. The static meson-meson and baryon-antibaryon potentials are compared with theoretical predictions and lattice QCD simulations.
Fractionalized gapless quantum vortex liquids
NASA Astrophysics Data System (ADS)
Wang, Chong; Senthil, T.
2015-05-01
The standard theoretical approach to gapless spin liquid phases of two-dimensional frustrated quantum antiferromagnets invokes the concept of fermionic slave particles into which the spin fractionalizes. As an alternate we explore different kinds of gapless spin liquid phases in frustrated quantum magnets with X Y anisotropy where the vortex of the spin fractionalizes into gapless itinerant fermions. The resulting gapless fractionalized vortex liquid phases are studied within a slave particle framework that is dual to the usual one. We demonstrate the stability of some such phases and describe their properties. We give an explicit construction in an X Y -spin-1 system on triangular lattice, and interpret it as a critical phase in the vicinity of spin-nematic states.
Revisiting the vortex-core tunnelling spectroscopy in YBa2Cu3O7−δ
Bruér, Jens; Maggio-Aprile, Ivan; Jenkins, Nathan; Ristić, Zoran; Erb, Andreas; Berthod, Christophe; Fischer, Øystein; Renner, Christoph
2016-01-01
The observation by scanning tunnelling spectroscopy of Abrikosov vortex cores in the high-temperature superconductor YBa2Cu3O7−δ (Y123) has revealed a robust pair of electron-hole symmetric states at finite subgap energy. Their interpretation remains an open question because theory predicts a different signature in the vortex cores, characterized by a strong zero-bias conductance peak. Here, we present scanning tunnelling spectroscopy data on very homogeneous Y123 at 0.4 K revealing that the subgap features do not belong to vortices: they are actually observed everywhere along the surface with high spatial and energy reproducibility, even in the absence of magnetic field. Detailed analysis and modelling show that these states remain unpaired in the superconducting phase and belong to an incoherent channel, which contributes to the tunnelling signal in parallel with the superconducting density of states. PMID:27030516
Vortex Flow Aerodynamics, volume 1
NASA Technical Reports Server (NTRS)
Campbell, J. F. (Editor); Osborn, R. F. (Editor); Foughner, J. T., Jr. (Editor)
1986-01-01
Vortex modeling techniques and experimental studies of research configurations utilizing vortex flows are discussed. Also discussed are vortex flap investigations using generic and airplane research models and vortex flap theoretical analysis and design studies.
Vortex Flow Aerodynamics, volume 1
Campbell, J.F.; Osborn, R.F.; Foughner, J.T. Jr.
1986-07-01
Vortex modeling techniques and experimental studies of research configurations utilizing vortex flows are discussed. Also discussed are vortex flap investigations using generic and airplane research models and vortex flap theoretical analysis and design studies.
Sayko, G.V.; Bugaev, A.S.; Popkov, A.F.
1994-12-31
The authors consider vortex lattice interaction with transverse surface magnetoacoustic wave in high-{Tc} superconductor-ferrite structure. It has been found that the magnetoacoustic waves excited in the ferrite can be efficiently coupled with vortex structure in superconducting film. The nonlinear effect of vortex drift as well as the possibility of the wave amplification are discussed.
Critical Capacitance and Charge-Vortex Duality Near the Superfluid-to-Insulator Transition
NASA Astrophysics Data System (ADS)
Gazit, Snir; Podolsky, Daniel; Auerbach, Assa
2014-12-01
Using a generalized reciprocity relation between charge and vortex conductivities at complex frequencies in two space dimensions, we identify the capacitance in the insulating phase as a measure of vortex condensate stiffness. We compute the ratio of boson superfluid stiffness to vortex condensate stiffness at mirror points to be 0.21(1) for the relativistic O(2) model. The product of dynamical conductivities at mirror points is used as a quantitative measure of deviations from self-duality between charge and vortex theories. We propose the finite wave vector compressibility as an experimental measure of the vortex condensate stiffness for neutral lattice bosons.
Reconfigurable large-area magnetic vortex circulation patterns
NASA Astrophysics Data System (ADS)
Streubel, Robert; Kronast, Florian; Rößler, Ulrich K.; Schmidt, Oliver G.; Makarov, Denys
2015-09-01
Magnetic vortices in nanodots own a switchable circulation sense. These nontrivial magnetization configurations can be arranged into extended and interacting patterns. We have experimentally created large arrays of magnetically reconfigurable vortex patterns in nonplanar honeycomb lattices using particle lithography. Optimizing height asymmetry of the vertices and applying an in-plane magnetic field provide means to switch between homocircular and staggered vortex patterns with a potentially high impact on magnonics and spintronics relying on chiral noncollinear spin textures. To this end, exchange coupling of extended vortex lattices with an out-of-plane magnetized layer allows one to realize artificial skyrmionic core textures with controllable circulation and topological properties in extended exchange coupled honeycomb lattices that may pave the way towards magnetic memory and logic devices based on artificial skyrmions.
Quantum vortex dynamics in two-dimensional neutral superfluids
Wang, C.-C. Joseph; Duine, R. A.; MacDonald, A. H.
2010-01-15
We derive an effective action for the vortex-position degree of freedom in a superfluid by integrating out condensate phase- and density-fluctuation environmental modes. When the quantum dynamics of environmental fluctuations is neglected, we confirm the occurrence of the vortex Magnus force and obtain an expression for the vortex mass. We find that this adiabatic approximation is valid only when the superfluid droplet radius R, or the typical distance between vortices, is very much larger than the coherence length xi. We go beyond the adiabatic approximation numerically, accounting for the quantum dynamics of environmental modes and capturing their dissipative coupling to condensate dynamics. For the case of an optical-lattice superfluid, we demonstrate that vortex motion damping can be adjusted by tuning the ratio between the tunneling energy J and the on-site interaction energy U. We comment on the possibility of realizing vortex-Landau-level physics.
Monte Carlo simulation of two-dimensional flux-line-lattice melting
Kato, Y.; Nagaosa, N. )
1993-09-01
A Monte Carlo simulation of a two-dimensional flux-line-lattice (FLL) melting transition is presented. The internal energy, specific heat, Abrikosov ratio, and diffraction pattern of the magnitude [vert bar][psi]([ital x])[vert bar][sup 2] of the order-parameter field are calculated. By examining in detail the hysteresis, histogram, and relaxation profiles of the internal energy, the existence of a first-order phase transition is concluded. Below the transition temperature [ital t][sub [ital m
Superconducting vortex pinning with artificial magnetic nanostructures.
Velez, M.; Martin, J. I.; Villegas, J. E.; Hoffmann, A.; Gonzalez, E. M.; Vicent, J. L.; Schuller, I. K.; Univ. de Oviedo-CINN; Unite Mixte de Physique CNRS Univ. Paris-Sud; Univ.Complutense de Madrid; Univ. California at San Diego
2008-11-01
This review is dedicated to summarizing the recent research on vortex dynamics and pinning effects in superconducting films with artificial magnetic structures. The fabrication of hybrid superconducting/magnetic systems is presented together with the wide variety of properties that arise from the interaction between the superconducting vortex lattice and the artificial magnetic nanostructures. Specifically, we review the role that the most important parameters in the vortex dynamics of films with regular array of dots play. In particular, we discuss the phenomena that appear when the symmetry of a regular dot array is distorted from regularity towards complete disorder including rectangular, asymmetric, and aperiodic arrays. The interesting phenomena that appear include vortex-lattice reconfigurations, anisotropic dynamics, channeling, and guided motion as well as ratchet effects. The different regimes are summarized in a phase diagram indicating the transitions that take place as the characteristic distances of the array are modified respect to the superconducting coherence length. Future directions are sketched out indicating the vast open area of research in this field.
Three-dimensional vortex structures in a rotating dipolar Bose–Einstein condensate
NASA Astrophysics Data System (ADS)
Kishor Kumar, Ramavarmaraja; Sriraman, Thangarasu; Fabrelli, Henrique; Muruganandam, Paulsamy; Gammal, Arnaldo
2016-08-01
We study three-dimensional vortex lattice structures in purely dipolar Bose–Einstein condensate (BEC). By using the mean-field approximation, we obtain a stability diagram for the vortex states in purely dipolar BECs as a function of harmonic trap aspect ratio (λ) and dipole–dipole interaction strength (D) under rotation. Rotating the condensate within the unstable region leads to collapse while in the stable region furnishes stable vortex lattices of dipolar BECs. We analyse stable vortex lattice structures by solving the three-dimensional time-dependent Gross–Pitaevskii equation in imaginary time. Further, the stability of vortex states is examined by evolution in real-time. We also investigate the distribution of vortices in a fully anisotropic trap by increasing eccentricity of the external trapping potential. We observe the breaking up of the condensate in two parts with an equal number of vortices on each when the trap is sufficiently weak, and the rotation frequency is high.
Wave modes of collective vortex gyration in dipolar-coupled-dot-array magnonic crystals
Han, Dong-Soo; Vogel, Andreas; Jung, Hyunsung; Lee, Ki-Suk; Weigand, Markus; Stoll, Hermann; Schütz, Gisela; Fischer, Peter; Meier, Guido; Kim, Sang-Koog
2013-01-01
Lattice vibration modes are collective excitations in periodic arrays of atoms or molecules. These modes determine novel transport properties in solid crystals. Analogously, in periodical arrangements of magnetic vortex-state disks, collective vortex motions have been predicted. Here, we experimentally observe wave modes of collective vortex gyration in one-dimensional (1D) periodic arrays of magnetic disks using time-resolved scanning transmission x-ray microscopy. The observed modes are interpreted based on micromagnetic simulation and numerical calculation of coupled Thiele equations. Dispersion of the modes is found to be strongly affected by both vortex polarization and chirality ordering, as revealed by the explicit analytical form of 1D infinite arrays. A thorough understanding thereof is fundamental both for lattice vibrations and vortex dynamics, which we demonstrate for 1D magnonic crystals. Such magnetic disk arrays with vortex-state ordering, referred to as magnetic metastructure, offer potential implementation into information processing devices. PMID:23877284
Wave modes of collective vortex gyration in dipolar-coupled-dot-array magnonic crystals.
Han, Dong-Soo; Vogel, Andreas; Jung, Hyunsung; Lee, Ki-Suk; Weigand, Markus; Stoll, Hermann; Schütz, Gisela; Fischer, Peter; Meier, Guido; Kim, Sang-Koog
2013-01-01
Lattice vibration modes are collective excitations in periodic arrays of atoms or molecules. These modes determine novel transport properties in solid crystals. Analogously, in periodical arrangements of magnetic vortex-state disks, collective vortex motions have been predicted. Here, we experimentally observe wave modes of collective vortex gyration in one-dimensional (1D) periodic arrays of magnetic disks using time-resolved scanning transmission x-ray microscopy. The observed modes are interpreted based on micromagnetic simulation and numerical calculation of coupled Thiele equations. Dispersion of the modes is found to be strongly affected by both vortex polarization and chirality ordering, as revealed by the explicit analytical form of 1D infinite arrays. A thorough understanding thereof is fundamental both for lattice vibrations and vortex dynamics, which we demonstrate for 1D magnonic crystals. Such magnetic disk arrays with vortex-state ordering, referred to as magnetic metastructure, offer potential implementation into information processing devices. PMID:23877284
Propeller tip vortex interactions
NASA Technical Reports Server (NTRS)
Johnston, Robert T.; Sullivan, John P.
1990-01-01
Propeller wakes interacting with aircraft aerodynamic surfaces are a source of noise and vibration. For this reason, flow visualization work on the motion of the helical tip vortex over a wing and through the second stage of a counterrotation propeller (CRP) has been pursued. Initially, work was done on the motion of a propeller helix as it passes over the center of a 9.0 aspect ratio wing. The propeller tip vortex experiences significant spanwise displacements when passing across a lifting wing. A stationary propeller blade or stator was installed behind the rotating propeller to model the blade vortex interaction in a CRP. The resulting vortex interaction was found to depend on the relative vortex strengths and vortex sign.
Kim, P.; Yao, Z.; Lieber, C.M.
1996-12-01
The microscopic structure of the magnetic flux-line lattice (FLL) in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} superconductors was studied at temperatures up to 77K by decoration. Comparison of FLLs obtained at 55 and 4.2K shows that twisted bond defects are a manifestation of thermal fluctuations at elevated temperature. Analyses of the orientational and translational correlation functions for field and zero-field cooled lattices obtained at 55K suggest that the observed FLL is an equilibrium hexatic. These data were also used to estimate the FLL freezing temperature. {copyright} {ital 1996 The American Physical Society.}
Vortex dynamics and Hall conductivity of hard-core bosons
Lindner, Netanel; Auerbach, Assa; Arovas, Daniel P.
2010-10-01
Magnetotransport of hard-core bosons is studied using an XXZ quantum spin model representation, appropriately gauged on the torus to allow for an external magnetic field. We find strong lattice effects near half filling. An effective quantum mechanical description of the vortex degrees of freedom is derived. Using semiclassical and numerical analysis we compute the vortex-hopping energy t{sub V}, which at half filling is close to magnitude of the boson hopping energy. The critical quantum melting density of the vortex lattice is estimated at 6.5x10{sup -3} vortices per unit cell. The Hall conductance is computed from the Chern numbers of the low-energy eigenstates. At zero temperature, it reverses sign abruptly at half filling. At precisely half filling, all eigenstates are doubly degenerate for any odd number of flux quanta. We prove the exact degeneracies on the torus by constructing an SU(2) algebra of point-group symmetries, associated with the center of vorticity. This result is interpreted as if each vortex carries an internal spin-half degree of freedom, which can manifest itself as a charge density modulation in its core. Our findings suggest interesting experimental implications for vortex motion of cold atoms in optical lattices and magnet transport of short coherence length superconductors.
Scientist Examines Tornado Vortex
NASA Technical Reports Server (NTRS)
1999-01-01
In this Quick Time movie, a scientist examines what appears to be a tornado vortex (blue) coming out of a thunderstorm. The scientist uses 3D glasses to be able to see in 3 dimensions the different flows going out into the vortex. Earth science and weather studies are an important ongoing function of NASA and its affiliates.
Electrostatically Enhanced Vortex Separator
NASA Technical Reports Server (NTRS)
Collins, Earl R.
1993-01-01
Proposed device removes fine particles from high-pressure exhaust gas of chemical reactor. Negatively charged sectors on rotating disks in vortex generator attracts positively charged particles from main stream of exhaust gas. Electrostatic charge enhances particle-separating action of vortex. Gas without particles released to atmosphere.
Improved vortex reactor system
Diebold, James P.; Scahill, John W.
1995-01-01
An improved vortex reactor system for affecting fast pyrolysis of biomass and Refuse Derived Fuel (RDF) feed materials comprising: a vortex reactor having its axis vertically disposed in relation to a jet of a horizontally disposed steam ejector that impels feed materials from a feeder and solids from a recycle loop along with a motive gas into a top part of said reactor.
Houck, Edward D.
1994-01-01
A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.
Vortex distribution in the lowest Landau level
NASA Astrophysics Data System (ADS)
Aftalion, Amandine; Blanc, Xavier; Nier, Francis
2006-01-01
We study the vortex distribution of the wave functions minimizing the Gross-Pitaevskii energy for a fast rotating condensate in the lowest Landau level (LLL): we prove that the minimizer cannot have a finite number of zeroes, thus the lattice is infinite, but not uniform. This uses the explicit expression of the projector onto the LLL. We also show that any slow varying envelope function can be approximated in the LLL by distorting the lattice. This is used in particular to approximate the inverted parabola and understand the role of “invisible” vortices: the distortion of the lattice is very small in the Thomas-Fermi region but quite large outside, where the “invisible” vortices lie.
Vortex cutting in superconductors
NASA Astrophysics Data System (ADS)
Glatz, A.; Vlasko-Vlasov, V. K.; Kwok, W. K.; Crabtree, G. W.
2016-08-01
Vortex cutting and reconnection is an intriguing and still-unsolved problem central to many areas of classical and quantum physics, including hydrodynamics, astrophysics, and superconductivity. Here, we describe a comprehensive investigation of the crossing of magnetic vortices in superconductors using time dependent Ginsburg-Landau modeling. Within a macroscopic volume, we simulate initial magnetization of an anisotropic high temperature superconductor followed by subsequent remagnetization with perpendicular magnetic fields, creating the crossing of the initial and newly generated vortices. The time resolved evolution of vortex lines as they approach each other, contort, locally conjoin, and detach, elucidates the fine details of the vortex-crossing scenario under practical situations with many interacting vortices in the presence of weak pinning. Our simulations also reveal left-handed helical vortex instabilities that accompany the remagnetization process and participate in the vortex crossing events.
Pinning-modulated non-collective Josephson-vortex motion in stacked Josephson junctions.
Jin, Y.-D.; Lee, G.-H.; Lee, H.-J.; Bae, M.-H.; Koshelev, A. E.; Pohang Univ. of Science and Technology; Univ. of Illinois
2009-01-01
Josephson vortices in naturally stacked Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} tunneling junctions display rich dynamic behavior that derives from the coexistence of three basic states: static Josephson vortex lattice, coherently moving lattice, and incoherent quasiparticle tunneling state. The rich structure of hysteretic branches observed in the current-voltage characteristics can be understood as combinatorial combinations of these three states which are realized in different junctions and evolve separately with magnetic field and bias current. In particular, the multiple Josephson vortex flow branches at low-bias currents arise from the individual depinning of Josephson vortex rows in each junction.
NASA Technical Reports Server (NTRS)
Wood, Richard M.; Wilcox, Floyd J., Jr.; Bauer, Steven X. S.; Allen, Jerry M.
2000-01-01
A review of the research conducted at the National Aeronautics and Space Administration (NASA), Langley Research Center (LaRC) into high-speed vortex flows during the 1970s, 1980s, and 1990s is presented. The data reviewed is for flat plates, cavities, bodies, missiles, wings, and aircraft. These data are presented and discussed relative to the design of future vehicles. Also presented is a brief historical review of the extensive body of high-speed vortex flow research from the 1940s to the present in order to provide perspective of the NASA LaRC's high-speed research results. Data are presented which show the types of vortex structures which occur at supersonic speeds and the impact of these flow structures to vehicle performance and control is discussed. The data presented shows the presence of both small- and large scale vortex structures for a variety of vehicles, from missiles to transports. For cavities, the data show very complex multiple vortex structures exist at all combinations of cavity depth to length ratios and Mach number. The data for missiles show the existence of very strong interference effects between body and/or fin vortices and the downstream fins. It was shown that these vortex flow interference effects could be both positive and negative. Data are shown which highlights the effect that leading-edge sweep, leading-edge bluntness, wing thickness, location of maximum thickness, and camber has on the aerodynamics of and flow over delta wings. The observed flow fields for delta wings (i.e. separation bubble, classical vortex, vortex with shock, etc.) are discussed in the context of' aircraft design. And data have been shown that indicate that aerodynamic performance improvements are available by considering vortex flows as a primary design feature. Finally a discussing of a design approach for wings which utilize vortex flows for improved aerodynamic performance at supersonic speed is presented.
Method and apparatus for enhancing vortex pinning by conformal crystal arrays
Janko, Boldizsar; Reichhardt, Cynthia; Reichhardt, Charles; Ray, Dipanjan
2015-07-14
Disclosed is a method and apparatus for strongly enhancing vortex pinning by conformal crystal arrays. The conformal crystal array is constructed by a conformal transformation of a hexagonal lattice, producing a non-uniform structure with a gradient where the local six-fold coordination of the pinning sites is preserved, and with an arching effect. The conformal pinning arrays produce significantly enhanced vortex pinning over a much wider range of field than that found for other vortex pinning geometries with an equivalent number of vortex pinning sites, such as random, square, and triangular.
NASA Technical Reports Server (NTRS)
Lan, C. Edward
1985-01-01
A computer program based on the Quasi-Vortex-Lattice Method of Lan is presented for calculating longitudinal and lateral-directional aerodynamic characteristics of nonplanar wing-body combination. The method is based on the assumption of inviscid subsonic flow. Both attached and vortex-separated flows are treated. For the vortex-separated flow, the calculation is based on the method of suction analogy. The effect of vortex breakdown is accounted for by an empirical method. A summary of the theoretical method, program capabilities, input format, output variables and program job control set-up are described. Three test cases are presented as guides for potential users of the code.
Center vortex model for Sp(2) Yang-Mills theory
Engelhardt, M.; Sperisen, B.
2006-12-15
The question whether the center vortex picture of the strongly interacting vacuum can encompass the infrared dynamics of both SU(2) as well as Sp(2) Yang-Mills theory is addressed. These two theories contain the same center vortex degrees of freedom, and yet exhibit deconfinement phase transitions of different order. This is argued to be caused by the effective action governing the vortices being different in the two cases. To buttress this argument, a random vortex world-surface model is constructed which reproduces available lattice data characterizing Sp(2) Yang-Mills confinement properties. A new effective action term which can be interpreted in terms of a vortex stickiness serves to realize a first-order deconfinement phase transition, as found in Sp(2) Yang-Mills theory. Predictions are given for the behavior of the spatial string tension at finite temperatures.
Vortex Phase Diagram as a Function of Oxygen Deficiency in Untwinned YBa_2Cu_3O_y
NASA Astrophysics Data System (ADS)
Nishizaki, Terukazu
2000-03-01
This talk will present recent results of the vortex phase diagram of untwinned YBa2Cu3Oy (YBCO) single crystals with a different oxygen content under high magnetic fields up to 30T. We show that the first-order vortex lattice melting line T_m(H) and the second-order vortex glass transition line T_g(H) terminate at the critical point H_cp and the field-driven disordering transition line separates the vortex solid phase into the Bragg glass and the vortex glass phases(T. Nishizaki et al., Phys. Rev. B 58, 11169 (1998).). The value of H_cp strongly depends on the oxygen content and the vortex lattice melting transition is observed up to 30 T for fully oxidized YBCO (y~=7, T_c~=87.5 K). For optimally doped YBCO (T_c~= 93 K), on the other hand, T_g(H) decreases with increasing temperature and approaches to the vortex lattice melting line well below the critical point of T_m(H), indicating the existence of the new vortex state such as a vortex slush regime between T_g(H) and T_m(H). Thermodynamic properties are also examined above and below the terminal point of T_g(H). We find that the entropy change at the first-order melting transition becomes considerably small above the terminal field of T_g(H). The novel vortex phase diagram is discussed.
Phase transitions and connectivity in three-dimensional vortex equilibria
Akao, J.H.
1994-05-01
The statistical mechanics of collections of closed self avoiding vortex loops on a lattice are studied. The system is related to the vortex form of the three dimensional XY model and to lattice vortex equilibrium models of turbulence. The system exhibits vortex connectivity and screening effects, and models in vorticity variables the superfluid transition. The equilibrium states of the system are simulated by a grand canonical Monte Carlo method. A set of geometric transformations for self-avoiding loops is developed. The numerical method employs histogram sampling techniques and utilizes a modification to the Metropolis flow which enhances efficiency. Results are given for a region in the temperature-chemical potential plane, where the chemical potential is related to the vortex fugacity. A line of second order transitions is identified at low temperature. The transition is shown to be a percolation threshold at which connected vortex loops of infinite size appear in the system. The nature of the transition supports the assumption that the lambda transition in bulk superfluid helium is driven by vortices. An asymptotic analysis is performed for the energy and entropy scaling of the system as functions of the system size and the lattice spacing. These estimates indicate that the infinite temperature line is a phase boundary between small scale fractal vortices and large scale smooth vortices. A suggestion is made that quantum vortices have uniform structure on the scale of the lattice spacing and lie in the positive temperature regime, while classical vortices have uniform structure on the scale of the domain and lie in the negative temperature regime.
Composite vortex beams by coaxial superposition of Laguerre-Gaussian beams
NASA Astrophysics Data System (ADS)
Huang, Sujuan; Miao, Zhuang; He, Chao; Pang, Fufei; Li, Yingchun; Wang, Tingyun
2016-03-01
We propose the generation of novel composite vortex beams by coaxial superposition of Laguerre-Gaussian (LG) beams with common waist position and waist parameter. Computer-generated holography by conjugate-symmetric extension is applied to produce the holograms of several composite vortex beams. Utilizing the holograms, fantastic light modes including optical ring lattice, double dark-ring and double bright-ring composite vortex beams etc. are numerically reconstructed. The generated composite vortex beams show diffraction broadening with some of them showing dynamic rotation around beam centers while propagating. Optical experiments based on a computer-controlled spatial light modulator (SLM) verify the numerical results. These novel composite vortex beams possess more complicated distribution and more controllable parameters for their potential application in comparison to conventional optical ring lattice.
Motion of a vortex ring in a simple shear flow
NASA Astrophysics Data System (ADS)
Cheng, M.; Lou, J.; Lim, T. T.
2009-08-01
The motion and deformation of a vortex ring in a linear or simple shear flow have been simulated numerically by using the lattice Boltzmann method with multiple relaxation times. The study is motivated by a recent experiment [T. T. Lim, K. B. Lua, and K. Thet, Phys. Fluids 20, 051701 (2008)], which shows that a vortex ring propagating in a uniform cross flow does not experience Kutta lift and undergo tilting and deformation. The focus of the present study is to examine the effect of a simple shear in a cross flow on the motion of a vortex ring. Numerical approach is adopted here because a truly simple shear flow is difficult to generate experimentally. Our computation shows that a vortex ring tilts and deforms in a simple shear flow, and the tilting can be attributed to the modification of the vorticity distribution of the vortex ring as a result of the entrainment of background vorticity by the vortex core. It is further shown that although the shear in the flow has the tendency to elongate the vortex ring, the tilting angle of the ring increases with the shear ratio.
NASA Astrophysics Data System (ADS)
Crowdy, Darren; Marshall, Jonathan
2004-08-01
This paper demonstrates that two well-known equilibrium solutions of the Euler equations—the corotating point vortex pair and the Rankine vortex—are connected by a continuous branch of exact solutions. The central idea is to "grow" new vortex patches at two stagnation points that exist in the frame of reference of the corotating point vortex pair. This is done by generalizing a mathematical technique for constructing vortex equilibria first presented by Crowdy [D. G. Crowdy, "A class of exact multipolar vortices," Phys. Fluids 11, 2556 (1999)]. The solutions exhibit several interesting features, including the merging of two separate vortex patches via the development of touching cusps. Numerical contour dynamics methods are used to verify the mathematical solutions and reveal them to be robust structures. The general issue of how simple vortex equilibria can be continued continuously to more complicated ones with very different vortical topologies is discussed. The solutions are examples of exact solutions of the Euler equations involving multiple interacting vortex patches.
Hairpin Vortex Regeneration Threshold
NASA Astrophysics Data System (ADS)
Sabatino, Daniel; Maharjan, Rijan
2015-11-01
A free surface water channel is used to study hairpin vortex formation created by fluid injection through a narrow slot into a laminar boundary layer. Particle image velocimetry is used to calculate the circulation of the primary hairpin vortex head which is found to monotonically decrease in strength with downstream distance. When a secondary hairpin vortex is formed upstream of the primary vortex, the circulation strength of the head is comparable to the strength of the primary head at the time of regeneration. However, the legs of the primary vortex strengthen up to the moment the secondary hairpin is generated. Although the peak circulation in the legs is not directly correlated to the strength of the original elongated ring vortex, when the circulation is scaled with the injection momentum ratio it is linearly related to scaled injection time. It is proposed that the injection momentum ratio and nondimensionalized injection time based on the wall normal penetration time can be used to identify threshold conditions which produce a secondary vortex. Supported by the National Science Foundation under Grant CBET- 1040236.
NASA Technical Reports Server (NTRS)
Nakamura, Y.; Leonard, A.; Spalart, P. R.
1985-01-01
A vortex breakdown was simulated by the vortex filament method, and detailed figures are presented based on the results. Deformations of the vortex filaments showed clear and large swelling at a particular axial station which implied the presence of a recirculation bubble at that station. The tendency for two breakdowns to occur experimentally was confirmed by the simulation, and the jet flow inside the bubble was well simulated. The particle paths spiralled with expansion, and the streamlines took spiral forms at the breakdown with expansion.
Skyrmion Flux Lattices and their μSR signature
NASA Astrophysics Data System (ADS)
Li, Qi; Toner, John; Belitz, Dietrich
2008-03-01
Recently, topological excitations known as skyrmions were predicted to exist in p-wave superconductors [1]. The elastic theory of an induced skyrmion lattice was developed in [2], and its melting curve was found to be qualitatively different from that for vortex lattices. Here we show that the muon spin resonance (μSR) signatures of the two types of lattices are also very different. μSR has been applied extensively to study the magnetic properties of vortex flux lattices [3]. The observable in this technique is the μSR line shape n(B), which is the probability density that a muon experiences a local magnetic induction B. In a vortex lattice, for small B, n(B) (1/B)/B. By contrast, for a skyrmion lattice we predict n(B) B^ (-3/2). This difference provides another way to easily distinguish between vortex and skyrmion flux lattices, and can thus help to identify p-wave superconductors. [1] A. Knigavko, B. Rosenstein, and Y.F. Chen, Phys. Rev. B 60, 550 (1999). [2] Qi Li, John Toner, and D. Belitz, Phys.Rev. Lett. 98, 187002 (2007). [3] J. E. Sonier, J.H. Brewer, and R. F. Kiefl, Rev. Mod. Phys. 72, 769 (2000).
Universal statistics of vortex lines.
Nahum, Adam; Chalker, J T
2012-03-01
We study the vortex lines that are a feature of many random or disordered three-dimensional systems. These show universal statistical properties on long length scales, and geometrical phase transitions analogous to percolation transitions but in distinct universality classes. The field theories for these problems have not previously been identified, so that while many numerical studies have been performed, a framework for interpreting the results has been lacking. We provide such a framework with mappings to simple supersymmetric models. Our main focus is on vortices in short-range-correlated complex fields, which show a geometrical phase transition that we argue is described by the CP(k|k) model (essentially the CP(n-1) model in the replica limit n→1). This can be seen by mapping a lattice version of the problem to a lattice gauge theory. A related field theory with a noncompact gauge field, the 'NCCP(k|k) model', is a supersymmetric extension of the standard dual theory for the XY transition, and we show that XY duality gives another way to understand the appearance of field theories of this type. The supersymmetric descriptions yield results relevant, for example, to vortices in the XY model and in superfluids, to optical vortices, and to certain models of cosmic strings. A distinct but related field theory, the RP(2l|2l) model (or the RP(n-1) model in the limit n→1) describes the unoriented vortices that occur, for instance, in nematic liquid crystals. Finally, we show that in two dimensions, a lattice gauge theory analogous to that discussed in three dimensions gives a simple way to see the known relation between two-dimensional percolation and the CP(k|k) σ model with a θ term. PMID:22587072
NASA Astrophysics Data System (ADS)
Conlisk, A. T.
1998-11-01
The interaction of vortices with solid surfaces occurs in many different situations including, but not limited to tornadoes, propeller wakes, flows over swept wings and missile forebodies, turbomachinery flows, blade-vortex interactions and tip vortex-surface interactions on helicopters. Often, parts of a system must operate within such flows and thus encounter these vortices. In the present paper we discuss the nature of a particular subset of interactions called ``collisions''. A ``collision'' is characterized by the fact that the core of the vortex is permanently altered; usually the core is locally destroyed. The focus is on fully three-dimensional collisions although two-dimensional collisions are discussed as well. Examples of collisions in helicopter aerodynamics and turbomachinery flows are discussed and the dynamics of the vortex core during a collision process are illustrated for a 90^o collision. ^Supported by the US Army Research Office
NASA Technical Reports Server (NTRS)
Stough, H. P., III; Greene, George C.; Stewart, Eric C.; Stuever, Robert A.; Jordan, Frank L., Jr.; Rivers, Robert A.; Vicroy, Dan D.
1993-01-01
NASA is conducting research that will enable safe improvements in the capacity of the nation's air transportation system. The wake-vortex hazard is a factor in establishing the minimum safe spacing between aircraft during landing and takeoff operations and, thus, impacts airport capacity. The ability to accurately model the wake hazard and determine safe separation distances for a wide range of aircraft and operational scenarios may provide the basis for significant increases in airport capacity. Current and planned NASA research is described which is focused on increasing airport capacity by safely reducing wake-hazard-imposed aircraft separations through advances in a number of technologies including vortex motion and decay prediction, vortex encounter modeling, wake-vortex hazard characterization, and in situ flow sensing.
NASA Technical Reports Server (NTRS)
Cunningham, A. M., Jr.
1986-01-01
An experimental study was conducted to quantify the hysteresis associated with various vortex flow transition points and to determine the effect of planform geometry. The transition points observed consisted of the appearance (or disappearance) of trailing edge vortex burst and the transition to (or from) flat plate or totally separated flows. Flow visualization with smoke injected into the vortices was used to identify the transitions on a series of semi-span models tested in a low speed tunnel. The planforms tested included simple deltas (55 deg to 80 deg sweep), cranked wings with varying tip panel sweep and dihedral, and a straked wing. High speed movies at 1000 frames per second were made of the vortex flow visualization in order to better understand the dynamics of vortex flow, burst and transition.
NASA Technical Reports Server (NTRS)
Rao, D. M.
1983-01-01
Segmented vortex flaps were suggested as a means of delaying the vortex spill-over causing thrust loss over the outboard region of single-panel flaps. Also proposed was hinge-line setback for exploiting leading-edge suction in conjunction with vortex flaps to improve the overall thrust per unit flap area. These two concepts in combination were tested on a 60-deg cropped delta wing model. Significant improvement in flap efficiency was indicated by a reduction of the flap/wing area from 11.4% of single-panel flap to 6.3% of a two segment delta flap design, with no lift/drag penalty at lift coefficients between 0.5 and 0.7. The more efficient vortex flap arrangement of this study should benefit the performance attainable with flaps of given area on wings of moderate leading-edge sweep.
NASA Astrophysics Data System (ADS)
Hrkac, Gino; Keatley, Paul S.; Bryan, Matthew T.; Butler, Keith
2015-11-01
The magnetic vortex has sparked the interest of the academic and industrial communities over the last few decades. From their discovery in the 1970s for bubble memory devices to their modern application as radio frequency oscillators, magnetic vortices have been adopted to modern telecommunication and sensor applications. Basic properties of vortex structures in the static and dynamic regime, from a theoretical and experimental point of view, are presented as well as their application in spin torque driven nano-pillar and magnetic tunnel junction devices. Single vortex excitations and phase locking phenomena of coupled oscillators are discussed with an outlook of vortex oscillators in magnetic hybrid structures with imprinted domain confinement and dynamic encryption devices.
Improved vortex reactor system
Diebold, J.P.; Scahill, J.W.
1995-05-09
An improved vortex reactor system is described for affecting fast pyrolysis of biomass and Refuse Derived Fuel (RDF) feed materials comprising: a vortex reactor having its axis vertically disposed in relation to a jet of a horizontally disposed steam ejector that impels feed materials from a feeder and solids from a recycle loop along with a motive gas into a top part of said reactor. 12 figs.
NASA Technical Reports Server (NTRS)
Betz, A
1933-01-01
Progressive application of the Kutta-Joukowsky theorem to the relationship between airfoil lift and circulation affords a number of formulas concerning the conduct of vortex systems. The application of this line of reasoning to several problems of airfoil theory yields an insight into many hitherto little observed relations. This report is confined to plane flow, hence all vortex filaments are straight and mutually parallel (perpendicular to the plane of flow).
Houck, E.D.
1994-05-17
A fluid transfer system is described that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other. 10 figures.
Buoyant Norbury's vortex rings
NASA Astrophysics Data System (ADS)
Blyth, Mark; Rodriguez-Rodriguez, Javier; Salman, Hayder
2014-11-01
Norbury's vortices are a one-parameter family of axisymmetric vortex rings that are exact solutions to the Euler equations. Due to their relative simplicity, they are extensively used to model the behavior of real vortex rings found in experiments and in Nature. In this work, we extend the original formulation of the problem to include buoyancy effects for the case where the fluid that lies within the vortex has a different density to that of the ambient. In this modified formulation, buoyancy effects enter the problem through the baroclinic term of the vorticity equation. This permits an efficient numerical solution of the governing equation of motion in terms of a vortex contour method that tracks the evolution of the boundary of the vortex. Finally, we compare our numerical results with the theoretical analysis of the short-time evolution of a buoyant vortex. Funded by the Spanish Ministry of Economy and Competitiveness through grant DPI2011-28356-C03-02 and by the London Mathematical Society.
Glory, Vortex Street off Baja California
NASA Technical Reports Server (NTRS)
2007-01-01
On June 19, 2007, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured both a vortex street and a glory visible amid the lattice of clouds over the Pacific Ocean off Baja California. In this image, the swirling clouds known as vortex streets appear along the left edge of the image, stretching southward from Isla Guadalupe. Another NASA satellite captured an earlier example of vortex streets in June 2000. These atmospheric vortices, known as Von Karman vortex streets, often occur in the wake of an obstacle to air flow, such as an island. Stratocumulus clouds--low-lying, sheets of puffy clouds-- over the ocean show the impact of the island on air flow visible though their alternating pattern of clockwise and counter-clockwise swirls. Southeast of the vortex street, a glory, which resembles a rainbow, hovers above the cloud cover. The glory is faint but large, 200 to 300 kilometers long, along a north-south orientation. This phenomenon can occur when the satellite passes directly between the Sun and a bank of clouds below. (People also observe them while looking down on clouds from airplanes.) Not just any kind of cloud can produce a glory; only clouds composed entirely of water droplets (as opposed to ice crystals) can make them. The droplets that form glories generally have diameters of less than 50 micrometers (a micrometers is a millionth of a meter). The water droplets bend the light, showing its different wavelengths, or colors. In this glory, reds and oranges are most visible. NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center.
Yaron, U.; Gammel, P.; Boebinger, G.; Aeppli, G.; Schiffer, P.; Bucher, E.; Bishop, D.; Broholm, C.; Mortensen, K.
1997-04-01
Small angle neutron scattering studies of the flux line lattice (FLL) in UPt{sub 3} for fields {bold H}{perpendicular}{bold c} provide direct microscopic evidence for the 5kOe B{r_arrow}C transition. We find a pronounced maximum in the longitudinal correlation length of the FLL at the transition and an abrupt change in the field dependence of the scattered intensity which can be interpreted as a 15{percent} decrease in the coherence length and a 9{percent} increase in the penetration depth, consistent with discontinuities in the critical fields. Finally, in the low field phase, the FLL distortion evolves roughly linearly with field, while in the high field phase it appears to be less field dependent. {copyright} {ital 1997} {ital The American Physical Society}
Symmetric Z2 spin liquids and their neighboring phases on triangular lattice
NASA Astrophysics Data System (ADS)
Lu, Yuan-Ming
2016-04-01
Motivated by recent numerical discovery of a gapped spin liquid phase in spin-1 /2 triangular-lattice J1-J2 Heisenberg model, we classify symmetric Z2 spin liquids on triangular lattice in the Abrikosov-fermion representation. We find 20 phases with distinct spinon symmetry quantum numbers, eight of which have their counterparts in the Schwinger-boson representation. Among them we identify two promising candidates (#1 and #20), which can realize a gapped Z2 spin liquid with up to next nearest neighbor mean-field amplitudes. We analyze their neighboring magnetic orders and valence bond solid patterns, and find one state (#20) that is connected to 120-degree Neel order by a continuous quantum phase transition. We also identify gapped nematic Z2 spin liquids in the neighborhood of the symmetric states and find three promising candidates (#1, #6, and #20).
Bornyakov, V.G.
2005-06-01
Possibilities that are provided by a lattice regularization of QCD for studying nonperturbative properties of QCD are discussed. A review of some recent results obtained from computer calculations in lattice QCD is given. In particular, the results for the QCD vacuum structure, the hadron mass spectrum, and the strong coupling constant are considered.
Defect pair in the elastic lattice of pancake vortices
Slutzky, M.; Mints, R.G.; Brandt, E.H.
1997-07-01
An additional pancake-antipancake vortex pair is considered in the vortex lattice of layered superconductors. Within linear elastic continuum theory, the relaxation of the background lattice screens the long-range logarithmic interaction of the defect pair, reducing the factor ln(r{sub 0}/{xi}) to ln(a/{xi}) where r{sub 0} is the pair spacing, {xi} the in-plane coherence length, and a the vortex spacing. The finite tilt modulus does not destroy this ideal two-dimensional screening, yielding a small correction {approximately}(a{sup 2}/8{pi}{lambda}{sup 2})ln(r{sub 0}/a), which in principle is of long range, but has a very small prefactor when the vortex spacing a is smaller than the in-plane penetration depth {lambda}. {copyright} {ital 1997} {ital The American Physical Society}
Vortex states in superconductors with strong Pauli-paramagnetic effect
NASA Astrophysics Data System (ADS)
Ichioka, Masanori; Machida, Kazushige
2007-08-01
Using quasiclassical theory, we analyze the vortex structure of strong-paramagnetic superconductors. There, induced paramagnetic moments are accumulated exclusively around the vortex core. We quantitatively evaluate the significant paramagnetic effect in the H dependence of various quantities, such as low temperature specific heat, Knight shift, magnetization, and the flux line lattice (FLL) form factor. The anomalous H dependence of the FLL form factor observed by the small angle neutron scattering in CeCoIn5 is attributable to the large paramagnetic contribution.
Vortex Solutions of the Defocusing Discrete Nonlinear Schroedinger Equation
Cuevas, J.; Kevrekidis, P. G.; Law, K. J. H.
2009-09-09
We consider the existence, stability and dynamical evolution of dark vortex states in the two-dimensional defocusing DNLS equation, a model of interest both to atomic physics and to nonlinear optics. Our considerations are chiefly based on initializing such vortex configurations at the anti-continuum limit of zero coupling between adjacent sites, and continuing them to finite values of the coupling. Discrete defocusing vortices become unstable past a critical coupling strength and, subsequently feature a cascade of alternating stabilization-destabilization windows for any finite lattice.
Magnetic Vortex Induced by Nonmagnetic Impurity in Frustrated Magnets
NASA Astrophysics Data System (ADS)
Lin, Shi-Zeng; Hayami, Satoru; Batista, Cristian D.
2016-05-01
We study the effect of a nonmagnetic impurity inserted in a two-dimensional frustrated ferromagnet above its saturation magnetic field Hsat for arbitrary spin S . We demonstrate that the ground state includes a magnetic vortex that is nucleated around the impurity over a finite range of magnetic field Hsat≤H ≤HsatI. Upon approaching the quantum critical point at H =Hsat, the radius of the magnetic vortex diverges as the magnetic correlation length: ξ ∝1 /√{H -Hsat }. These results are derived both for the lattice and in the continuum limit.
Magnetic Vortex Induced by Nonmagnetic Impurity in Frustrated Magnets.
Lin, Shi-Zeng; Hayami, Satoru; Batista, Cristian D
2016-05-01
We study the effect of a nonmagnetic impurity inserted in a two-dimensional frustrated ferromagnet above its saturation magnetic field H_{sat} for arbitrary spin S. We demonstrate that the ground state includes a magnetic vortex that is nucleated around the impurity over a finite range of magnetic field H_{sat}≤H≤H_{sat}^{I}. Upon approaching the quantum critical point at H=H_{sat}, the radius of the magnetic vortex diverges as the magnetic correlation length: ξ∝1/sqrt[H-H_{sat}]. These results are derived both for the lattice and in the continuum limit. PMID:27203342
Dual vortex theory of doped Mott insulators
Balents, Leon; Sachdev, Subir
2007-11-15
We present a general framework for describing the quantum phases obtained by doping paramagnetic Mott insulators on the square lattice. The undoped insulators are efficiently characterized by the projective transformations of various fields under the square lattice space group (the PSG). We show that the PSG also imposes powerful constraints on the doped system, and on the effective action for the vortex and Bogoliubov quasiparticle excitations of superconducting states. This action can also be extended across transitions to supersolid or insulating states at non-zero doping. For the case of a valence bond solid (VBS) insulator, we show that the doped system has the same PSG as that of elementary bosons with density equal to the density of electron Cooper pairs. We also discuss aspects of the action for a d-wave superconductor obtained by doping a 'staggered-flux' spin liquid state.
Point-vortex approach in two-dimensional turbulence
NASA Astrophysics Data System (ADS)
Kuvshinov, B. N.; Schep, T. J.
2016-05-01
The properties of two-dimensional turbulence in a circular domain are investigated within the framework of the punctuated point-vortex model. Vortex dynamics is governed by Hamiltonian equations, and it is interrupted by instantaneous events resulting in vortex merging. Motion of about 100 point vortices is simulated using an accurate, symplectic integration method. Ensembles of like-sign vortices relax to a quasi-lattice state. Vortices with zero total vorticity tend to be randomized. Their motion still does not become fully chaotic. We observe emergence of long lived large dipoles (co-propagating pairs of vortices with opposite signs), which affect the evolution of the whole vortex ensemble. The presence of such dipoles accelerate the vortex decay rate. The decay exponent has been estimated as ξ ≃ 1.7, which is much larger than ξ ≃ 0.7, reported in previous studies of decaying turbulence. Since dipole dynamics depends on specific properties of the point vortex system, our findings suggest that a universal decay exponent in such systems does not exist.
A relativistic spherical vortex
Pekeris, C. L.
1976-01-01
This investigation is concerned with stationary relativistic flows of an inviscid and incompressible fluid. In choosing a density-pressure relation to represent relativistic “incompressibility,” it is found that a fluid in which the velocity of sound equals the velocity of light is to be preferred for reasons of mathematical simplicity. In the case of axially symmetric flows, the velocity field can be derived from a stream function obeying a partial differential equation which is nonlinear. A transformation of variables is found which makes the relativistic differential equation linear. An exact solution is obtained for the case of a vortex confined to a stationary sphere. One can make all three of the components of velocity vanish on the surface of the sphere, as in the nonrelativistic Hicks spherical vortex. In the case of an isolated vortex on whose surface the pressure is made to vanish, it is found that the pressure at the center of the sphere becomes negative, as in the nonrelativistic case. A solution is also obtained for a relativistic vortex advancing in a fluid. The sphere is distorted into an oblate spheroid. The maximum possible velocity of advance of the vortex is (2/3) c. PMID:16578745
Vortex Apparatus and Demonstrations
NASA Astrophysics Data System (ADS)
Shakerin, Said
2010-05-01
Vortex flow, from millimeter to kilometer in scale, is important in many scientific and technological areas. Examples are seen in water strider locomotion, from industrial pipe flow (wastewater treatment) to air traffic control (safe distance between aircrafts on a runway ready for takeoff) to atmospheric studies.2-5 In this paper, we focus on a particular vortex known as bathtub vortex (BTV). It occurs when water is drained from a hole at the bottom of a container such as a bathtub or a sink under the action of gravity. The vortex has a funnel shape with a central air core, resembling a tornado. We have designed a portable apparatus to demonstrate bathtub vortex on a continual basis. The apparatus consists of a clear cylinder supported by a frame over a water reservoir and a submersible pump. Young and old have been equally amazed by watching the demonstrations at various public presentations held at the University of the Pacific recently. With material cost of less than 100, the apparatus can be easily fabricated and used at other universities. With a short set-up time, it is an ideal device for promoting science to the general public, and it can be used to enhance lectures in physics courses as well.
A one-dimensional chain state of vortex matter.
Grigorenko, A; Bending, S; Tamegai, T; Ooi, S; Henini, M
2001-12-13
Magnetic flux penetrates isotropic type II superconductors in flux-quantized vortices, which arrange themselves into a lattice structure that is independent of the direction of the applied field. In extremely anisotropic high-transition-temperature (high-Tc) superconductors, a lattice of stacks of circular 'pancake' vortices forms when a magnetic field is applied perpendicular to the copper oxide layers, while an orthogonal elongated lattice of elliptical Josephson vortices forms when the applied field is parallel to the layers. Here we report that when a tilted magnetic field is applied to single crystals of Bi2Sr2CaCu2O8+delta, these lattices can interact to form a new state of vortex matter in which all stacks of pancake vortices intersect the Josephson vortices. The sublattice of Josephson vortices can therefore be used to manipulate the sublattice of pancake vortices. This result explains the suppression of irreversible magnetization by in-plane fields as seen in Bi2Sr2CaCu2O8+delta crystals, a hitherto mysterious observation. The ability to manipulate sublattices could be important for flux-logic devices, where a 'bit' might be represented by a pancake vortex stack, and the problem of vortex positioning is overcome through sublattice interactions. This also enables the development of flux transducers and amplifiers, considerably broadening the scope for applications of anisotropic high-Tc superconductors. PMID:11742393
Vortex soliton motion and steering
NASA Astrophysics Data System (ADS)
Christou, Jason; Tikhonenko, Vladimir; Kivshar, Yuri S.; Luther-Davies, Barry
1996-10-01
Experimental demonstration of the steering of an optical vortex soliton by the superposition of a weak coherent background field is presented. A model to account for vortex motion is derived, and its validity is verified experimentally and numerically.
Aircraft vortex marking program
NASA Technical Reports Server (NTRS)
Pompa, M. F.
1979-01-01
A simple, reliable device for identifying atmospheric vortices, principally as generated by in-flight aircraft and with emphasis on the use of nonpolluting aerosols for marking by injection into such vortex (-ices) is presented. The refractive index and droplet size were determined from an analysis of aerosol optical and transport properties as the most significant parameters in effecting vortex optimum light scattering (for visual sighting) and visual persistency of at least 300 sec. The analysis also showed that a steam-ejected tetraethylene glycol aerosol with droplet size near 1 micron and refractive index of approximately 1.45 could be a promising candidate for vortex marking. A marking aerosol was successfully generated with the steam-tetraethylene glycol mixture from breadboard system hardware. A compact 25 lb/f thrust (nominal) H2O2 rocket chamber was the key component of the system which produced the required steam by catalytic decomposition of the supplied H2O2.
Reconnection of superfluid vortex bundles.
Alamri, Sultan Z; Youd, Anthony J; Barenghi, Carlo F
2008-11-21
Using the vortex filament model and the Gross-Pitaevskii nonlinear Schroedinger equation, we show that bundles of quantized vortex lines in He II are structurally robust and can reconnect with each other maintaining their identity. We discuss vortex stretching in superfluid turbulence and show that, during the bundle reconnection process, kelvin waves of large amplitude are generated, in agreement with the finding that helicity is produced by nearly singular vortex interactions in classical Euler flows. PMID:19113421
Vortex Characterization for Engineering Applications
Jankun-Kelly, M; Thompson, D S; Jiang, M; Shannahan, B; Machiraju, R
2008-01-30
Realistic engineering simulation data often have features that are not optimally resolved due to practical limitations on mesh resolution. To be useful to application engineers, vortex characterization techniques must be sufficiently robust to handle realistic data with complex vortex topologies. In this paper, we present enhancements to the vortex topology identification component of an existing vortex characterization algorithm. The modified techniques are demonstrated by application to three realistic data sets that illustrate the strengths and weaknesses of our approach.
ERIC Educational Resources Information Center
Parris, Richard
2011-01-01
Given a segment that joins two lattice points in R[superscript 3], when is it possible to form a lattice cube that uses this segment as one of its twelve edges? A necessary and sufficient condition is that the length of the segment be an integer. This paper presents an algorithm for finding such a cube when the prime factors of the length are…
Evolution of an elliptic vortex ring in a viscous fluid
NASA Astrophysics Data System (ADS)
Cheng, M.; Lou, J.; Lim, T. T.
2016-03-01
The evolution of a viscous elliptic vortex ring in an initially quiescent fluid or a linear shear flow is numerically simulated using a lattice Boltzmann method. A wide range of parameters are considered, namely, aspect ratios (AR) (1 ≤ AR ≤ 8), core radius to ring radius ratios (σ0) (0.1 ≤ σ0 ≤ 0.3), Reynolds number (Re) (500 ≤ Re ≤ 3000), and shear rate (K) (0 ≤ K ≤ 0.12). The study aims to fill the gap in the current knowledge of the dynamics of an elliptic vortex ring in a viscous fluid and also to address the issue of whether an elliptic ring undergoes vortex stretching and compression during axis-switching. In a quiescent fluid, results show that for fixed Re and σ0, there exists a critical aspect ratio (ARc), below which an elliptic ring undergoes oscillatory deformation with the period that increases with increasing AR. Above ARc, the vortex ring breaks up into two or three sub-rings after the first half-cycle of oscillation. While higher Reynolds number enhances vortex ring breakup, larger core size has the opposite effect. Contrary to an inviscid theory, an elliptic ring does undergo vortex stretching and compression during oscillatory deformation. In the presence of a linear shear flow, the vortex ring undergoes not only oscillatory deformation and stretching but also tilting as it propagates downstream. The tilting angle increases with the shear rate K and is responsible for inducing a "tail" that consists of a counter-rotating vortex pair (CVP) near the upstream end of the initial major axis after the first half-cycle of oscillation. For a high shear rate, the CVP wraps around the ring and transforms its topological structure from a simple elliptic geometry to a complicated structure that eventually leads to the generation of turbulence.
NASA Technical Reports Server (NTRS)
1977-01-01
A status report is presented on research directed at reducing the vortex disturbances of aircraft wakes. The objective of such a reduction is to minimize the hazard to smaller aircraft that might encounter these wakes. Inviscid modeling was used to study trailing vortices and viscous effects were investigated. Laser velocimeters were utilized in the measurement of aircraft wakes. Flight and wind tunnel tests were performed on scale and full model scale aircraft of various design. Parameters investigated included the effect of wing span, wing flaps, spoilers, splines and engine thrust on vortex attenuation. Results indicate that vortives may be alleviated through aerodynamic means.
Koiller, Jair
2009-05-06
A pair of infinitesimally close opposite vortices moving on a curved surface moves along a geodesic, according to a conjecture by Kimura. We outline a proof. Numerical simulations are presented for a pair of opposite vortices at a close but nonzero distance on a surface of revolution, the catenoid. We conjecture that the vortex pair system on a triaxial ellipsoid is a KAM perturbation of Jacobi's geodesic problem. We outline some preliminary calculations required for this study. Finding the surfaces for which the vortex pair system is integrable is in order.
Nanostructure of vortex during explosion welding.
Rybin, V V; Greenberg, B A; Ivanov, M A; Patselov, A M; Antonova, O V; Elkina, O A; Inozemtsev, A V; Salishchev, G A
2011-10-01
The microstructure of a bimetallic joint made by explosion welding of orthorhombic titanium aluminide (Ti-30Al-16Nb-1Zr-1Mo) with commercially pure titanium is studied. It is found that the welded joint has a multilayered structure including a severely deformed zone observed in both materials, a recrystallized zone of titanium, and a transition zone near the interface. Typical elements of the transition zone-a wavy interface, macrorotations of the lattice, vortices and tracks of fragments of the initial materials-are determined. It is shown that the observed vortices are formed most probably due to local melting of the material near the contact surface. Evidence for this assumption is deduced from the presence of dipoles, which consist of two vortices of different helicity and an ultrafine duplex structure of the vortex. Also, high mixing of the material near the vortex is only possible by the turbulent transport whose coefficient is several orders of magnitude larger than the coefficient of atomic diffusion in liquids. The role played by fragmentation in both the formation of lattice macrorotations and the passage of coarse particles of one material through the bulk of the other is determined. PMID:22400276
NASA Technical Reports Server (NTRS)
Maskew, B.
1975-01-01
The close-approach problem associated with flow calculation methods based on vortex-lattice theory was examined numerically using two-dimensional discretized vortex sheets. The analysis first yields a near-field radius of approximately the distance apart of the vortices in the lattice; only within this distance from the sheet are the errors arising from the discretization significant. Various modifications to the discrete vortices are then considered with the objective of reducing the errors. This leads to a near-field model in which a vortex splits into an increasing number of subvortices as it is approached. The subvortices, whose strengths vary linearly from the vortex position, are evenly distributed along an interpolated curve passing through the basic vortices. This subvortex technique can be extended to the three-dimensional case and is efficient because the number of vortices is effectively increased, but only where and when needed.
Theoretical study of aerodynamic characteristics of wings having vortex flow
NASA Technical Reports Server (NTRS)
Reddy, C. S.
1979-01-01
The aerodynamic characteristics of slender wings having separation induced vortex flows are investigated by employing three different computer codes--free vortex sheet, quasi vortex lattice, and suction analogy methods. Their capabilities and limitations are examined, and modifications are discussed. Flat wings of different configurations: arrow, delta, and diamond shapes, as well as cambered delta wings, are studied. The effect of notch ratio on the load distributions and the longitudinal characteristics of a family of arrow and diamond wings is explored. The sectional lift coefficients and the accumulated span loadings are determined for an arrow wing and are seen to be unusual in comparison with the attached flow results. The theoretically predicted results are compared with the existing experimental values.