Rotating Bose-Einstein condensates with attractive interactions
Kavoulakis, G.M.; Jackson, A.D.; Baym, Gordon
2004-10-01
We examine the phase diagram of a Bose-Einstein condensate of atoms, interacting with an attractive pseudopotential, in a quadratic-plus-quartic potential trap rotating at a given rate. Investigating the behavior of the gas as a function of interaction strength and rotational frequency of the trap, we find that the phase diagram has three distinct phases: one with vortex excitation, one with center-of-mass excitation, and an unstable phase in which the gas collapses.
NASA Astrophysics Data System (ADS)
Palpacelli, Silvia; Succi, Sauro
Following an idea first proposed by Penrose in 1996 to explain the problem of quantum state reduction as a gravitational effect, Moroz, Penrose and Tod1 have shown that quantum state reduction due to gravitational interactions could take place in about one second for the case of 1011 nucleons. However, keeping 1011 nucleons together in a quantum macroscopic state does not appear to be feasible as yet. The closest physical system to such a situation is provided by Bose-Einstein condensates (BEC) with attractive interactions. We present numerical simulations of the Schrödinger-Newton equations, which show that an attractive BEC with 103 atoms would yield a decorrelation time of the order of 10-2 seconds. Hence, a "Penrose-like" reduction, induced by BEC attractive interaction instead of gravity, might be observable and possibly monitored in current BEC experiments with attractive interactions.
Maucher, F.; Skupin, S.; Shen, M.; Krolikowski, W.
2010-06-15
We study formation of rotating three-dimensional high-order solitons (azimuthons) in Bose Einstein condensate with attractive nonlocal nonlinear interaction. In particular, we demonstrate formation of toroidal rotating solitons and investigate their stability. We show that variational methods allow a very good approximation of such solutions and predict accurately the soliton rotation frequency. We also find that these rotating localized structures are very robust and persist even if the initial condensate conditions are rather far from the exact soliton solutions. Furthermore, the presence of repulsive contact interaction does not prevent the existence of those solutions, but allows one to control their rotation. We conjecture that self-trapped azimuthons are generic for condensates with attractive nonlocal interaction.
Criterion for Bose-Einstein condensation in a harmonic trap in the case with attractive interactions
Gajda, Mariusz
2006-02-15
Using a model many-body wave function I analyze the standard criterion for Bose-Einstein condensation and its relation to coherence properties of the system. I pay special attention to an attractive condensate under such a condition that a characteristic length scale of the spatial extension of its center of mass differs significantly from length scales of relative coordinates. I show that although no interference fringes are produced in the two-slit Young interference experiment performed on this system, fringes of a high visibility can be observed in a conditional simultaneous detection of two particles.
Kartsev, P.F.
2003-12-01
We present the results of an exact numeric simulation of N one-dimensional bosons with attractive {delta}-functional interaction in a rotating ring. We prove that even at intermediate values of N, the system can be described by conventional methods of weakly interacting gas, the dimensionless parameter of weak interaction being just 1/N. When the strength of interaction is less than a certain threshold value, the dependence of angular momentum on the rotation frequency features plateaus characteristic of the irrotational fluid.
{sup 39}K Bose-Einstein Condensate with Tunable Interactions
Roati, G.; Zaccanti, M.; D'Errico, C.; Catani, J.; Inguscio, M.; Modugno, G.; Modugno, M.; Simoni, A.
2007-07-06
We produce a Bose-Einstein condensate of {sup 39}K atoms. Condensation of this species with a naturally small and negative scattering length is achieved by a combination of sympathetic cooling with {sup 87}Rb and direct evaporation, exploiting the magnetic tuning of both inter- and intraspecies interactions at Feshbach resonances. We explore the tunability of the self-interactions by studying the expansion and the stability of the condensate. We find that a {sup 39}K condensate is interesting for future experiments requiring a weakly-interacting Bose gas.
Double Species Bose-Einstein Condensate with Tunable Interspecies Interactions
Thalhammer, G.; Barontini, G.; De Sarlo, L.; Catani, J.; Minardi, F.; Inguscio, M.
2008-05-30
We produce Bose-Einstein condensates of two different species, {sup 87}Rb and {sup 41}K, in an optical dipole trap in proximity of interspecies Feshbach resonances. We discover and characterize two Feshbach resonances, located around 35 and 79 G, by observing the three-body losses and the elastic cross section. The narrower resonance is exploited to create a double species condensate with tunable interactions. Our system opens the way to the exploration of double species Mott insulators and, more in general, of the quantum phase diagram of the two-species Bose-Hubbard model.
Atom Interferometry with a Weakly Interacting Bose-Einstein Condensate
Fattori, M.; D'Errico, C.; Roati, G.; Inguscio, M.; Modugno, G.; Zaccanti, M.; Jona-Lasinio, M.; Modugno, M.
2008-02-29
We demonstrate the operation of an atom interferometer based on a weakly interacting Bose-Einstein condensate. We strongly reduce the interaction induced decoherence that usually limits interferometers based on trapped condensates by tuning the s-wave scattering length almost to zero via a magnetic Feshbach resonance. We employ a {sup 39}K condensate trapped in an optical lattice, where Bloch oscillations are forced by gravity. The fine-tuning of the scattering length down to 0.1 a{sub 0} and the micrometric sizes of the atomic sample make our system a very promising candidate for measuring forces with high spatial resolution. Our technique can be in principle extended to other measurement schemes opening new possibilities in the field of trapped atom interferometry.
85Rb tunable-interaction Bose-Einstein condensate machine.
Altin, P A; Robins, N P; Döring, D; Debs, J E; Poldy, R; Figl, C; Close, J D
2010-06-01
We describe our experimental setup for creating stable Bose-Einstein condensates (BECs) of (85)Rb with tunable interparticle interactions. We use sympathetic cooling with (87)Rb in two stages, initially in a tight Ioffe-Pritchard magnetic trap and subsequently in a weak, large-volume, crossed optical dipole trap, using the 155 G Feshbach resonance to manipulate the elastic and inelastic scattering properties of the (85)Rb atoms. Typical (85)Rb condensates contain 4 x 10(4) atoms with a scattering length of a=+200a(0). Many aspects of the design presented here could be adapted to other dual-species BEC machines, including those involving degenerate Fermi-Bose mixtures. Our minimalist apparatus is well suited to experiments on dual-species and spinor Rb condensates, and has several simplifications over the (85)Rb BEC machine at JILA, which we discuss at the end of this article. PMID:20590221
Observation of Attractive and Repulsive Polarons in a Bose-Einstein Condensate.
Jørgensen, Nils B; Wacker, Lars; Skalmstang, Kristoffer T; Parish, Meera M; Levinsen, Jesper; Christensen, Rasmus S; Bruun, Georg M; Arlt, Jan J
2016-07-29
The problem of an impurity particle moving through a bosonic medium plays a fundamental role in physics. However, the canonical scenario of a mobile impurity immersed in a Bose-Einstein condensate (BEC) has not yet been realized. Here, we use radio frequency spectroscopy of ultracold bosonic ^{39}K atoms to experimentally demonstrate the existence of a well-defined quasiparticle state of an impurity interacting with a BEC. We measure the energy of the impurity both for attractive and repulsive interactions, and find excellent agreement with theories that incorporate three-body correlations, both in the weak-coupling limits and across unitarity. The spectral response consists of a well-defined quasiparticle peak at weak coupling, while for increasing interaction strength, the spectrum is strongly broadened and becomes dominated by the many-body continuum of excited states. Crucially, no significant effects of three-body decay are observed. Our results open up exciting prospects for studying mobile impurities in a bosonic environment and strongly interacting Bose systems in general. PMID:27517777
Observation of Attractive and Repulsive Polarons in a Bose-Einstein Condensate.
Jørgensen, Nils B; Wacker, Lars; Skalmstang, Kristoffer T; Parish, Meera M; Levinsen, Jesper; Christensen, Rasmus S; Bruun, Georg M; Arlt, Jan J
2016-07-29
The problem of an impurity particle moving through a bosonic medium plays a fundamental role in physics. However, the canonical scenario of a mobile impurity immersed in a Bose-Einstein condensate (BEC) has not yet been realized. Here, we use radio frequency spectroscopy of ultracold bosonic ^{39}K atoms to experimentally demonstrate the existence of a well-defined quasiparticle state of an impurity interacting with a BEC. We measure the energy of the impurity both for attractive and repulsive interactions, and find excellent agreement with theories that incorporate three-body correlations, both in the weak-coupling limits and across unitarity. The spectral response consists of a well-defined quasiparticle peak at weak coupling, while for increasing interaction strength, the spectrum is strongly broadened and becomes dominated by the many-body continuum of excited states. Crucially, no significant effects of three-body decay are observed. Our results open up exciting prospects for studying mobile impurities in a bosonic environment and strongly interacting Bose systems in general.
Observation of Attractive and Repulsive Polarons in a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Jørgensen, Nils B.; Wacker, Lars; Skalmstang, Kristoffer T.; Parish, Meera M.; Levinsen, Jesper; Christensen, Rasmus S.; Bruun, Georg M.; Arlt, Jan J.
2016-07-01
The problem of an impurity particle moving through a bosonic medium plays a fundamental role in physics. However, the canonical scenario of a mobile impurity immersed in a Bose-Einstein condensate (BEC) has not yet been realized. Here, we use radio frequency spectroscopy of ultracold bosonic 39K atoms to experimentally demonstrate the existence of a well-defined quasiparticle state of an impurity interacting with a BEC. We measure the energy of the impurity both for attractive and repulsive interactions, and find excellent agreement with theories that incorporate three-body correlations, both in the weak-coupling limits and across unitarity. The spectral response consists of a well-defined quasiparticle peak at weak coupling, while for increasing interaction strength, the spectrum is strongly broadened and becomes dominated by the many-body continuum of excited states. Crucially, no significant effects of three-body decay are observed. Our results open up exciting prospects for studying mobile impurities in a bosonic environment and strongly interacting Bose systems in general.
Matter-wave interactions in two-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Li, Sheng-Chang; Dou, Fu-Quan
2015-08-01
We investigate two vector-soliton-like matter waves collisions in two-component Bose-Einstein condensates with attractive interactions and Gaussian barrier. We present a detailed numerical analysis of the roles of atomic interactions, barrier, relative velocity, and relative phase in collisional dynamics. We show that the interspecies interactions are crucial to make the wave packet propagate as a “breather”. We find that the collision-induced trajectory shifts of waves are mainly determined by the intraspecies interactions and proportional to them in the weak nonlinearity regime. Moreover, we explore the meeting time of colliding waves and find it depends on the competition between barrier potential and atomic interactions. Particularly, we study the collisions of two waves with a slight velocity asymmetry (or with different relative phases) and the waves merging and split are demonstrated. The underlying inelastic mechanism closely related to energy exchange is briefly discussed as well.
Swift Loss of Coherence of Soliton Trains in Attractive Bose-Einstein Condensates
Streltsov, Alexej I.; Cederbaum, Lorenz S.; Alon, Ofir E.
2011-06-17
Experiments on ultracold attractive Bose-Einstein condensates (BECs) have demonstrated that at low dimensions atomic clouds can form localized objects, propagating for long times without significant changes in their shapes and attributed to bright matter-wave solitons, which are coherent objects. We consider the dynamics of bright soliton trains from the perspective of many-boson physics. The fate of matter-wave soliton trains is actually to quickly lose their coherence and become macroscopically fragmented BECs. The death of the coherent matter-wave soliton trains gives birth to fragmented objects, whose quantum properties and experimental signatures differ substantially from what is currently assumed.
Swift loss of coherence of soliton trains in attractive Bose-Einstein condensates.
Streltsov, Alexej I; Alon, Ofir E; Cederbaum, Lorenz S
2011-06-17
Experiments on ultracold attractive Bose-Einstein condensates (BECs) have demonstrated that at low dimensions atomic clouds can form localized objects, propagating for long times without significant changes in their shapes and attributed to bright matter-wave solitons, which are coherent objects. We consider the dynamics of bright soliton trains from the perspective of many-boson physics. The fate of matter-wave soliton trains is actually to quickly lose their coherence and become macroscopically fragmented BECs. The death of the coherent matter-wave soliton trains gives birth to fragmented objects, whose quantum properties and experimental signatures differ substantially from what is currently assumed.
Nonlinear Dynamics of Bose-Einstein Condensates with Long-Range Interactions
Wunner, G.; Cartarius, H.; Fabcic, T.; Koeberle, P.; Main, J.; Schwidder, T.
2008-11-13
The motto of this paper is: Let's face Bose-Einstein condensation through nonlinear dynamics. We do this by choosing variational forms of the condensate wave functions (of given symmetry classes), which convert the Bose-Einstein condensates via the time-dependent Gross-Pitaevskii equation into Hamiltonian systems that can be studied using the methods of nonlinear dynamics. We consider in particular cold quantum gases where long-range interactions between the neutral atoms are present, in addition to the conventional short-range contact interaction, viz. gravity-like interactions, and dipole-dipole interactions. The results obtained serve as a useful guide in the search for nonlinear dynamics effects in numerically exact quantum calculations for Bose-Einstein condensates. A main result is the prediction of the existence of stable islands as well as chaotic regions for excited states of dipolar condensates, which could be checked experimentally.
Properties of Two-Component Bose-Einstein Condensates with Monopolar Interaction
NASA Astrophysics Data System (ADS)
Li, Jinbin; Qiao, Yaxin
2014-11-01
We study two-component Bose-Einstein condensates (BECs) with electromagnetically induced attractive monopolar interaction, by means of the Dirac-Frenkel-McLachlan variational principle. The effectiveness of external trap potential, inter-component -wave scattering, monopolar interaction, and particle numbers on the density of BECs is investigated. It is shown that the trap potential dramatically affects density profiles compared to the other three ingredients. Atoms with smaller intra-component -wave scattering length will be squeezed out when monopolar interaction or particle numbers are small, whereas the atoms in the other component are pushed out instead when either parameter is large enough. This is in contrast to modulation of inter-component -wave scattering length, which can not exchange the relative location of different components.
Bragg Spectroscopy of a Strongly Interacting {sup 85}Rb Bose-Einstein Condensate
Papp, S. B.; Pino, J. M.; Wild, R. J.; Ronen, S.; Jin, D. S.; Cornell, E. A.; Wieman, C. E.
2008-09-26
We report on measurements of the excitation spectrum of a strongly interacting Bose-Einstein condensate. A magnetic-field Feshbach resonance is used to tune atom-atom interactions in the condensate and to reach a regime where quantum depletion and beyond mean-field corrections to the condensate chemical potential are significant. We use two-photon Bragg spectroscopy to probe the condensate excitation spectrum; our results demonstrate the onset of beyond mean-field effects in a gaseous Bose-Einstein condensate.
Bose-Einstein condensation in a two-component Bose gas with harmonic oscillator interaction
NASA Astrophysics Data System (ADS)
Abulseoud, A. A.; Abbas, A. H.; Galal, A. A.; El-Sherbini, Th M.
2016-07-01
In this article a system containing two species of identical bosons interacting via a harmonic oscillator potential is considered. It is assumed that the number of bosons of each species is the same and that bosons belonging to the same species repel each other while those belonging to different species attract. The Hamiltonian is diagonalized and the energy spectrum of the system is written down. The behaviour of the system in the thermodynamic limit is studied within the framework of the grand canonical ensemble, and thermodynamic parameters, such as the internal energy, entropy and specific heat capacity are calculated. It is shown that the system exhibits a single species Bose-Einstein condensation when the coupling strengths are equal and a dual species condensation when they are different.
Magnetic Dipolar Interaction in a Bose-Einstein Condensate Atomic Interferometer
Fattori, M.; Roati, G.; D'Errico, C.; Inguscio, M.; Modugno, G.; Deissler, B.; Zaccanti, M.; Jona-Lasinio, M.; Santos, L.
2008-11-07
We study the role played by the magnetic dipole interaction in the decoherence of a lattice-based interferometer that employs an alkali Bose-Einstein condensate with a tunable scattering length. The different behavior we observe for two different orientations of the dipoles gives us evidence of the anisotropic character of the interaction. The experiment is correctly reproduced by a model we develop only if the long-range interaction between different lattice sites is taken into account. Our model indicates that dipolar interaction can be compensated by a proper choice of the scattering length and that the magnetic dipole interaction should not represent an obstacle for atom interferometry with Bose-Einstein condensates with a tunable interaction.
Nearly-one-dimensional self-attractive Bose-Einstein condensates in optical lattices
Salasnich, L.; Toigo, F.; Cetoli, A.; Malomed, B. A.
2007-03-15
Within the framework of a mean-field description, we investigate atomic Bose-Einstein condensates, with attraction between atoms, under the action of a strong transverse confinement and periodic [optical-lattice (OL)] axial potential. Using a combination of the variational approximation, one-dimensional (1D) nonpolynomial Schroedinger equation, and direct numerical solutions of the underlying 3D Gross-Pitaevskii equation, we show that the ground state of the condensate is a soliton belonging to the semi-infinite band gap of the periodic potential. The soliton may be confined to a single cell of the lattice or extended to several cells, depending on the effective self-attraction strength g (which is proportional to the number of atoms bound in the soliton) and depth of the potential, V{sub 0}, the increase of V{sub 0} leading to strong compression of the soliton. We demonstrate that the OL is an effective tool to control the soliton's shape. It is found that, due to the 3D character of the underlying setting, the ground-state soliton collapses at a critical value of the strength, g=g{sub c}, which gradually decreases with the increase of V{sub 0}; under typical experimental conditions, the corresponding maximum number of {sup 7}Li atoms in the soliton, N{sub max}, ranges between 8000 and 4000. Examples of stable multipeaked solitons are also found in the first finite band gap of the lattice spectrum. The respective critical value g{sub c} again slowly decreases with the increase of V{sub 0}, corresponding to N{sub max}{approx_equal}5000.
NASA Astrophysics Data System (ADS)
Debnath, P. K.; Chakrabarti, Barnali
2010-10-01
We study the instability of collective excitations of a three-dimensional Bose-Einstein condensate with repulsive and attractive interactions in a shallow trap designed as a quadratic plus a quartic potential. By using a correlated many-body theory, we determine the excitation modes and probe the critical behavior of collective modes, having a crucial dependence on the anharmonic parameter. We examine the power-law behavior of monopole frequency near criticality. In Gross-Pitaevskii variational treatment [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.80.1576 80, 1576 (1998)] the power-law exponent is determined as one-fourth power of (1-(A)/(Acr)), A is the number of condensate atoms and Acr is the critical number near collapse. We observe that the power-law exponent becomes (1)/(6) in our calculation for the pure harmonic trap and it becomes (1)/(7), for traps with a small anharmonic distortion. However for large anharmonicity the power law breaks down.
Debnath, P. K.; Chakrabarti, Barnali
2010-10-15
We study the instability of collective excitations of a three-dimensional Bose-Einstein condensate with repulsive and attractive interactions in a shallow trap designed as a quadratic plus a quartic potential. By using a correlated many-body theory, we determine the excitation modes and probe the critical behavior of collective modes, having a crucial dependence on the anharmonic parameter. We examine the power-law behavior of monopole frequency near criticality. In Gross-Pitaevskii variational treatment [Phys. Rev. Lett. 80, 1576 (1998)] the power-law exponent is determined as one-fourth power of (1-(A/A{sub cr})), A is the number of condensate atoms and A{sub cr} is the critical number near collapse. We observe that the power-law exponent becomes (1/6) in our calculation for the pure harmonic trap and it becomes (1/7), for traps with a small anharmonic distortion. However for large anharmonicity the power law breaks down.
Interaction of a probe pulse with a 'dressed' Bose-Einstein condensate of rarefied atomic gases
Shamrov, N I
2008-01-31
Semiclassical equations describing the interaction of a probe pulse with a 'dressed' Bose-Einstein condensate of a rarefied atomic gas are proposed. The analytic solution of these equations is obtained for low-intensity pulses. The conditions of the appearance of a diffraction grating from recoil atoms are found. The existence of induced superradiance at the probe-beam frequency is predicted. The pulse propagation velocity in the condensate is determined as a function of its energy. The limits of the applicability of the two-level model of a 'dressed' atom are estimated. (nonlinear optical phenomena)
Interaction of half-quantized vortices in two-component Bose-Einstein condensates
Eto, Minoru; Kasamatsu, Kenichi; Nitta, Muneto; Takeuchi, Hiromitsu; Tsubota, Makoto
2011-06-15
We study the asymptotic interaction between two half-quantized vortices in two-component Bose-Einstein condensates. When two vortices in different components are placed at distance 2R, the leading order of the force between them is found to be (lnR/{xi}-1/2)/R{sup 3}, in contrast to 1/R between vortices placed in the same component. We derive it analytically using the Abrikosov ansatz and the profile functions of the vortices, confirmed numerically with the Gross-Pitaevskii model. We also find that the short-range cutoff of the intervortex potential linearly depends on the healing length.
An investigation of Bose-Einstein correlations in muon-nucleon interactions at 490 GeV
NASA Astrophysics Data System (ADS)
Adams, M. R.; Aïd, S.; Anthony, P. L.; Baker, M. D.; Bartlett, J.; Bhatti, A. A.; Botterweck, F.; Braun, H. M.; Busza, W.; Conrad, J. M.; Coutrakon, G.; Davisson, R.; Derado, I.; Dhawan, S. K.; Dougherty, W.; Dreyer, T.; Dziunikowska, K.; Eckardt, V.; Ecker, U.; Erdmann, M.; Eskreys, A.; Fang, G.; Figiel, J.; Gebauer, H. J.; Geesaman, D. F.; Gilman, R.; Green, M. C.; Haas, J.; Halliwell, C.; Hanlon, J.; Hantke, D.; Hughes, V. W.; Jackson, H. E.; Jaffe, D. E.; Jancso, G.; Jansen, D. M.; Kaufman, S.; Kennedy, R. D.; Kirk, T.; Kobrak, H. G. E.; Krzywdzinski, S.; Kunori, S.; Lord, J. J.; Lubatti, H. J.; McLeod, D.; Magill, S.; Malecki, P.; Manz, A.; Melanson, H.; Michael, D. G.; Mohr, W.; Montgomery, H. E.; Morfin, J. G.; Nickerson, R. B.; O'Day, S.; Olkiewicz, K.; Osborne, L.; Papavassiliou, V.; Pawlik, B.; Pipkin, F. M.; Ramberg, E. J.; Röser, A.; Ryan, J. J.; Salgado, C. W.; Salvarani, A.; Schellman, H.; Schmitt, M.; Schmitz, N.; Schüler, K. P.; Seyerlein, H. J.; Skuja, A.; Snow, G. A.; Söldner-Rembold, S.; Steinberg, P. H.; Stier, H. E.; Stopa, P.; Swanson, R. A.; Talaga, R.; Tentindo-Repond, S.; Trost, H.-J.; Venkataramania, H.; Wilhelm, M.; Wilkes, J.; Wilson, R.; Wittek, W.; Wolbers, S. A.; Zhao, T.; Fermilab E665 Collaboration
1993-07-01
An investigation of Bose-Einstein correlations amongst like-charged pions produced in muon-nucleon interactions at 490 GeV is presented. On top of a broader enhancement, a steep increase in the correlations at small four-momentum differences between the two pions is observed which may be explained by the contribution from decays of resonances (ϱ-mesons). A two-dimensional analysis discriminates between two different parametrizations of the Bose-Einstein effect, strongly favoring the Lorentz-invariant parametrization over a parametrization based on a Gaussian source distribution in space and time.
Bose-Einstein condensation of cesium.
Weber, Tino; Herbig, Jens; Mark, Michael; Nägerl, Hanns-Christoph; Grimm, Rudolf
2003-01-10
Bose-Einstein condensation of cesium atoms is achieved by evaporative cooling using optical trapping techniques. The ability to tune the interactions between the ultracold atoms by an external magnetic field is crucial to obtain the condensate and offers intriguing features for potential applications. We explore various regimes of condensate self-interaction (attractive, repulsive, and null interaction strength) and demonstrate properties of imploding, exploding, and non-interacting quantum matter. PMID:12471267
Spin-orbit coupled Bose-Einstein condensates with Rydberg-dressing interaction
NASA Astrophysics Data System (ADS)
Lü, Hao; Zhu, Shao-Bing; Qian, Jun; Wang, Yu-Zhu
2015-09-01
Interaction between Rydberg atoms can be used to control the properties of interatomic interaction in ultracold gases by weakly dressing the atoms with a Rydberg state. Here we investigate the effect of the Rydberg-dressing interaction on the ground-state properties of a Bose-Einstein condensate imposed by Raman-induced spin-orbit coupling. We find that, in the case of SU(2)-invariant s-wave interactions, the gas is only in the plane-wave phase and the zero-momentum phase is absent. In particular, we also predict an unexpected magnetic stripe phase composed of two plane-wave components with unequal weight when s-wave interactions are non-symmetric, which originates from the Rydberg-dressing interaction. Project supported by the National Basic Research Program of China (Grant No. 2011CB921504) and the National Natural Science Foundation of China (Grant No. 11104292).
Squeezing in the weakly interacting uniform Bose-Einstein condensate
Haque, Masudul; Ruckenstein, Andrei E.
2006-10-15
We investigate the presence of squeezing in the weakly repulsive uniform Bose gas, in both the condensate mode and in the nonzero opposite-momenta mode pairs, using two different variational formulations. We explore the U(1) symmetry breaking and Goldstone's theorem in the context of a squeezed coherent variational wave function and present the associated Ward identity. We show that squeezing of the condensate mode is absent at the mean field Hartree-Fock-Bogoliubov level and emerges as a result of fluctuations about mean field as a finite volume effect, which vanishes in the thermodynamic limit. On the other hand, the squeezing of the excitations about the condensate survives the thermodynamic limit and is interpreted in terms of density-phase variables using a number-conserving formulation of the interacting Bose gas.
Rayleigh surface wave interaction with the 2D exciton Bose-Einstein condensate
Boev, M. V.; Kovalev, V. M.
2015-06-15
We describe the interaction of a Rayleigh surface acoustic wave (SAW) traveling on the semiconductor substrate with the excitonic gas in a double quantum well located on the substrate surface. We study the SAW attenuation and its velocity renormalization due to the coupling to excitons. Both the deformation potential and piezoelectric mechanisms of the SAW-exciton interaction are considered. We focus on the frequency and excitonic density dependences of the SAW absorption coefficient and velocity renormalization at temperatures both above and well below the critical temperature of Bose-Einstein condensation of the excitonic gas. We demonstrate that the SAW attenuation and velocity renormalization are strongly different below and above the critical temperature.
Feedback control of an interacting Bose-Einstein condensate using phase-contrast imaging
NASA Astrophysics Data System (ADS)
Szigeti, S. S.; Hush, M. R.; Carvalho, A. R. R.; Hope, J. J.
2010-10-01
The linewidth of an atom laser is limited by density fluctuations in the Bose-Einstein condensate (BEC) from which the atom laser beam is outcoupled. In this paper we show that a stable spatial mode for an interacting BEC can be generated using a realistic control scheme that includes the effects of the measurement backaction. This model extends the feedback theory, based on a phase-contrast imaging setup, presented by Szigeti, Hush, Carvalho, and Hope [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.80.013614 80, 013614 (2009)]. In particular, it is applicable to a BEC with large interatomic interactions and solves the problem of inadequacy of the mean-field (coherent state) approximation by utilizing a fixed number state approximation. Our numerical analysis shows the control to be more effective for a condensate with a large nonlinearity.
Long-lived periodic revivals of coherence in an interacting Bose-Einstein condensate
Egorov, M.; Ivannikov, V.; Opanchuk, B.; Drummond, P.; Hall, B. V.; Sidorov, A. I.; Anderson, R. P.
2011-08-15
We observe the coherence of an interacting two-component Bose-Einstein condensate (BEC) surviving for seconds in a trapped Ramsey interferometer. Mean-field-driven collective oscillations of two components lead to periodic dephasing and rephasing of condensate wave functions with a slow decay of the interference fringe visibility. We apply spin echo synchronous with the self-rephasing of the condensate to reduce the influence of state-dependent atom losses, significantly enhancing the visibility up to 0.75 at the evolution time of 1.5 s. Mean-field theory consistently predicts higher visibility than experimentally observed values. We quantify the effects of classical and quantum noise and infer a coherence time of 2.8 s for a trapped condensate of 5.5x10{sup 4} interacting atoms.
Weakly interacting spinor Bose-Einstein condensates with three-dimensional spin-orbit coupling
NASA Astrophysics Data System (ADS)
Shu-Wei, Song; Rui, Sun; Hong, Zhao; Xuan, Wang; Bao-Zhong, Han
2016-04-01
Starting from the Hamiltonian of the second quantization form, the weakly interacting Bose-Einstein condensate with spin-orbit coupling of Weyl type is investigated. It is found that the SU(2) nonsymmetric term, i.e., the spin-dependent interaction, can lift the degeneracy of the ground states with respect to the z component of the total angular momentum J z , casting the ground condensate state into a configuration of zero J z . This ground state density profile can also be affirmed by minimizing the full Gross-Pitaevskii energy functional. The spin texture of the zero J z state indicates that it is a knot structure, whose fundamental group is π 3(M) ≅ π 3(S 2) = Z. Project supported by the National Natural Science Foundation of China (Grant No. 11447178).
Vortex formation in a fast rotating Bose-Einstein condensate
Ghosh, Tarun Kanti
2004-04-01
We study rotational motion of an interacting atomic Bose-Einstein condensate confined in a quadratic-plus-quartic potential. We calculate the lowest energy surface mode frequency and show that a symmetric trapped (harmonic and quartic) Bose-Einstein condensate breaks the rotational symmetry of the Hamiltonian when rotational frequency is greater than one-half of the lowest energy surface mode frequency. We argue that the formation of a vortex is not possible in a noninteracting as well as in an attractive Bose-Einstein condensate confined in a harmonic trap due to the absence of the spontaneous shape deformation, but it can occur which leads to the vortex formation if we add an additional quartic potential. Moreover, the spontaneous shape deformation and consequently the formation of a vortex in an attractive system depends on the strengths of the two-body interaction and the quartic potential.
{sup 85}Rb tunable-interaction Bose-Einstein condensate machine
Altin, P. A.; Robins, N. P.; Doering, D.; Debs, J. E.; Poldy, R.; Figl, C.; Close, J. D.
2010-06-15
We describe our experimental setup for creating stable Bose-Einstein condensates (BECs) of {sup 85}Rb with tunable interparticle interactions. We use sympathetic cooling with {sup 87}Rb in two stages, initially in a tight Ioffe-Pritchard magnetic trap and subsequently in a weak, large-volume, crossed optical dipole trap, using the 155 G Feshbach resonance to manipulate the elastic and inelastic scattering properties of the {sup 85}Rb atoms. Typical {sup 85}Rb condensates contain 4x10{sup 4} atoms with a scattering length of a=+200a{sub 0}. Many aspects of the design presented here could be adapted to other dual-species BEC machines, including those involving degenerate Fermi-Bose mixtures. Our minimalist apparatus is well suited to experiments on dual-species and spinor Rb condensates, and has several simplifications over the {sup 85}Rb BEC machine at JILA, which we discuss at the end of this article.
Competing interactions in population-imbalanced two-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Galteland, Peder Notto; Sudbø, Asle
2016-08-01
We consider a two-component Bose-Einstein condensate with and without synthetic "spin-orbit" interactions in two dimensions. Density and phase fluctuations of the condensate are included, allowing us to study the impact of thermal fluctuations and density-density interactions on the physics originating with spin-orbit interactions. In the absence of spin-orbit interactions, we find that intercomponent density interactions deplete the minority condensate. The thermally driven phase transition is driven by coupled density and phase-fluctuations, but is nevertheless shown to be a phase-transition in the Kosterlitz-Thouless universality class with close to universal amplitude ratios irrespective of whether both the minority- and majority condensates exist in the ground state, or only one condensate exists. In the presence of spin-orbit interactions we observe three separate phases, depending on the strength of the spin-orbit coupling and intercomponent density-density interactions: a phase-modulated phase with uniform amplitudes for small intercomponent interactions, a completely imbalanced, effectively single-component condensate for intermediate spin-orbit coupling strength and sufficiently large intercomponent interactions, and a phase-modulated and amplitude-modulated phase for sufficiently large values of both the spin-orbit coupling and the intercomponent density-density interactions. The phase that is modulated by a single q -vector only is observed to transition into an isotropic liquid through a strong depinning transition with periodic boundary conditions, which weakens with open boundaries.
Rau, Stefan; Main, Joerg; Wunner, Guenter
2010-08-15
The variational method of coupled Gaussian functions is applied to Bose-Einstein condensates with long-range interactions. The time dependence of the condensate is described by dynamical equations for the variational parameters. We present the method and analytically derive the dynamical equations from the time-dependent Gross-Pitaevskii equation. The stability of the solutions is investigated using methods of nonlinear dynamics. The concept presented in this article will be applied to Bose-Einstein condensates with monopolar 1/r and dipolar 1/r{sup 3} interaction in the subsequent article [S. Rau et al., Phys. Rev. A 82, 023611 (2010)], where we will present a wealth of phenomena obtained using the ansatz with coupled Gaussian functions.
Matter wave switching in Bose-Einstein condensates via intensity redistribution soliton interactions
Rajendran, S.; Lakshmanan, M.; Muruganandam, P.
2011-02-15
Using time dependent nonlinear (s-wave scattering length) coupling between the components of a weakly interacting two component Bose-Einstein condensate (BEC), we show the possibility of matter wave switching (fraction of atoms transfer) between the components via shape changing/intensity redistribution (matter redistribution) soliton interactions. We investigate the exact bright-bright N-soliton solution of an effective one-dimensional (1D) two component BEC by suitably tailoring the trap potential, atomic scattering length, and atom gain or loss. In particular, we show that the effective 1D coupled Gross-Pitaevskii equations with time dependent parameters can be transformed into the well known completely integrable Manakov model described by coupled nonlinear Schroedinger equations by effecting a change of variables of the coordinates and the wave functions under certain conditions related to the time dependent parameters. We obtain the one-soliton solution and demonstrate the shape changing/matter redistribution interactions of two and three-soliton solutions for the time-independent expulsive harmonic trap potential, periodically modulated harmonic trap potential, and kinklike modulated harmonic trap potential. The standard elastic collision of solitons occur only for a specific choice of soliton parameters.
Cheng Yongshan; Adhikari, S. K.
2010-02-15
By direct numerical simulation of the time-dependent Gross-Pitaevskii equation using the split-step Fourier spectral method, we study different aspects of the localization of a cigar-shaped interacting binary (two-component) Bose-Einstein condensate (BEC) in a one-dimensional bichromatic quasiperiodic optical-lattice potential, as used in a recent experiment on the localization of a BEC [Roati et al., Nature 453, 895 (2008)]. We consider two types of localized states: (i) when both localized components have a maximum of density at the origin x=0, and (ii) when the first component has a maximum of density and the second a minimum of density at x=0. In the noninteracting case, the density profiles are symmetric around x=0. We numerically study the breakdown of this symmetry due to interspecies and intraspecies interactions acting on the two components. Where possible, we have compared the numerical results with a time-dependent variational analysis. We also demonstrate the stability of the localized symmetry-broken BEC states under small perturbation.
Interacting spin-orbit-coupled spin-1 Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Sun, Kuei; Qu, Chunlei; Xu, Yong; Zhang, Yongping; Zhang, Chuanwei
2016-02-01
The recent experimental realization of spin-orbit (SO) coupling for spin-1 ultracold atoms opens an interesting avenue for exploring SO-coupling-related physics in large-spin systems, which is generally unattainable in electronic materials. In this paper, we study the effects of interactions between atoms on the ground states and collective excitations of SO-coupled spin-1 Bose-Einstein condensates (BECs) in the presence of a spin-tensor potential. We find that ferromagnetic interaction between atoms can induce a stripe phase exhibiting in-phase or out-of-phase modulating patterns between spin-tensor and zero-spin-component density waves. We characterize the phase transitions between different phases using the spin-tensor density as well as the collective dipole motion of the BEC. We show that there exists a double maxon-roton structure in the Bogoliubov-excitation spectrum, attributed to the three band minima of the SO-coupled spin-1 BEC.
Reservoir interactions of a vortex in a trapped three-dimensional Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Rooney, S. J.; Allen, A. J.; Zülicke, U.; Proukakis, N. P.; Bradley, A. S.
2016-06-01
We simulate the dissipative evolution of a vortex in a trapped finite-temperature dilute-gas Bose-Einstein condensate using first-principles open-systems theory. Simulations of the complete stochastic projected Gross-Pitaevskii equation for a partially condensed Bose gas containing a single quantum vortex show that the transfer of condensate energy to the incoherent thermal component without population transfer provides an important channel for vortex decay. For the lower temperatures considered, this effect is significantly larger that the population transfer process underpinning the standard theory of vortex decay, and is the dominant determinant of the vortex lifetime. A comparison with the Zaremba-Nikuni-Griffin kinetic (two-fluid) theory further elucidates the role of the particle transfer interaction, and suggests the need for experimental testing of reservoir interaction theory. The dominance of this particular energetic decay mechanism for this open quantum system should be testable with current experimental setups, and its observation would have broad implications for the dynamics of atomic matter waves and experimental studies of dissipative phenomena.
Sakaguchi, Hidetsugu; Li, Ben; Malomed, Boris A
2014-03-01
It is commonly known that two-dimensional mean-field models of optical and matter waves with cubic self-attraction cannot produce stable solitons in free space because of the occurrence of collapse in the same setting. By means of numerical analysis and variational approximation, we demonstrate that the two-component model of the Bose-Einstein condensate with the spin-orbit Rashba coupling and cubic attractive interactions gives rise to solitary-vortex complexes of two types: semivortices (SVs, with a vortex in one component and a fundamental soliton in the other), and mixed modes (MMs, with topological charges 0 and ±1 mixed in both components). These two-dimensional composite modes can be created using the trapping harmonic-oscillator (HO) potential, but remain stable in free space, if the trap is gradually removed. The SVs and MMs realize the ground state of the system, provided that the self-attraction in the two components is, respectively, stronger or weaker than the cross attraction between them. The SVs and MMs which are not the ground states are subject to a drift instability. In free space (in the absence of the HO trap), modes of both types degenerate into unstable Townes solitons when their norms attain the respective critical values, while there is no lower existence threshold for the stable modes. Moving free-space stable solitons are also found in the present non-Galilean-invariant system, up to a critical velocity. Collisions between two moving solitons lead to their merger into a single one.
Nonlinear vortex-phonon interactions in a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Mendonça, J. T.; Haas, F.; Gammal, A.
2016-07-01
We consider the nonlinear coupling between an exact vortex solution in a Bose-Einstein condensate and a spectrum of elementary excitations in the medium. These excitations, or Bogoliubov-de Gennes modes, are indeed a special kind of phonons. We treat the spectrum of elementary excitations in the medium as a gas of quantum particles, sometimes also called bogolons. An exact kinetic equation for the bogolon gas is derived, and an approximate form of this equation, valid in the quasi-classical limit, is also obtained. We study the energy transfer between the vortex and the bogolon gas, and establish conditions for vortex instability and damping.
NASA Astrophysics Data System (ADS)
Dalafi, A.; Naderi, M. H.
2016-07-01
We present a theoretical study of the phase noise, intensity and quadrature squeezing power spectra of the transmitted field of a driven optical cavity containing an interacting one-dimensional Bose-Einstein condensate. We show how the pattern of the output power spectrum of the cavity changes due to the nonlinear effect of atomic collisions. Furthermore, it is shown that due to a one-to-one correspondence between the splitting of the peaks in the phase noise power spectrum of the cavity output field and the s-wave scattering frequency of the atom-atom interaction, one can measure the strength of interatomic interaction. In addition, we show how the atomic collisions affect the squeezing behavior of the output field.
NASA Astrophysics Data System (ADS)
McDonald, R. G.; Bradley, A. S.
2015-09-01
As a test of the Kibble-Zurek mechanism (KZM) of defect formation, we simulate the Bose-Einstein condensation transition in a toroidally confined Bose gas by using the stochastic projected Gross-Pitaevskii equation, with and without the energy-damping reservoir interaction. Energy-damping alters the scaling of the winding-number distribution with the quench time—a departure from the universal KZM theory that relies on equilibrium critical exponents. Numerical values are obtained for the correlation-length critical exponent ν and the dynamical critical exponent z for each variant of reservoir interaction theory. The energy-damping reservoir interactions cause significant modification of the dynamical critical exponent of the phase transition, while preserving the essential KZM critical scaling behavior. Comparison of numerical and analytical two-point correlation functions further illustrates the effect of energy damping on the correlation length during freeze-out.
Rezende, Sergio M.
2009-05-01
Strong experimental evidences of the formation of quasiequilibrium Bose-Einstein condensation (BEC) of magnons at room temperature in a film of yttrium iron garnet (YIG) excited by microwave radiation have been recently reported. Here we present a theory for the dynamics of the magnon gas driven by a microwave field far out of equilibrium that provides rigorous support for the formation of a BEC of magnons in a YIG film magnetized in the plane. We show that if the microwave driving power exceeds a threshold value the nonlinear magnetic interactions create cooperative mechanisms for the onset of a phase transition leading to the spontaneous generation of quantum coherence and magnetic dynamic order in a macroscopic scale. The theoretical results agree with the experimental data for the intensity and the decay rate of the Brillouin light scattering from the BEC as a function of power and for the microwave emission from the uniform mode generated by the confluence of BEC magnon pairs.
Chaotic behavior of three interacting vortices in a confined Bose-Einstein condensate
Kyriakopoulos, Nikos; Koukouloyannis, Vassilis; Skokos, Charalampos; Kevrekidis, Panayotis G.
2014-06-01
Motivated by recent experimental works, we investigate a system of vortex dynamics in an atomic Bose-Einstein condensate (BEC), consisting of three vortices, two of which have the same charge. These vortices are modeled as a system of point particles which possesses a Hamiltonian structure. This tripole system constitutes a prototypical model of vortices in BECs exhibiting chaos. By using the angular momentum integral of motion, we reduce the study of the system to the investigation of a two degree of freedom Hamiltonian model and acquire quantitative results about its chaotic behavior. Our investigation tool is the construction of scan maps by using the Smaller ALignment Index as a chaos indicator. Applying this approach to a large number of initial conditions, we manage to accurately and efficiently measure the extent of chaos in the model and its dependence on physically important parameters like the energy and the angular momentum of the system.
Soliton resonance in bose-einstein condensate
NASA Technical Reports Server (NTRS)
Zak, Michail; Kulikov, I.
2002-01-01
A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.
Topological objects in two-component Bose-Einstein condensates
Cho, Y. M.; Khim, Hyojoong; Zhang, Pengming
2005-12-15
We study the topological objects in two-component Bose-Einstein condensates. We compare two competing theories of two-component Bose-Einstein condensates, the popular Gross-Pitaevskii theory, and the recently proposed gauge theory of two-component Bose-Einstein condensate which has an induced vorticity interaction. We show that two theories produce very similar topological objects, in spite of the obvious differences in dynamics. Furthermore we show that the gauge theory of two-component Bose-Einstein condensates, with the U(1) gauge symmetry, is remarkably similar to the Skyrme theory. Just like the Skyrme theory this theory admits the non-Abelian vortex, the helical vortex, and the vorticity knot. We construct the lightest knot solution in two-component Bose-Einstein condensates numerically, and discuss how the knot can be constructed in the spin-(1/2) condensate of {sup 87}Rb atoms.
NASA Astrophysics Data System (ADS)
Chavanis, Pierre-Henri
2011-08-01
We provide an approximate analytical expression of the mass-radius relation of a Newtonian self-gravitating Bose-Einstein condensate (BEC) with short-range interactions described by the Gross-Pitaevskii-Poisson system. These equations model astrophysical objects such as boson stars and, presumably, dark matter galactic halos. Our study connects the noninteracting case studied by Ruffini and Bonazzola (1969) to the Thomas-Fermi limit studied by Böhmer and Harko (2007). For repulsive short-range interactions (positive scattering lengths), there exists configurations of arbitrary mass but their radius is always larger than a minimum value. For attractive short-range interactions (negative scattering lengths), equilibrium configurations only exist below a maximum mass. Above that mass, the system is expected to collapse and form a black hole. We also study the radius versus scattering length relation for a given mass. We find that equilibrium configurations only exist above a (negative) minimum scattering length. Our approximate analytical solution, based on a Gaussian ansatz, provides a very good agreement with the exact solution obtained by numerically solving a nonlinear differential equation representing hydrostatic equilibrium. Our analytical treatment is, however, easier to handle and permits one to study the stability problem, and derive an expression of the pulsation period, by developing an analogy with a simple mechanical problem.
NASA Astrophysics Data System (ADS)
Nakamura, Katsuhiro; Babajanov, Doniyor; Matrasulov, Davron; Kobayashi, Michikazu; Muruganandam, Paulsamy
2016-08-01
With use of a variational principle, we investigate a role of breathing width degree of freedom in the effective theory of interacting vortices in a trapped single-component Bose-Einstein condensates in two dimensions, under strong repulsive cubic nonlinearity. For the trial function, we choose a product of two vortex functions, assuming a pair interaction, and employ the amplitude form of each vortex function in the Padé approximation, which accommodates a hallmark of the vortex core. We obtain the Lagrange equation for the interacting vortex-core coordinates coupled with the time-derivative of width and also its Hamilton formalism by having recourse to a non-standard Poisson bracket. By solving the Hamilton equation, we find rapid radial breathing oscillations superposed on the slower rotational motion of vortex cores, consistent with numerical solutions of the Gross-Pitaevskii equation. In higher-energy states of two vortex systems, the breathing width degree of freedom plays the role of a kicking in the kicked rotator, and generates chaos with a structure of sea-urchin needles. The by-products of the present variational approach include: (1) the charge-dependent logarithmic inter-vortex interaction multiplied with a pre-factor, which depends on the scalar product of a pair of core-position vectors; (2) the charge-independent short-range repulsive inter-vortex interaction and spring force.
NASA Astrophysics Data System (ADS)
Sun, Kuei; Qu, Chunlei; Xu, Yong; Zhang, Yongping; Zhang, Chuanwei
Spin-orbit (SO) coupling plays a major role in many important phenomena in condensed matter physics. However, the SO coupling physics in high-spin systems, especially with superfluids, has not been well explored because of the spin half of electrons in solids. In this context, the recent experimental realization of spin-orbit coupling in spin-1 Bose-Einstein condensates (BECs) has opened a completely new avenue for exploring SO-coupled high-spin superfluids. Nevertheless, the experiment has only revealed the single-particle physics of the system. Here, we study the effects of interactions between atoms on the ground states and collective excitations of SO-coupled spin-1 BECs in the presence of a spin-tensor potential. We find that ferromagnetic interaction between atoms can induce a stripe phase exhibiting two modulating patterns. We characterize the phase transitions between different phases using the spin-tensor density as well as the collective dipole motion of the BEC. We show that there exists a new type of double maxon-roton structure in the Bogoliubov-excitation spectrum, attributing to the three band minima of the SO-coupled spin-1 BEC. Our work could motivate further theoretical and experimental study along this direction.
El-Sherbini, Th.M.
2005-03-17
This article gives a brief review of Bose-Einstein condensation. It is an exotic quantum phenomenon that was observed in dilute atomic gases for the first time in 1995. It exhibits a new state of matter in which a group of atoms behaves as a single particle. Experiments on this form of matter are relevant to many different areas of physics- from atomic clocks and quantum computing to super fluidity, superconductivity and quantum phase transition.
NASA Astrophysics Data System (ADS)
Bhowmik, Anal; Mondal, Pradip Kumar; Majumder, Sonjoy; Deb, Bimalendu
2016-06-01
The exchange of orbital angular momentum (OAM) between paraxial optical vortex and a Bose-Einstein condensate (BEC) of atomic gases is well known. In this paper, we develop a theory for the microscopic interaction between matter and an optical vortex beyond paraxial approximation. We show how superposition of vortex states of BEC can be created with a focused optical vortex. Since the polarization or spin angular momentum (SAM) of the optical field is coupled with OAM of the field, in this case, these angular momenta can be transferred to the internal electronic and external center-of-mass motion of atoms provided both the motions are coupled. We propose a scheme for producing the superposition of matter-wave vortices using Gaussian and a focused Laguerre-Gaussian beam. We study how two-photon Rabi frequencies of stimulated Raman transitions vary with focusing angles for different combinations of OAM and SAM of optical states. We demonstrate the formation of vortex-antivortex structure and discuss interference of three vortex states in a BEC.
Accurate control of a Bose-Einstein condensate by managing the atomic interaction
Morales-Molina, L.; Arevalo, E.
2010-07-15
We exploit the variation of the atomic interaction in order to move ultracold atoms with attractive interaction across an ac-driven periodic lattice. By breaking relevant symmetries, a gathering of atoms is achieved. Accurate control of the gathered atoms' positions can be demonstrated via the control of the atomic localization process. The localization process is analyzed with the help of the nonlinear Floquet states where the Landau-Zener tunneling between states is observed and controlled. Transport effects in the presence of disorder are discussed.
Liu Zhao; Guo Hongli; Fan Heng; Vedral, Vlatko
2011-01-15
We use entanglement to investigate the transition from vortex-liquid phase to vortex-lattice phase in a weakly interacting rotating Bose-Einstein condensate. For the torus geometry, the ground-state entanglement spectrum is analyzed to distinguish these two phases. The low-lying part of the ground-state entanglement spectrum, as well as the behavior of its lowest level, changes clearly when the transition occurs. For the sphere geometry, the entanglement gap in the conformal limit is also studied. We also show that the decrease in entanglement between particles can be regarded as a signal of the transition.
Bose-Einstein condensation of dilute atomic gases
NASA Astrophysics Data System (ADS)
Wu, Biao
The Bose-Einstein condensation of dilute atomic gases is studied. The focus is on the interesting properties and the dynamical behavior of Bose-Einstein condensates (BECs1) under various external manipulations. We investigate how the interaction affects the interference pattern between two BEC clouds, and show how the interference pattern can be calculated. We then present a theory on the generation of dark solitons in BECs with a new experimental technique called phase imprint. By mapping this problem into a classic pendulum problem, we show how to design the phase step imprinted on a BEC cloud to generate desired dark solitons. We finally study the system of a BEC in an optical lattice, a nonlinear periodic system, which exhibits interesting new effects on the tunneling and superfluidity in terms of its Bloch bands and Bloch waves. 1In the dissertation, BEC stands for Bose-Einstein condensate, not Bose-Einstein condensation.
Vortex dynamics in cubic-quintic Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Mithun, T.; Porsezian, K.; Dey, Bishwajyoti
2013-07-01
We study vortex dynamics in a trapped Bose-Einstein condensate with tunable two- and three-body interactions. The dynamics is governed by two-dimensional cubic-quintic Gross-Pitaevskii equation. A time-dependent variational method has been used to obtain critical rotational frequency and surface mode frequency analytically and are compared with numerical simulation results. An imaginary time propagation method and Crank-Nicolson scheme for discretization have been used for numerical simulation. The numerically calculated average value of the angular momentum per particle shows very clearly its dynamical relation with the time development of the vortex formation. The rotational frequency dependence of the variation of average value of the angular momentum per particle with time shows that vortices form much faster in time for higher rotational frequency. Similarly, the vortex forms much faster in time with an increase of the strength of the repulsive three-body interaction. The simulation of the vortex lattice formation in the condensate shows that the presence of the three-body interactions does not alter the vortex lattice pattern but it helps in the shape deformations of the condensate thereby leading to vortex lattice formation. Likewise, the three-body interactions enable the vortex lattice formation in Bose-Einstein condensates even with attractive two-body interactions and in purely quintic BEC.
NASA Astrophysics Data System (ADS)
Kasamatsu, Kenichi; Eto, Minoru; Nitta, Muneto
2016-01-01
We study the interaction and dynamics of two half-quantized vortices in two-component Bose-Einstein condensates. Using the Padé approximation for the vortex core profile, we calculate the intervortex potential, whose asymptotic form for a large distance has been derived by Eto et al. [Phys. Rev. A 83, 063603 (2011), 10.1103/PhysRevA.83.063603]. Through numerical simulations of the two-dimensional Gross-Pitaevskii equations, we reveal different kinds of dynamical trajectories of the vortices depending on the combinations of signs of circulations and the intercomponent density coupling. Under the adiabatic limit, we derive the equations of motion for the vortex coordinates, in which the motion is caused by the balance between Magnus force and the intervortex forces. The initial velocity of the vortex motion can be explained quantitatively by this point vortex approximation, but understanding the long-time behavior of the dynamics needs more consideration beyond our model.
Bose-Einstein condensation of chromium.
Griesmaier, Axel; Werner, Jörg; Hensler, Sven; Stuhler, Jürgen; Pfau, Tilman
2005-04-29
We report on the generation of a Bose-Einstein condensate in a gas of chromium atoms, which have an exceptionally large magnetic dipole moment and therefore underlie anisotropic long-range interactions. The preparation of the chromium condensate requires novel cooling strategies that are adapted to its special electronic and magnetic properties. The final step to reach quantum degeneracy is forced evaporative cooling of 52Cr atoms within a crossed optical dipole trap. At a critical temperature of T(c) approximately 700 nK, we observe Bose-Einstein condensation by the appearance of a two-component velocity distribution. We are able to produce almost pure condensates with more than 50,000 condensed 52Cr atoms.
Axions: Bose Einstein condensate or classical field?
NASA Astrophysics Data System (ADS)
Davidson, Sacha
2015-05-01
The axion is a motivated dark matter candidate, so it would be interesting to find features in Large Scale Structures specific to axion dark matter. Such features were proposed for a Bose Einstein condensate of axions, leading to confusion in the literature (to which I contributed) about whether axions condense due to their gravitational interactions. This note argues that the Bose Einstein condensation of axions is a red herring: the axion dark matter produced by the misalignment mechanism is already a classical field, which has the distinctive features attributed to the axion condensate (BE condensates are described as classical fields). This note also estimates that the rate at which axion particles condense to the field, or the field evaporates to particles, is negligible.
Mach-Zehnder interferometry with interacting trapped Bose-Einstein condensates
Grond, Julian; Hohenester, Ulrich; Schmiedmayer, Joerg; Smerzi, Augusto
2011-08-15
We theoretically analyze a Mach-Zehnder interferometer with trapped condensates and find that it is surprisingly stable against the nonlinearity induced by interparticle interactions. The phase sensitivity, which we study for number-squeezed input states, can overcome the shot noise limit and be increased up to the Heisenberg limit provided that a Bayesian or maximum-likelihood phase estimation strategy is used. We finally demonstrate the robustness of the Mach-Zehnder interferometer in the presence of interactions against condensate oscillations and a realistic atom-counting error.
Spin-orbit coupled weakly interacting Bose-Einstein condensates in harmonic traps.
Hu, Hui; Ramachandhran, B; Pu, Han; Liu, Xia-Ji
2012-01-01
We investigate theoretically the phase diagram of a spin-orbit coupled Bose gas in two-dimensional harmonic traps. We show that at strong spin-orbit coupling the single-particle spectrum decomposes into different manifolds separated by ℏω{⊥}, where ω{⊥} is the trapping frequency. For a weakly interacting gas, quantum states with Skyrmion lattice patterns emerge spontaneously and preserve either parity symmetry or combined parity-time-reversal symmetry. These phases can be readily observed in a spin-orbit coupled gas of ^{87}Rb atoms in a highly oblate trap. PMID:22304247
Revivals in an attractive Bose-Einstein condensate in a double-well potential and their decoherence
Pawlowski, Krzysztof; Zin, Pawel; Rzazewski, Kazimierz; Trippenbach, Marek
2011-03-15
We study the dynamics of ultracold attractive atoms in a weakly linked two potential wells. We consider an unbalanced initial state and monitor dynamics of the population difference between the two wells. The average imbalance between wells undergoes damped oscillations, like in a classical counterpart, but then it revives almost to the initial value. We explain in detail the whole behavior using three different models of the system. Furthermore, we investigate the sensitivity of the revivals on the decoherence caused by one- and three-body losses. We include the dissipative processes using appropriate master equations and solve them using the stochastic wave approximation method.
Diquark Bose-Einstein condensation
Nawa, K.; Nakano, E.; Yabu, H.
2006-08-01
Bose-Einstein condensation of composite diquarks in quark matter (the color superconductor phase) is discussed using the quasichemical equilibrium theory at a relatively low-density region near the deconfinement phase transition, where dynamical quark-pair fluctuations are assumed to be described as bosonic degrees of freedom (diquarks). A general formulation is given for the diquark formation and particle-antiparticle pair-creation processes in the relativistic framework, and some interesting properties are shown, which are characteristic for the relativistic many-body system. Behaviors of transition temperature and phase diagram of the quark-diquark matter are generally presented in model parameter space, and their asymptotic behaviors are also discussed. As an application to the color superconductivity, the transition temperatures and the quark and diquark density profiles are calculated in case with constituent/current quarks, where the diquark is in the bound/resonant state. We obtained T{sub C}{approx}60-80 MeV for constituent quarks and T{sub C}{approx}130 MeV for current quarks at a moderate density ({rho}{sub b}{approx}3{rho}{sub 0}). The method is also developed to include interdiquark interactions into the quasichemical equilibrium theory within a mean-field approximation, and it is found that a possible repulsive diquark-diquark interaction lowers the transition temperature by {approx}50%.
Approaching Bose-Einstein Condensation
ERIC Educational Resources Information Center
Ferrari, Loris
2011-01-01
Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…
Rydberg Electrons in a Bose-Einstein Condensate.
Wang, Jia; Gacesa, Marko; Côté, R
2015-06-19
We investigate a hybrid system composed of ultracold Rydberg atoms immersed in an atomic Bose-Einstein condensate (BEC). The coupling between Rydberg electrons and BEC atoms leads to excitations of phonons, the exchange of which induces a Yukawa interaction between Rydberg atoms. Because of the small electron mass, the effective charge associated with this quasiparticle-mediated interaction can be large. Its range, equal to the BEC healing length, is tunable using Feshbach resonances to adjust the scattering length between BEC atoms. We find that for small healing lengths, the distortion of the BEC can "image" the Rydberg electron wave function, while for large healing lengths the induced attractive Yukawa potentials between Rydberg atoms are strong enough to bind them.
Entanglement Properties in Two-Component Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Jiang, Di-You
2016-10-01
We investigate entanglement inseparability and bipartite entanglement of in two-component Bose-Einstein condensate in the presence of the nonlinear interatomic interaction, interspecies interaction. Entanglement inseparability and bipartite entanglement have the similar properties. More entanglement can be generated by adjusting the nonlinear interatomic interaction and control the time interval of the entanglement by adjusting interspecies interaction.
Bose-Einstein condensation in complex networks.
Bianconi, G; Barabási, A L
2001-06-11
The evolution of many complex systems, including the World Wide Web, business, and citation networks, is encoded in the dynamic web describing the interactions between the system's constituents. Despite their irreversible and nonequilibrium nature these networks follow Bose statistics and can undergo Bose-Einstein condensation. Addressing the dynamical properties of these nonequilibrium systems within the framework of equilibrium quantum gases predicts that the "first-mover-advantage," "fit-get-rich," and "winner-takes-all" phenomena observed in competitive systems are thermodynamically distinct phases of the underlying evolving networks.
Bose-Einstein condensation of sodium atoms
NASA Astrophysics Data System (ADS)
Mewes, Marc-Oliver
1997-10-01
Bose-Einstein Condensation in an ultracold gas of neutral sodium atoms has been observed and studied. This was achieved utilizing a combination of laser cooling techniques, magnetic trapping and evaporative cooling. A novel tightly confining dc magnetic trap was developed and demonstrated. This trap combines tight confinement with excellent optical access. Evaporative cooling in this trap produced Bose condensates of 5× 106 atoms, a tenfold improvement over previous results. The Bose-Einstein phase transition was studied and characterized by mapping out the condensed fraction as a function of temperature across the transition point. The characteristic mean-field interaction of particles in the condensate was investigated. Collective excitations of a dilute Bose condensate have been observed. These excitations are analogous to phonons in superfluid helium. The frequencies of the lowest modes were studied for a temperature close to 0 K and compared with theoretical predictions based on mean-field theory. The characteristic damping of one of the modes was measured and compared to damping of 'sound waves' in an ultra-cold gas above the Bose-Einstein transition. We have also demonstrated an output coupler for Bose condensed atoms in a magnetic trap. With short rf pulses Bose condensates were put into a superposition of trapped and untrapped hyperfine states. By varying the rf amplitude we could adjust the fraction of outcoupled atoms between 0 and 100%. This source produces pulses of coherent atoms and can be regarded as a pulsed 'atom laser'. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)
Interference of Bose-Einstein condensates.
Band, Y B
2008-12-18
A formalism for describing the coherence and interference properties of two atomic clouds of Bose-Einstein condensates (BEC) is presented, which is applicable even in the opposite limits when the BEC clouds are initially coherent and when they are initially independent. First, we develop a mean-field theory wherein one mean-field mode is used, and then, for fragmented (i.e., independent) condensates, we use a mean-field theory with two modes. We then develop a full two-mode field theory, with a field operator composed of a sum of two terms containing matter wave mode functions phi1 and phi2, that multiply the destruction operators of the modes, a1 and a2. When atom-atom interactions are present and when the mode functions overlap, the matter wave mode functions phi1 and phi2 develop components moving to the right and left, and this results in interference fringes in the density. At the many-body level, another source of interference arises from expectation values of the form (a(i)+a(j)) with i double dagger j, which become nonzero due to tunneling and interactions. We detail how these two sources of interference affect the density profile and the density-density correlation functions of Bose-Einstein condensates in the coherent and in the fragmented regimes.
NASA Astrophysics Data System (ADS)
Vasilevskiy, Mikhail I.; Santiago-Pérez, Darío G.; Trallero-Giner, Carlos; Peres, Nuno M. R.; Kavokin, Alexey
2015-12-01
Exciton-polariton modes arising from interaction between bound excitons in monolayer thin semiconductor sheets and photons in a Fabry-Perot microcavity are considered theoretically. We calculate the dispersion curves, mode lifetimes, Rabi splitting, and Hopfield coefficients of these structures for two nearly 2D semiconductor materials, MoS2 and WS2, and suggest that they are interesting for studying the rich physics associated with the Bose-Einstein condensation of exciton polaritons. The large exciton binding energy and dipole allowed exciton transitions, in addition to the relatively easily controllable distance between the semiconductor sheets, are the advantages of this system in comparison with traditional GaAs or CdTe based semiconductor microcavities. In particular, in order to mimic the rich physical properties of the quantum degenerate mixture of two bosonic species of dilute atomic gases with tunable interspecies interaction, we put forward a structure containing two semiconductor sheets separated by some atomic-scale distance (l ) using a nearly 2D dielectric (e.g., h-BN), which offers the possibility of tuning the interaction between two exciton-polariton Bose-Enstein condensates. We show that the dynamics of this structure are ruled by two coupled Gross-Pitaevskii equations with the coupling parameter ˜l-1 .
Trapped fermions with density imbalance in the Bose-Einstein condensate limit.
Pieri, P; Strinati, G C
2006-04-21
We analyze the effects of imbalancing the populations of two-component trapped fermions, in the Bose-Einstein condensate limit of the attractive interaction between different fermions. Starting from the gap equation with two fermionic chemical potentials, we derive a set of coupled equations that describe composite bosons and excess fermions. We include in these equations the processes leading to the correct dimer-dimer and dimer-fermion scattering lengths. The coupled equations are then solved in the Thomas-Fermi approximation to obtain the density profiles for composite bosons and excess fermions, which are relevant to the recent experiments with trapped fermionic atoms.
Chaos control of a Bose-Einstein condensate in a moving optical lattice
NASA Astrophysics Data System (ADS)
Zhang, Zhiying; Feng, Xiuqin; Yao, Zhihai
2016-07-01
Chaos control of a Bose-Einstein condensate (BEC) loaded into a moving optical lattice with attractive interaction is investigated on the basis of Lyapunov stability theory. Three methods are designed to control chaos in BEC. As a controller, a bias constant, periodic force, or wavelet function feedback is added to the BEC system. Numerical simulations reveal that chaotic behavior can be well controlled to achieve periodicity by regulating control parameters. Different periodic orbits are available for different control parameters only if the maximal Lyapunov exponent of the system is negative. The abundant effect of chaotic control is also demonstrated numerically. Chaos control can be realized effectively by using our proposed control strategies.
Steady-state entanglement of a Bose-Einstein condensate and a nanomechanical resonator
Asjad, Muhammad; Saif, Farhan
2011-09-15
We analyze the steady-state entanglement between Bose-Einstein condensate trapped inside an optical cavity with a moving end mirror (nanomechanical resonator) driven by a single mode laser. The quantized laser field mediates the interaction between the Bose-Einstein condensate and nanomechanical resonator. In particular, we study the influence of temperature on the entanglement of the coupled system, and note that the steady-state entanglement is fragile with respect to temperature.
Controllable scattering of vector Bose-Einstein solitons
Babarro, Judit; Paz-Alonso, Maria J.; Michinel, Humberto; Salgueiro, Jose R.; Olivieri, David N.
2005-04-01
We show the possibility of producing matter-wave switching devices by using Manakov interactions between vector matter-wave solitons using two-species Bose-Einstein condensates (BECs). Our results establish the experimental parameters for three interaction regimes in two-species BECs: symmetric and asymmetric splitting, down-switching, and up-switching. We have studied the dependence upon the initial conditions and the kind of interaction between the two matter-wave solitons.
Probing of the optical properties of Bose-Einstein condensates.
NASA Astrophysics Data System (ADS)
Vestergaard Hau, Lene
1998-05-01
Interactions between photons and Bose-Einstein condensates are studied experimentally and theoretically. Our goal is to get a detailed understanding of the interactions themselves as well as to develop tools for probing Bose condensates. We routinely create million atom condensates of sodium in the '4D' magnetic bottle by using a combination of laser and evaporative cooling. We have used absorption of near resonant laser light to image condensate wavefunctions directly in the magnetic botttle. The method is sensitive to details of the wavefunction, in particular to the condensate surface. This is of importance, for example, in studies of interactions between condensates and thermal clouds at temperatures close to the transition temperature for Bose-Einstein condensation.
Recent developments in Bose-Einstein condensation
Kalman, G.
1997-09-22
This paper contains viewgraphs on developments on Bose-Einstein condensation. Some topics covered are: strongly coupled coulomb systems; standard response functions of the first and second kind; dynamical mean field theory; quasi localized charge approximation; and the main equations.
Scalar field as a Bose-Einstein condensate?
NASA Astrophysics Data System (ADS)
Castellanos, Elías; Escamilla-Rivera, Celia; Macías, Alfredo; Núñez, Darío
2014-11-01
We discuss the analogy between a classical scalar field with a self-interacting potential, in a curved spacetime described by a quasi-bounded state, and a trapped Bose-Einstein condensate. In this context, we compare the Klein-Gordon equation with the Gross-Pitaevskii equation. Moreover, the introduction of a curved background spacetime endows, in a natural way, an equivalence to the Gross-Pitaevskii equation with an explicit confinement potential. The curvature also induces a position dependent self-interaction parameter. We exploit this analogy by means of the Thomas-Fermi approximation, commonly used to describe the Bose-Einstein condensate, in order to analyze the quasi bound scalar field distribution surrounding a black hole.
Anisotropic Solitons in Dipolar Bose-Einstein Condensates
Tikhonenkov, I.; Vardi, A.; Malomed, B. A.
2008-03-07
Starting with a Gaussian variational ansatz, we predict anisotropic bright solitons in quasi-2D Bose-Einstein condensates consisting of atoms with dipole moments polarized perpendicular to the confinement direction. Unlike isotropic solitons predicted for the moments aligned with the confinement axis [Phys. Rev. Lett. 95, 200404 (2005)], no sign reversal of the dipole-dipole interaction is necessary to support the solitons. Direct 3D simulations confirm their stability.
Spin Echo in Spinor Dipolar Bose-Einstein Condensates
Yasunaga, Masashi; Tsubota, Makoto
2008-11-28
We theoretically propose and numerically realize spin echo in a spinor Bose-Einstein condensate (BEC). We investigate the influence on the spin echo of phase separation of the condensate. The equation of motion of the spin density exhibits two relaxation times. We use two methods to separate the relaxation times and hence demonstrate a technique to reveal magnetic dipole-dipole interactions in spinor BECs.
Dipolar Bose-Einstein condensates with weak disorder
Krumnow, Christian; Pelster, Axel
2011-08-15
A homogeneous polarized dipolar Bose-Einstein condensate is considered in the presence of weak quenched disorder within mean-field theory at zero temperature. By first solving perturbatively the underlying Gross-Pitaevskii equation and then performing disorder ensemble averages for physical observables, it is shown that the anisotropy of the two-particle interaction is passed on to both the superfluid density and the sound velocity.
Bose-Einstein-condensate interferometer with macroscopic arm separation
Garcia, O.; Deissler, B.; Hughes, K. J.; Reeves, J. M.; Sackett, C. A.
2006-09-15
A Michelson interferometer using Bose-Einstein condensates is demonstrated with coherence times of up to 44 ms and arm separations up to 180 {mu}m. This arm separation is larger than that observed for any previous atom interferometer. The device uses atoms weakly confined in a magnetic guide and the atomic motion is controlled using Bragg interactions with an off-resonant standing-wave laser beam.
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
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.
Kamchatnov, A M; Kartashov, Y V
2013-10-01
We predict that oblique breathers can be generated by a flow of two-component Bose-Einstein condensates past a polarized obstacle that attracts one component of the condensate and repels the other one. The breather exists if intraspecies interaction constants differ from the interspecies interaction constant, and it corresponds to the nonlinear excitation of the so-called polarization mode with domination of the relative motion of the components. Analytical theory is developed for the case of small-amplitude breathers that is in reasonable agreement with the numerical results.
Lobanov, Valery E; Kartashov, Yaroslav V; Konotop, Vladimir V
2014-05-01
Using the parity and time reversal symmetries of a two-dimensional spin-orbit coupled Bose-Einstein condensate in a lattice created by the Zeeman field, we identify and find numerically various families of localized solutions, including multipole and half-vortex solitons. The obtained solutions may exist at any direction of the gauge field with respect to the lattice and can be found either in finite gaps (for repulsive interatomic interactions) or in a semi-infinite gap (for attractive interactions). The existence of half-vortices requires higher symmetry (the reflection with respect to the field direction). Stability of these modes makes them feasible for experimental observation.
Ning Boyuan; Zhuang Jun; Zhang Wenxian; You, J. Q.
2011-07-15
We study the enhancement of spin coherence with periodic, concatenated, or Uhrig dynamical decoupling N-pulse sequences in a spin-1 Bose-Einstein condensate, where the intrinsic dynamical instability in such a ferromagnetically interacting condensate causes spin decoherence and eventually leads to a multiple spatial-domain structure or a spin texture. Our results show that all three sequences successfully enhance the spin coherence by pushing the wave vector of the most unstable mode in the condensate to a larger value. Among the three sequences with the same number of pulses, the concatenated one shows the best performance in preserving the spin coherence. More interestingly, we find that all three sequences exactly follow the same enhancement law, k{sub -}T{sup 1/2}=c, with k{sub -} the wave vector of the most unstable mode, T the sequence period, and c a sequence-dependent constant. Such a law between k{sub -} and T is also derived analytically for an attractive scalar Bose-Einstein condensate subjected to a periodic dynamical decoupling sequence.
Engineering bright solitons to enhance the stability of two-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Radha, R.; Vinayagam, P. S.; Sudharsan, J. B.; Liu, Wu-Ming; Malomed, Boris A.
2015-12-01
We consider a system of coupled Gross-Pitaevskii (GP) equations describing a binary quasi-one-dimensional Bose-Einstein condensate (BEC) with intrinsic time-dependent attractive interactions, placed in a time-dependent expulsive parabolic potential, in a special case when the system is integrable (a deformed Manakov's system). Since the nonlinearity in the integrable system which represents binary attractive interactions exponentially decays with time, solitons are also subject to decay. Nevertheless, it is shown that the robustness of bright solitons can be enhanced in this system, making their respective lifetime longer, by matching the time dependence of the interaction strength (adjusted with the help of the Feshbach-resonance management) to the time modulation of the strength of the parabolic potential. The analytical results, and their stability, are corroborated by numerical simulations. In particular, we demonstrate that the addition of random noise does not impact the stability of the solitons.
Bright solitons in a two-dimensional spin-orbit-coupled dipolar Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Xu, Yong; Zhang, Yongping; Zhang, Chuanwei
2015-07-01
We study a two-dimensional spin-orbit-coupled dipolar Bose-Einstein condensate with repulsive contact interactions by both the variational method and the imaginary-time evolution of the Gross-Pitaevskii equation. The dipoles are completely polarized along one direction in the two-dimensional plane to provide an effective attractive dipole-dipole interaction. We find two types of solitons as the ground states arising from such attractive dipole-dipole interactions: a plane-wave soliton with a spatially varying phase and a stripe soliton with a spatially oscillating density for each component. Both types of solitons possess smaller size and higher anisotropy than the soliton without spin-orbit coupling. Finally, we discuss the properties of moving solitons, which are nontrivial because of the violation of Galilean invariance.
Bose-Einstein condensation of erbium.
Aikawa, K; Frisch, A; Mark, M; Baier, S; Rietzler, A; Grimm, R; Ferlaino, F
2012-05-25
We report on the achievement of Bose-Einstein condensation of erbium atoms and on the observation of magnetic Feshbach resonances at low magnetic fields. By means of evaporative cooling in an optical dipole trap, we produce pure condensates of 168Er, containing up to 7×10(4) atoms. Feshbach spectroscopy reveals an extraordinary rich loss spectrum with six loss resonances already in a narrow magnetic-field range up to 3 G. Finally, we demonstrate the application of a low-field Feshbach resonance to produce a tunable dipolar Bose-Einstein condensate and we observe its characteristic d-wave collapse. PMID:23003221
Bose-Einstein condensation. Twenty years after
Bagnato, V. S.; Frantzeskakis, D. J.; Kevrekidis, P. G.; Malomed, B. A.; Mihalache, D.
2015-02-23
The aim of this introductory article is two-fold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.
Levitating soliton of the Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Vysotina, N. V.; Rosanov, N. N.
2016-07-01
We have proposed a mechanical model that corresponds to the Newton equation for describing the dynamics of an oscillon, viz., a soliton-like cluster of the Bose-Einstein condensate (with atomic attraction) placed above an oscillating atomic mirror in a uniform gravitational field. The model describes the stochastic Fermi acceleration and periodic, quasi-periodic, and chaotic motion of the oscillon center, as well as hysteresis phenomena in the case of a slow variation of mirror oscillation frequency, which are in good agreement with the results obtained using the Gross-Pitaevskii equation.
Crystallized and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates.
Liu, Chao-Fei; Fan, Heng; Gou, Shih-Chuan; Liu, Wu-Ming
2014-02-27
Vortex is a topological defect with a quantized winding number of the phase in superfluids and superconductors. Here, we investigate the crystallized (triangular, square, honeycomb) and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates (BECs) by using the damped projected Gross-Pitaevskii equation. The amorphous vortices are the result of the considerable deviation induced by the interaction of atomic-molecular vortices. By changing the atom-molecule interaction from attractive to repulsive, the configuration of vortices can change from an overlapped atomic-molecular vortices to carbon-dioxide-type ones, then to atomic vortices with interstitial molecular vortices, and finally into independent separated ones. The Raman detuning can tune the ratio of the atomic vortex to the molecular vortex. We provide a phase diagram of vortices in rotating atomic-molecular BECs as a function of Raman detuning and the strength of atom-molecule interaction.
Crystallized and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates
Liu, Chao-Fei; Fan, Heng; Gou, Shih-Chuan; Liu, Wu-Ming
2014-01-01
Vortex is a topological defect with a quantized winding number of the phase in superfluids and superconductors. Here, we investigate the crystallized (triangular, square, honeycomb) and amorphous vortices in rotating atomic-molecular Bose-Einstein condensates (BECs) by using the damped projected Gross-Pitaevskii equation. The amorphous vortices are the result of the considerable deviation induced by the interaction of atomic-molecular vortices. By changing the atom-molecule interaction from attractive to repulsive, the configuration of vortices can change from an overlapped atomic-molecular vortices to carbon-dioxide-type ones, then to atomic vortices with interstitial molecular vortices, and finally into independent separated ones. The Raman detuning can tune the ratio of the atomic vortex to the molecular vortex. We provide a phase diagram of vortices in rotating atomic-molecular BECs as a function of Raman detuning and the strength of atom-molecule interaction. PMID:24573303
Number-conserving master equation theory for a dilute Bose-Einstein condensate
Schelle, Alexej; Wellens, Thomas; Buchleitner, Andreas; Delande, Dominique
2011-01-15
We describe the transition of N weakly interacting atoms into a Bose-Einstein condensate within a number-conserving quantum master equation theory. Based on the separation of time scales for condensate formation and noncondensate thermalization, we derive a master equation for the condensate subsystem in the presence of the noncondensate environment under the inclusion of all two-body interaction processes. We numerically monitor the condensate particle number distribution during condensate formation, and derive a condition under which the unique equilibrium steady state of a dilute, weakly interacting Bose-Einstein condensate is given by a Gibbs-Boltzmann thermal state of N noninteracting atoms.
Quantum metrology with Bose-Einstein condensates
Boixo, Sergio; Datta, Animesh; Davis, Matthew J.; Flammia, Steven T.; Shaji, Anil; Tacla, Alexandre B.; Caves, Carlton M.
2009-04-13
We show how a generalized quantum metrology protocol can be implemented in a two-mode Bose-Einstein condensate of n atoms, achieving a sensitivity that scales better than 1/n and approaches 1/n{sup 3/2} for appropriate design of the condensate.
Nonlinear localized modes in dipolar Bose-Einstein condensates in two-dimensional optical lattices
NASA Astrophysics Data System (ADS)
Rojas-Rojas, Santiago; Naether, Uta; Delgado, Aldo; Vicencio, Rodrigo A.
2016-09-01
We analyze the existence and properties of discrete localized excitations in a Bose-Einstein condensate loaded into a periodic two-dimensional optical lattice, when a dipolar interaction between atoms is present. The dependence of the Number of Atoms (Norm) on the energy of solutions is studied, along with their stability. Two important features of the system are shown, namely, the absence of the Norm threshold required for localized solutions to exist in finite 2D systems, and the existence of regions in the parameter space where two fundamental solutions are simultaneously unstable. This feature enables mobility of localized solutions, which is an uncommon feature in 2D discrete nonlinear systems. With attractive dipolar interaction, a non-trivial behavior of the Norm dependence is obtained, which is well described by an analytical model.
Impurity in a Bose-Einstein Condensate and the Efimov Effect
NASA Astrophysics Data System (ADS)
Levinsen, Jesper; Parish, Meera M.; Bruun, Georg M.
2015-09-01
We investigate the zero-temperature properties of an impurity particle interacting with a Bose-Einstein condensate (BEC), using a variational wave function that includes up to two Bogoliubov excitations of the BEC. This allows one to capture three-body Efimov physics, as well as to recover the first nontrivial terms in the weak-coupling expansion. We show that the energy and quasiparticle residue of the dressed impurity (polaron) are significantly lowered by three-body correlations, even for weak interactions where there is no Efimov trimer state in a vacuum. For increasing attraction between the impurity and the BEC, we observe a smooth crossover from atom to Efimov trimer, with a superposition of states near the Efimov resonance. We furthermore demonstrate that three-body loss does not prohibit the experimental observation of these effects. Our results thus suggest a route to realizing Efimov physics in a stable quantum many-body system for the first time.
Occupation Statistics of a Bose-Einstein Condensate for a Driven Landau-Zener Crossing
Smith-Mannschott, Katrina; Chuchem, Maya; Cohen, Doron; Hiller, Moritz; Kottos, Tsampikos
2009-06-12
We consider an atomic Bose-Einstein condensate loaded in a biased double-well trap with tunneling rate K and interatomic interaction U. The Bose-Einstein condensate is prepared such that all N atoms are in the left well. We drive the system by sweeping the potential difference E between the two wells. Depending on the interaction u=NU/K and the sweep rate E, we distinguish three dynamical regimes: adiabatic, diabatic, and sudden and consider the occupation statistics of the final state. The analysis goes beyond mean-field theory and is complemented by a semiclassical picture.
Nonlinear beam splitter in Bose-Einstein-condensate interferometers
Pezze, L.; Smerzi, A.; Berman, G. P.; Bishop, A. R.; Collins, L. A.
2006-09-15
A beam splitter is an important component of an atomic/optical Mach-Zehnder interferometer. Here we study a Bose-Einstein condensate beam splitter, realized with a double well potential of tunable height. We analyze how the sensitivity of a Mach-Zehnder interferometer is degraded by the nonlinear particle-particle interaction during the splitting dynamics. We distinguish three regimes, Rabi, Josephson and Fock, and associate to them a different scaling of the phase sensitivity with the total number of particles.
Entanglement generation in quantum networks of Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Pyrkov, Alexey N.; Byrnes, Tim
2013-09-01
Two component (spinor) Bose-Einstein condensates (BECs) are considered as the nodes of an interconnected quantum network. Unlike standard single-system qubits, in a BEC the quantum information is duplicated in a large number of identical bosonic particles, thus can be considered to be a ‘macroscopic’ qubit. One of the difficulties with such a system is how to effectively interact such qubits together in order to transfer quantum information and create entanglement. Here we propose a scheme of cavities containing spinor BECs coupled by optical fiber in order to achieve this task. We discuss entanglement generation and quantum state transfer between nodes using such macroscopic BEC qubits.
Stability of self-gravitating Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Schroven, Kris; List, Meike; Lämmerzahl, Claus
2015-12-01
We study the ground state and the first three radially excited states of a self-gravitating Bose-Einstein condensate with respect to the influence of two external parameters, the total mass and the strength of interactions between particles. For this we use the so-called Gross-Pitaevskii-Newton system. In this context we especially determine the case of very high total masses where the ground state solutions of the Gross-Pitaevskii-Newton system can be approximated with the Thomas-Fermi limit. Furthermore, stability properties of the computed radially excited states are examined by applying arguments of the catastrophe theory.
Bose-Einstein condensation in binary mixture of Bose gases
Tran Huu Phat; Le Viet Hoa; Nguyen Tuan Anh Nguyen Van Long
2009-10-15
The Bose-Einstein condensation (BEC) in a binary mixture of Bose gases is studied by means of the Cornwall-Jackiw-Tomboulis (CJT) effective action approach. The equations of state (EoS) and various scenarios of phase transitions of the system are considered in detail, in particular, the numerical computations are carried out for symmetry restoration (SR), symmetry nonrestoration (SNR) and inverse symmetry breaking (ISB) for getting an insight into their physical nature. It is shown that due to the cross interaction between distinct components of mixture there occur two interesting phenomena: the high temperature BEC and the inverse BEC, which could be tested in experiments.
Collapse dynamics of a {sup 176}Yb-{sup 174}Yb Bose-Einstein condensate
Chaudhary, G. K.; Ramakumar, R.
2010-06-15
In this paper, we present a theoretical study of a two-component Bose-Einstein condensate composed of ytterbium (Yb) isotopes in a three-dimensional anisotropic harmonic potential. The condensate consists of a mixture of {sup 176}Yb atoms which have a negative s-wave scattering length and {sup 174}Yb atoms having a positive s-wave scattering length. We study the ground-state as well as dynamic properties of this two-component condensate. Due to the attractive interactions between {sup 176}Yb atoms, the condensate of {sup 176}Yb undergoes a collapse when the particle number exceeds a critical value. The critical number and the collapse dynamics are modified due to the presence of {sup 174}Yb atoms. We use coupled two-component Gross-Pitaevskii equations to study the collapse dynamics. The theoretical results obtained are in reasonable agreement with the experimental results of Fukuhara et al. [Phys. Rev. A 79, 021601(R) (2009)].
Pair-correlation function of a metastable helium Bose-Einstein condensate
Zin, Pawel; Trippenbach, Marek; Gajda, Mariusz
2004-02-01
The pair-correlation function is one of the basic quantities to characterize the coherence properties of a Bose-Einstein condensate. We calculate this function in the experimentally important case of a zero temperature Bose-Einstein condensate in a metastable triplet helium state using the variational method with a pair-excitation ansatz. We compare our result with a pair-correlation function obtained for the hard-sphere potential with the same scattering length. Both functions are practically indistinguishable for distances greater than the scattering length. At smaller distances, due to interatomic interactions, the helium condensate shows strong correlations.
Dynamic properties of dilute Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Durfee, Dallin S.
In this thesis, a new apparatus for the study of Bose- Einstein condensation is described, and the first two experiments performed with the new device are discussed. The new instrument was constructed for the creation of dilute gas sodium Bose-Einstein condensates, and features an optical quality quartz cell, a high-flux spin-flip Zeeman slower, a tightly confining magnetic trap, and a high-resolution imaging system. The theory, design, and construction of each component is discussed, including a detailed explanation of non-destructive dispersive imaging. Bose-Einstein condensation was first achieved in the new apparatus in January of this year. Bose condensates consisting of 10 to 25 million atoms can be produced in this apparatus at a rate of two condensates per minute. The first two experiments performed with the new instrument probed the dynamic properties of dilute Bose condensates, allowing comparisons to be made with long standing theories of weakly-interacting degenerate Bose fluids. The first experiment was the study of ``surface wave'' excitations of Bose condensates. Standing and rotating quadrupole and octopole excitations were driven with a novel scanned optical dipole potential, a new tool which allows us to generate arbitrary two-dimensional perturbations to the trapping potential which confines the atoms. The second experiment studied the transition from dissipationless to dissipative flow in a Bose condensate. This study, performed by ``stirring'' the condensate with a focused laser, provided the first experimental evidence for the existence of a critical velocity for dissipation in dilute gas Bose condensates. This experiment is discussed in the context of earlier studies of the critical velocity of superfluid liquid helium. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)
Vortex structures of a two-component Bose-Einstein condensate for large anisotropies
Wei Ran; Mueller, Erich
2011-12-15
We calculate the vortex structures of an elongated two-component Bose-Einstein condensate. We study how these structures depend on the intracomponent and intercomponent interaction strengths. We present analytical and numerical results respectively at weak and strong interactions; finding lattices with different interlocking geometries: triangular, square, rectangular, and double core.
Bose-Einstein condensation in microgravity.
van Zoest, T; Gaaloul, N; Singh, Y; Ahlers, H; Herr, W; Seidel, S T; Ertmer, W; Rasel, E; Eckart, M; Kajari, E; Arnold, S; Nandi, G; Schleich, W P; Walser, R; Vogel, A; Sengstock, K; Bongs, K; Lewoczko-Adamczyk, W; Schiemangk, M; Schuldt, T; Peters, A; Könemann, T; Müntinga, H; Lämmerzahl, C; Dittus, H; Steinmetz, T; Hänsch, T W; Reichel, J
2010-06-18
Albert Einstein's insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.
Astrophysical Bose-Einstein condensates and superradiance
NASA Astrophysics Data System (ADS)
Kühnel, Florian; Rampf, Cornelius
2014-11-01
We investigate gravitational analogue models to describe slowly rotating objects (e.g., dark-matter halos, or boson stars) in terms of Bose-Einstein condensates, trapped in their own gravitational potentials. We begin with a modified Gross-Pitaevskii equation, and show that the resulting background equations of motion are stable, as long as the rotational component is treated as a small perturbation. The dynamics of the fluctuations of the velocity potential are effectively governed by the Klein-Gordon equation of an "Eulerian metric," where we derive the latter by the use of a relativistic Lagrangian extrapolation. Superradiant scattering on such objects is studied. We derive conditions for its occurrence and estimate its strength. Our investigations might give an observational handle to phenomenologically constrain Bose-Einstein condensates.
Bose-Einstein Condensation in Microgravity
NASA Astrophysics Data System (ADS)
van Zoest, T.; Gaaloul, N.; Singh, Y.; Ahlers, H.; Herr, W.; Seidel, S. T.; Ertmer, W.; Rasel, E.; Eckart, M.; Kajari, E.; Arnold, S.; Nandi, G.; Schleich, W. P.; Walser, R.; Vogel, A.; Sengstock, K.; Bongs, K.; Lewoczko-Adamczyk, W.; Schiemangk, M.; Schuldt, T.; Peters, A.; Könemann, T.; Müntinga, H.; Lämmerzahl, C.; Dittus, H.; Steinmetz, T.; Hänsch, T. W.; Reichel, J.
2010-06-01
Albert Einstein’s insight that it is impossible to distinguish a local experiment in a “freely falling elevator” from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.
Bose-Einstein condensation in microgravity.
van Zoest, T; Gaaloul, N; Singh, Y; Ahlers, H; Herr, W; Seidel, S T; Ertmer, W; Rasel, E; Eckart, M; Kajari, E; Arnold, S; Nandi, G; Schleich, W P; Walser, R; Vogel, A; Sengstock, K; Bongs, K; Lewoczko-Adamczyk, W; Schiemangk, M; Schuldt, T; Peters, A; Könemann, T; Müntinga, H; Lämmerzahl, C; Dittus, H; Steinmetz, T; Hänsch, T W; Reichel, J
2010-06-18
Albert Einstein's insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter. PMID:20558713
Schrodinger Leopards in Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Carr, Lincoln D.; Dounas-Frazer, Dimitri R.
2008-03-01
We present the complex quantum dynamics of vortices in Bose-Einstein condensates in a double well via exact diagonalization of a discretized Hamiltonian. When the barrier is high, vortices evolve into macroscopic superposition (NOON) states of a vortex in either well -- a Schrodinger cat with spots. Such Schrodinger leopard states are more robust than previously proposed NOON states, which only use two single particle modes of the double well potential.
Bose-Einstein correlations from 'within'
Utyuzh, O. V.; Wilk, G.; Wlodarczyk, Z.
2006-04-11
We describe an attempt to model numerically Bose-Einstein correlations (BEC) from 'within', i.e., by using them as the most fundamental ingredient of some Monte Carlo event generator (MC) rather than considering them as a kind of (more or less important, depending on the actual situation) 'afterburner', which inevitably changes original physical content of the MC code used to model multiparticle production process.
Mechanocaloric and thermomechanical effects in Bose-Einstein-condensed systems
Marques, G.C.; Bagnato, V.S.; Muniz, S.R.; Spehler, D.
2004-05-01
In this paper we extend previous hydrodynamic equations, governing the motion of Bose-Einstein-condensed fluids, to include temperature effects. This allows us to analyze some differences between a normal fluid and a Bose-Einstein-condensed one. We show that, in close analogy with superfluid {sup 4}He, a Bose-Einstein-condensed fluid exhibits the mechanocaloric and thermomechanical effects. In our approach we can explain both effects without using the hypothesis that the Bose-Einstein-condensed fluid has zero entropy. Such ideas could be investigated in existing experiments.
Localization of two-component Bose-Einstein condensates in optical lattices.
Ostrovskaya, Elena A; Kivshar, Yuri S
2004-05-01
We study nonlinear localization of a two-component Bose-Einstein condensate (BEC) in a one-dimensional optical lattice. Our theory shows that spin-dependent optical lattices can be used to effectively manipulate the nonlinear interactions between the BEC components, and to observe composite localized states of a BEC in both bands and gaps of the matter-wave spectrum.
Integrated Mach-Zehnder interferometer for Bose-Einstein condensates.
Berrada, T; van Frank, S; Bücker, R; Schumm, T; Schaff, J-F; Schmiedmayer, J
2013-01-01
Particle-wave duality enables the construction of interferometers for matter waves, which complement optical interferometers in precision measurement devices. This requires the development of atom-optics analogues to beam splitters, phase shifters and recombiners. Integrating these elements into a single device has been a long-standing goal. Here we demonstrate a full Mach-Zehnder sequence with trapped Bose-Einstein condensates confined on an atom chip. Particle interactions in our Bose-Einstein condensate matter waves lead to a nonlinearity, absent in photon optics. We exploit it to generate a non-classical state having reduced number fluctuations inside the interferometer. Making use of spatially separated wave packets, a controlled phase shift is applied and read out by a non-adiabatic matter-wave recombiner. We demonstrate coherence times a factor of three beyond what is expected for coherent states, highlighting the potential of entanglement as a resource for metrology. Our results pave the way for integrated quantum-enhanced matter-wave sensors. PMID:23804159
Particle Correlations in Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Jiang, Zhang
The impact of interparticle correlations on the behavior of Bose-Einstein Condensates (BECs) is discussed using two approaches. In the first approach, the wavefunction of a BEC is encoded in the N-particle sector of an extended "catalytic state". Going to a time-dependent interaction picture, we can organize the effective Hamiltonian by powers of N -1/2 . Requiring the terms of order N 1/2 to vanish, we get the Gross-Pitaevskii Equation. Going to the next order, N0, we obtain the number-conserving Bogoliubov approximation. Our approach allows one to stay in the Schrodinger picture and to apply many techniques from quantum optics. Moreover, it is easier to track different orders in the Hamiltonian and to generalize to the multi-component case. In the second approach, I consider a state of N = l x n bosons that is derived by symmetrizing the n-fold tensor product of an arbitrary l-boson state. Particularly, we are interested in the pure state case for l = 2, which we call the Pair-Correlated State (PCS). I show that PCS reproduces the number-conserving Bogoliubov approximation; moreover, it also works in the strong interaction regime where the Bogoliubov approximation fails. For the two-site Bose-Hubbard model, I find numerically that the error (measured by trace distance of the two-particle RDMs) of PCS is less than two percent over the entire parameter space, thus making PCS a bridge between the super uid and Mott insulating phases. Amazingly, the error of PCS does not increase, in the time-dependent case, as the system evolves for longer times. I derive both time-dependent and -independent equations for the ground state and the time evolution of the PCS ansatz. The time complexity of simulating PCS does not depend on N and is linear in the number of orbitals in use. Compared to other methods, e.g, the Jastrow wavefunction, the Gutzwiller wavefunction, and the multi-configurational time-dependent Hartree method, our approach does not require quantum Monte Carlo nor
Knot Solitons in Spinor Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Hall, David; Ray, Michael; Tiurev, Konstantin; Ruokokoski, Emmi; Gheorghe, Andrei Horia; Möttönen, Mikko
2016-05-01
Knots are familiar entities that appear at a captivating nexus of art, technology, mathematics and science. Following a lengthy period of theoretical investigation and development, they have recently attracted great experimental interest in classical contexts ranging from knotted DNA and nanostructures to vortex knots in fluids. We demonstrate here the controlled creation and detection of knot solitons in the quantum-mechanical order parameter of a spinor Bose-Einstein condensate. Images of the superfluid reveal the circular shape of the soliton core and its associated linked rings. Our observations of the knot soliton establish an experimental foundation for future studies of their stability, dynamics and applications within quantum systems. Supported in part by NSF Grant PHY-1205822.
Photon condensation: A new paradigm for Bose-Einstein condensation
NASA Astrophysics Data System (ADS)
Rajan, Renju; Ramesh Babu, P.; Senthilnathan, K.
2016-10-01
Bose-Einstein condensation is a state of matter known to be responsible for peculiar properties exhibited by superfluid Helium-4 and superconductors. Bose-Einstein condensate (BEC) in its pure form is realizable with alkali atoms under ultra-cold temperatures. In this paper, we review the experimental scheme that demonstrates the atomic Bose-Einstein condensate. We also elaborate on the theoretical framework for atomic Bose-Einstein condensation, which includes statistical mechanics and the Gross-Pitaevskii equation. As an extension, we discuss Bose-Einstein condensation of photons realized in a fluorescent dye filled optical microcavity. We analyze this phenomenon based on the generalized Planck's law in statistical mechanics. Further, a comparison is made between photon condensate and laser. We describe how photon condensate may be a possible alternative for lasers since it does not require an energy consuming population inversion process.
NASA Astrophysics Data System (ADS)
Galteland, Peder Notto; Babaev, Egor; Sudbø, Asle
2015-01-01
Thermal fluctuations and melting transitions for rotating single-component superfluids have been intensively studied and are well understood. In contrast, the thermal effects on vortex states for two-component superfluids with density-density interaction, which have a much richer variety of vortex ground states, have been much less studied. Here, we investigate the thermal effects on vortex matter in superfluids with U (1 )×U (1 ) broken symmetries and intercomponent density-density interactions, as well as the case with a larger SU (2 ) broken symmetry obtainable from the [U (1 )×U (1 )] -symmetric case by tuning scattering lengths. In the former case we find that, in addition to first-order melting transitions, the system exhibits thermally driven phase transitions between square and hexagonal lattices. Our main result, however, concerns the case where the condensate exhibits SU (2 ) symmetry, and where vortices are not topological. At finite temperature, the system exhibits effects which do not have a counterpart in single-component systems. Namely, it has a state where thermally averaged quantities show no regular vortex lattice, yet the system retains superfluid coherence along the axis of rotation. In such a state, the thermal fluctuations result in transitions between different (nearly) degenerate vortex states without undergoing a melting transition. Our results apply to multicomponent Bose-Einstein condensates, and we suggest how to detect some of these unusual effects experimentally in such systems.
Bose-Einstein Condensation in Extended Microgravity
NASA Astrophysics Data System (ADS)
Scharringhausen, Marco; Quantus Team; Rasel, Ernst Maria
2012-07-01
The setup and the envisaged experiment timeline of the QUANTUS-III experiment onboard a sounding rocket to be started in the near future are presented. The major intention of QUANTUS-III is the stable generation of a number of Bose-Einstein condensates as a source for atom interferometry during several minutes of microgravity onboard the sounding rocket. Later missions aim at the realization of atom interferoemeters as precursor satellite missions. These condesates will be generated serially, allowing a large number of repeatable tests. Within such Bose-Einstein condensates, millions of atoms lose their identity and can be described by a single macroscopic wave function. During the expansion over several seconds, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter. Cold quantum gases and, in particular, Bose-Einstein condensates represent a new state of matter which is nowadays established in many laboratories. They offer unique insights into a broad range of fundamental physics as well as prospects for novel quantum sensors. Microgravity will substantially extend the science of quantum gases towards nowadays inaccessible regimes at lowest temperatures, to macroscopic dimensions, and to unequalled durations of unperturbed evolution of these distinguished quantum objects. Right now, the QUANTUS-III experiment is in the development phase, taking heritage from QUANTUS-I and QUANTUS-II. Major components of the engineering model are available. Boundary conditions of the rocket, requirements of the experiment and interface considerations are presented. This include laser stabilization, vacuum technology and magnetic shielding. The planned trajectory of the rocket will have an apogee of 200 - 300 km and a total microgravity time of 4 - 7 minutes, both depending on the total experiment mass.
Internal Josephson effects in spinor dipolar Bose-Einstein condensates
Yasunaga, Masashi; Tsubota, Makoto
2010-02-15
We theoretically study the internal Josephson effect, which is driven by spin-exchange interactions and magnetic dipole-dipole interactions, in a three-level system for spin-1 Bose-Einstein condensates, obtaining novel spin dynamics. We introduce single spatial mode approximations into the Gross-Pitaevskii equations and derive the Josephson-type equations, which are analogous to tunneling currents through three junctions between three superconductors. From an analogy with two interacting nonrigid pendulums, we identify unique varied oscillational modes, called the 0-{pi}, 0-running, running-running, 2n{pi} and running-2{pi}, single nonrigid pendulum, and two rigid pendulums phase modes. These Josephson modes in the three states are expected to be found in real atomic Bose gas systems.
Dissipative transport of a Bose-Einstein condensate
Dries, D.; Pollack, S. E.; Hitchcock, J. M.; Hulet, R. G.
2010-09-15
We investigate the effects of impurities, either correlated disorder or a single Gaussian defect, on the collective dipole motion of a Bose-Einstein condensate of {sup 7}Li in an optical trap. We find that this motion is damped at a rate dependent on the impurity strength, condensate center-of-mass velocity, and interatomic interactions. Damping in the Thomas-Fermi regime depends universally on the disordered potential strength scaled to the condensate chemical potential and the condensate velocity scaled to the speed of sound. The damping rate is comparatively small in the weakly interacting regime, and, in this case, is accompanied by strong condensate fragmentation. In situ and time-of-flight images of the atomic cloud provide evidence that this fragmentation is driven by dark soliton formation.
Spin-Orbit Coupled Spinor Bose-Einstein Condensates
Wang Chunji; Gao Chao; Jian Chaoming; Zhai Hui
2010-10-15
An effective spin-orbit coupling can be generated in a cold atom system by engineering atom-light interactions. In this Letter we study spin-1/2 and spin-1 Bose-Einstein condensates with Rashba spin-orbit coupling, and find that the condensate wave function will develop nontrivial structures. From numerical simulation we have identified two different phases. In one phase the ground state is a single plane wave, and often we find the system splits into domains and an array of vortices plays the role of a domain wall. In this phase, time-reversal symmetry is broken. In the other phase the condensate wave function is a standing wave, and it forms a spin stripe. The transition between them is driven by interactions between bosons. We also provide an analytical understanding of these results and determine the transition point between the two phases.
Spin-orbit coupled spinor Bose-Einstein condensates.
Wang, Chunji; Gao, Chao; Jian, Chao-Ming; Zhai, Hui
2010-10-15
An effective spin-orbit coupling can be generated in a cold atom system by engineering atom-light interactions. In this Letter we study spin-1/2 and spin-1 Bose-Einstein condensates with Rashba spin-orbit coupling, and find that the condensate wave function will develop nontrivial structures. From numerical simulation we have identified two different phases. In one phase the ground state is a single plane wave, and often we find the system splits into domains and an array of vortices plays the role of a domain wall. In this phase, time-reversal symmetry is broken. In the other phase the condensate wave function is a standing wave, and it forms a spin stripe. The transition between them is driven by interactions between bosons. We also provide an analytical understanding of these results and determine the transition point between the two phases.
Quantum filaments in dipolar Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Wächtler, F.; Santos, L.
2016-06-01
Collapse in dipolar Bose-Einstein condensates may be arrested by quantum fluctuations. Due to the anisotropy of the dipole-dipole interactions, the dipole-driven collapse induced by soft excitations is compensated by the repulsive Lee-Huang-Yang contribution resulting from quantum fluctuations of hard excitations, in a similar mechanism as that recently proposed for Bose-Bose mixtures. The arrested collapse results in self-bound filamentlike droplets, providing an explanation for the intriguing results of recent dysprosium experiments. Arrested instability and droplet formation are general features directly linked to the nature of the dipole-dipole interactions, and should hence play an important role in all future experiments with strongly dipolar gases.
Matter-waves in Bose-Einstein condensates with spin-orbit and Rabi couplings
NASA Astrophysics Data System (ADS)
Chiquillo, Emerson
2015-11-01
We investigate the one-dimensional (1D) and two-dimensional (2D) reduction of a quantum field theory starting from the three-dimensional (3D) many-body Hamiltonian of interacting bosons with spin-orbit (SO) and Rabi couplings. We obtain the effective time-dependent 1D and 2D nonpolynomial Heisenberg equations for both the repulsive and attractive signs of the inter-atomic interaction. Our findings show that in the case in which the many-body state coincides with the Glauber coherent state, the 1D and 2D Heisenberg equations become 1D and 2D nonpolynomial Schrödinger equations (NPSEs). These models were derived in a mean-field approximation from 3D Gross-Pitaevskii equation (GPE), describing a Bose-Einstein condensate (BEC) with SO and Rabi couplings. In the present work self-repulsive and self-attractive localized solutions of the 1D NPSE and the 1D GPE are obtained in a numerical form. The combined action of SO and Rabi couplings produces conspicuous sidelobes on the density profile, for both signs of the interaction. In the case of the attractive nonlinearity, an essential result is the possibility of getting an unstable condensate by the increasing of SO coupling.
Dynamics of nonautonomous rogue waves in Bose-Einstein condensate
Zhao, Li-Chen
2013-02-15
We study rogue waves of Bose-Einstein condensate (BEC) analytically in a time-dependent harmonic trap with a complex potential. Properties of the nonautonomous rogue waves are investigated analytically. It is reported that there are possibilities to 'catch' rogue waves through manipulating nonlinear interaction properly. The results provide many possibilities to manipulate rogue waves experimentally in a BEC system. - Highlights: Black-Right-Pointing-Pointer One more generalized rogue wave solutions are presented. Black-Right-Pointing-Pointer Present one possible way to catch a rouge wave. Black-Right-Pointing-Pointer Properties of rogue waves are investigated analytically for the first time. Black-Right-Pointing-Pointer Provide many possibilities to manipulate rogue waves in BEC.
Emergence of classical rotation in superfluid Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
White, Angela; Hennessy, Tara; Busch, Thomas
2016-03-01
Phase transitions can modify quantum behavior on mesoscopic scales and give access to new and unusual quantum dynamics. Here we investigate the superfluid properties of a rotating two-component Bose-Einstein condensate as a function of changes in the interaction energy and in particular through the phase transition from miscibility to immiscibility. We show that the breaking of one of the hallmarks of superfluid flow, namely, the quantization condition on circulation, is continuous throughout an azimuthal phase-separation process and displays intriguing flow dynamics. We find that the resulting currents are stable for long times and possess a boundary between the two condensate components that exhibits classical solid-body rotation, despite the quantum nature of superfluid flow. To support this coexistence of classical and quantum behavior the system develops a unique velocity flow profile, which includes unusual radial flow in regions near the boundary.
Two-component Bose-Einstein condensates in periodic potential.
Kostov, N A; Enol'skii, V Z; Gerdjikov, V S; Konotop, V V; Salerno, M
2004-11-01
Coupled nonlinear Schrödinger (CNLS) equations with an external elliptic function potential model with high accuracy a quasi-one-dimensional interacting two-component Bose-Einstein condensate (BEC) trapped in a standing wave generated by a few laser beams. The construction of stationary solutions of the two-component CNLS equation with a periodic potential is detailed and their stability properties are studied by direct numerical simulations. Some of these solutions allow reduction to the Manakov system. From a physical point of view the trivial phase solutions can be interpreted as exact Bloch states at the edge of the Brillouin zone. Some of them are stable while others are found to be unstable against weak modulations of long wavelength. By numerical simulations it is shown that the modulationally unstable solutions lead to the formation of localized ground states of the coupled BEC system.
Spin-orbit coupled Bose-Einstein condensate under rotation.
Xu, Xiao-Qiang; Han, Jung Hoon
2011-11-11
We examine the combined effects of Rashba spin-orbit (SO) coupling and rotation on trapped spinor Bose-Einstein condensates. The nature of single particle states is thoroughly examined in the Landau level basis and is shown to support the formation of a half-quantum vortex. In the presence of weak s-wave interactions, the ground state at strong SO coupling develops ringlike structures with domains whose number shows step behavior with increasing rotation. For the fast rotation case, the vortex pattern favors a triangular lattice, accompanied by density depletion in the central region and a weakened Skyrmionic character as the SO coupling is enhanced. Giant vortex formation is facilitated when SO coupling and rotation are both strong.
Theoretical studies of Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Das, Kunal Kashyap
This thesis is a theoretical study of Bose-Einstein Condensation (BEC) in harmonically-trapped, weakly-interacting dilute gases. The motivation for this study is the experimental realization of BEC in trapped alkali gases since 1995. The weak inter-particle interactions and diluteness of the gases allow for a fairly accurate mean-field treatment and justifies a discrete quasi-particle description as we use in this work. This thesis considers three specific topics in the rapidly growing field of BEC theory: (i) interference effects in BEC, (ii) interaction-induced energy shifts and damping of excitations of condensates and (iii) the properties of highly anisotropic condensates. The results are summarized here: i. We show that if two multiply occupied boson modes are in eigenstates of the Hermitian relative phase operator, then the visibility of fringes formed by the interference between the modes is necessarily less than unity. For large total occupation numbers the visibility V ≤ pi/4. States with definite relative phase and unit visibility do exist. They are related to coherent states and are not orthogonal (not eigenstates of a Hermitian phase operator). This visibility limitation may make it possible to investigate experimentally the physical role of the relative phase eigenstates in interference measurements on BEC. ii. We evaluate analytically the asymptotic energy shifts of the high energy Bogoliubov quasi-particle modes. In spherical geometry, those modes display a 1/ n dependence on their number of radial nodes n but only a weak dependence on their angular momenta l. We obtain similar results for cylindrical geometry. We derive an implicit equation for the widths or decay rates gamma of the modes from an assumption of exponential decay. We use the equation to do a detailed numerical study of the trends in the behavior of the widths as a function of temperature, energy, particle number and scattering lengths. In particular, we find that widths due to
Vector azimuthons in two-component Bose-Einstein condensates
Lashkin, Volodymyr M.; Ostrovskaya, Elena A.; Desyatnikov, Anton S.; Kivshar, Yuri S.
2009-07-15
We introduce matter-wave vector azimuthons, i.e., spatially localized vortex states with azimuthal modulations of density, in multicomponent Bose-Einstein condensates. These localized states generalize spatially modulated vortex solitons introduced earlier in nonlinear optics [A. S. Desyatnikov, A. A. Sukhorukov, and Yu. S. Kivshar, Phys. Rev. Lett. 95, 203904 (2005)] and Bose-Einstein condensates [V. M. Lashkin, Phys. Rev. A 77, 025602 (2008)]. We find, numerically, nonrotating and rotating two-component azimuthons in a Bose-Einstein condensate with a negative scattering length confined by a quasi-two-dimensional parabolic trap.
Collapse of spin-orbit-coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Mardonov, Sh.; Sherman, E. Ya.; Muga, J. G.; Wang, Hong-Wei; Ban, Yue; Chen, Xi
2015-04-01
A finite-size quasi-two-dimensional Bose-Einstein condensate collapses if the attraction between atoms is sufficiently strong. Here we present a theory of collapse for condensates with the interatomic attraction and spin-orbit coupling. We consider two realizations of spin-orbit coupling: the axial Rashba coupling and the balanced, effectively one-dimensional Rashba-Dresselhaus one. In both cases spin-dependent "anomalous" velocity, proportional to the spin-orbit-coupling strength, plays a crucial role. For the Rashba coupling, this velocity forms a centrifugal component in the density flux opposite to that arising due to the attraction between particles and prevents the collapse at a sufficiently strong coupling. For the balanced Rashba-Dresselhaus coupling, the spin-dependent velocity can spatially split the initial state in one dimension and form spin-projected wave packets, reducing the total condensate density. Depending on the spin-orbit-coupling strength, interatomic attraction, and initial state, this splitting either prevents the collapse or modifies the collapse process. These results show that the collapse can be controlled by a spin-orbit coupling, thus extending the domain of existence of condensates of attracting atoms.
Enhanced stripe phases in spin-orbit-coupled Bose-Einstein condensates in ring cavities
NASA Astrophysics Data System (ADS)
Mivehvar, Farokh; Feder, David L.
2015-08-01
The coupled dynamics of the atom and photon fields in optical ring cavities with two counterpropagating modes give rise to both spin-orbit interactions as well as long-ranged interactions between atoms of a many-body system. At zero temperature, the interplay between the two-body and cavity-mediated interactions determines the ground state of a Bose-Einstein condensate. In this work, we find that cavity quantum electrodynamics in the weak-coupling regime favors a stripe-phase state over a plane-wave phase as the strength of cavity-mediated interactions increases. Indeed, the stripe phase is energetically stabilized even for condensates with attractive intraspecies and interspecies interactions for sufficiently large cavity interactions. The elementary excitation spectra in both phases correspond to linear dispersion relation at long wavelengths, indicating that both phases exhibit superfluidity, although the plane-wave phase also displays a characteristic roton-type feature. The results suggest that even in the weak-coupling regime, cavities can yield interesting new physics in ultracold quantum gases.
NASA Astrophysics Data System (ADS)
Cuesta, José A.; Sear, Richard P.
2002-03-01
Ideal bosons and a classical system of monomers that aggregate forming noninteracting ring polymers are known to have the same partition function. So, the ring polymers have a phase transition, the analogue of Bose-Einstein condensation of bosons. At this phase transition macroscopic polymers are formed. The link between these systems is made via Feynman's path integrals: these integrals are the same for the trajectories of the bosons in imaginary time and for the configurations of the polymers. We show that a transition of this general form occurs within a whole class of aggregating systems. Examples are the lamellae formation in suspensions of disclike micelles or the emulsification failure observed in water-oil-surfactant emulsions. As with bosons, the transition occurs even when aggregates do not interact. The λ-transition in 4He is believed to be Bose-Einstein condensation modified by interatomic interactions. We suggest that interaggregate interactions too only modify the transition we have found.
Conditions for Bose-Einstein condensation in magnetically trapped atomic cesium
NASA Astrophysics Data System (ADS)
Tiesinga, E.; Moerdijk, A. J.; Verhaar, B. J.; Stoof, H. T. C.
1992-08-01
We study conditions necessary for the observation of Bose-Einstein condensation in a magnetically trapped sample of atomic Cs gas. These conditions are associated with the value of the elastic scattering length, the rate of elastic scattering events, and the lifetime for decay of the density due to both magnetic dipole relaxation in two-body collisions, as well as recombination to Cs2 in three-body collisions. We find that, on the basis of these conditions, the prospects for observing Bose-Einstein condensation are favorable for a gas of ground-state Cs atoms in the highest state of the lowest hyperfine manifold. In all calculated elastic and inelastic two-body rates we find a pronounced resonance structure, which can be understood in terms of the interplay between the singlet-triplet interaction and the hyperfine, Zeeman, and magnetic dipole interactions. The experimental observation of these resonances may help to eliminate present uncertainties about interaction potentials.
Nonlinear interferometry with Bose-Einstein condensates
Tacla, Alexandre B.; Boixo, Sergio; Datta, Animesh; Shaji, Anil; Caves, Carlton M.
2010-11-15
We analyze a proposed experiment [Boixo et al., Phys. Rev. Lett. 101, 040403 (2008)] for achieving sensitivity scaling better than 1/N in a nonlinear Ramsey interferometer that uses a two-mode Bose-Einstein condensate (BEC) of N atoms. We present numerical simulations that confirm the analytical predictions for the effect of the spreading of the BEC ground-state wave function on the ideal 1/N{sup 3/2} scaling. Numerical integration of the coupled, time-dependent, two-mode Gross-Pitaevskii equations allows us to study the several simplifying assumptions made in the initial analytic study of the proposal and to explore when they can be justified. In particular, we find that the two modes share the same spatial wave function for a length of time that is sufficient to run the metrology scheme.
Bose-Einstein condensation of the classical axion field in cosmology?
Davidson, Sacha; Elmer, Martin E-mail: m.elmer@ipnl.in2p3.fr
2013-12-01
The axion is a motivated cold dark matter candidate, which it would be interesting to distinguish from weakly interacting massive particles. Sikivie has suggested that axions could behave differently during non-linear galaxy evolution, if they form a Bose-Einstein condensate, and argues that ''gravitational thermalisation'' drives them to a Bose-Einstein condensate during the radiation dominated era. Using classical equations of motion during linear structure formation, we explore whether the gravitational interactions of axions can generate enough entropy. At linear order in G{sub N}, we interpret that the principle activities of gravity are to expand the Universe and grow density fluctuations. To quantify the rate of entropy creation we use the anisotropic stress to estimate a short dissipation scale for axions which does not confirm previous estimates of their gravitational thermalisation rate.
Coherent zero-field magnetization resonance in a dipolar spin-1 Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Zhang, Wenxian; Yi, S.; Chapman, M. S.; You, J. Q.
2015-08-01
With current magnetic-field shielding and high-precision detection in dipolar spinor Bose-Einstein condensates, it is possible to experimentally detect the low- or zero-field nonsecular dipolar dynamics. Here we analytically investigate the zero-field nonsecular magnetic dipolar interaction effect, with an emphasis on magnetization dynamics in a spin-1 Bose-Einstein condensate under the single spatial mode approximation within the mean-field theory. Due to the biaxial nature of the dipolar interaction, a novel resonance occurs in the condensate magnetization oscillation, in contrast to the previous assumption of a conserved magnetization in strong magnetic fields. Furthermore, we propose a dynamical-decoupling detection method for such a resonance, which cancels the stray magnetic fields in experiment but restores the magnetization dynamics. Our results shed light on the dipolar systems and may find potential applications beyond cold atoms.
Nonequilibrium Bose-Einstein condensation of hot magnons
Vannucchi, Fabio Stucchi; Vasconcellos, Aurea Rosas; Luzzi, Roberto
2010-10-01
We present an analysis of the emergence of a nonequilibrium Bose-Einstein-type condensation of magnons in radio-frequency pumped magnetic thin films, which has recently been experimentally observed. A complete description of all the nonequilibrium processes involved is given. It is demonstrated that the phenomenon is another example of the emergence of Bose-Einstein-type condensation in nonequilibrium many-boson systems embedded in a thermal bath, a phenomenon evidenced decades ago by the renowned late Herbert Froehlich.
Soliton Creation During a Bose-Einstein Condensation
Damski, Bogdan; Zurek, Wojciech H.
2010-04-23
We use the stochastic Gross-Pitaevskii equation to study dynamics of Bose-Einstein condensation. We show that cooling into a Bose-Einstein condensate (BEC) can create solitons with density given by the cooling rate and by the critical exponents of the transition. Thus, counting solitons left in its wake should allow one to determine the critical exponents z and {nu} for a BEC phase transition. The same information can be extracted from two-point correlation functions.
Phase separation of two-component Bose-Einstein condensates
Liu, Zuhan
2009-10-15
Recently, coupled systems of nonlinear Schroedinger equations have been used extensively to describe mixtures Bose-Einstein condensates. In this paper, we study the distribution of two different hyperfine spin states of a binary mixture of three dimensional Bose-Einstein condensates. In a double condensate, an interface may occur due to large intraspecies and interspecies scattering lengths. We prove that there is an asymptotic separation of different phases in the strong coupling (Thomas-Fermi) limit.
Impurity in a Bose-Einstein condensate in a double well
Mulansky, F.; Mumford, J.; O'Dell, D. H. J.
2011-12-15
We compare and contrast the mean-field and many-body properties of a Bose-Einstein condensate trapped in a double-well potential with a single impurity atom. The mean-field solutions display a rich structure of bifurcations, as parameters such as the boson-impurity interaction strength and the tilt between the two wells are varied. In particular, we study a pitchfork bifurcation in the lowest mean-field stationary solution, which occurs when the boson-impurity interaction exceeds a critical magnitude. This bifurcation, which is present for both repulsive and attractive boson-impurity interactions, corresponds to the spontaneous formation of an imbalance in the number of particles between the two wells. If the boson-impurity interaction is large, the bifurcation is associated with the onset of a Schroedinger-cat state in the many-body ground state. We calculate the coherence and number fluctuations between the two wells, and also the entanglement entropy between the bosons and the impurity. We find that the coherence can be greatly enhanced at the bifurcation.
Ferrofluidity in a two-component dipolar Bose-Einstein condensate.
Saito, Hiroki; Kawaguchi, Yuki; Ueda, Masahito
2009-06-12
It is shown that the interface in a two-component Bose-Einstein condensate (BEC) with a dipole-dipole interaction spontaneously develops patterns similar to those formed in a ferrofluid. Hexagonal, labyrinthine, solitonlike structures, and hysteretic behavior are numerically demonstrated. Superflow is found to circulate around the hexagonal pattern at rest, offering evidence of supersolidity. The system sustains persistent current with a vortex line pinned by the hexagonal pattern. These phenomena may be realized using a 52Cr BEC.
Rotational response of two-component Bose-Einstein condensates in ring traps
Halkyard, P. L.; Jones, M. P. A.; Gardiner, S. A.
2010-06-15
We consider a two-component Bose-Einstein condensate in a ring trap in a rotating frame and show how to determine the response of such a configuration to being in a rotating frame via accumulation of a Sagnac phase. This may be accomplished through either population oscillations or the motion of spatial-density fringes. We explicitly include the effect of interactions via a mean-field description and study the fidelity of the dynamics relative to an ideal configuration.
Capillary instability in a two-component Bose-Einstein condensate
Sasaki, Kazuki; Suzuki, Naoya; Saito, Hiroki
2011-05-15
Capillary instability and the resulting dynamics in an immiscible two-component Bose-Einstein condensate are investigated using the mean-field and Bogoliubov analyses. A long, cylindrical condensate surrounded by the other component is dynamically unstable against breakup into droplets due to the interfacial tension arising from the quantum pressure and interactions. A heteronuclear system confined in a cigar-shaped trap is proposed for realizing this phenomenon experimentally.
Ferrofluidity in a Two-Component Dipolar Bose-Einstein Condensate
Saito, Hiroki; Kawaguchi, Yuki; Ueda, Masahito
2009-06-12
It is shown that the interface in a two-component Bose-Einstein condensate (BEC) with a dipole-dipole interaction spontaneously develops patterns similar to those formed in a ferrofluid. Hexagonal, labyrinthine, solitonlike structures, and hysteretic behavior are numerically demonstrated. Superflow is found to circulate around the hexagonal pattern at rest, offering evidence of supersolidity. The system sustains persistent current with a vortex line pinned by the hexagonal pattern. These phenomena may be realized using a {sup 52}Cr BEC.
Amplification of matter rogue waves and breathers in quasi-two-dimensional Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Manikandan, K.; Senthilvelan, M.; Kraenkel, R. A.
2016-02-01
We construct rogue wave and breather solutions of a quasi-two-dimensional Gross-Pitaevskii equation with a time-dependent interatomic interaction and external trap. We show that the trapping potential and an arbitrary functional parameter that present in the similarity transformation should satisfy a constraint for the considered equation to be integrable and yield the desired solutions. We consider two different forms of functional parameters and investigate how the density of the rogue wave and breather profiles vary with respect to these functional parameters. We also construct vector localized solutions of a two coupled quasi-two-dimensional Bose-Einstein condensate system. We then investigate how the vector localized density profiles modify in the constant density background with respect to the functional parameters. Our results may help to manipulate matter rogue waves experimentally in the two-dimensional Bose-Einstein condensate systems.
Bianconi, Ginestra; Rotzschke, Olaf
2010-09-01
The mapping between genotype and phenotype is encoded in the complex web of epistatic interaction between genetic loci. In this rugged fitness landscape, recombination processes, which tend to increase variation in the population, compete with selection processes that tend to reduce genetic variation. Here, we show that the Bose-Einstein distribution describe the multiple stationary states of a diploid population under this multiloci evolutionary dynamics. Moreover, the evolutionary process might undergo an interesting condensation phase transition in the universality class of a Bose-Einstein condensation when a finite fraction of pairs of linked loci is fixed into given allelic states. Below this phase transition the genetic variation within a species is significantly reduced and only maintained by the remaining polymorphic loci.
Phase Separation and Dynamics of Trapped Two-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Proukakis, Np; Lee, Kl; Edmonds, M.; Liu, I.-K.; Jorgensen, Nb; Wacker, L.; Arlt, Jj
2016-05-01
Two-component Bose-Einstein condensates (BECs) are an attractive system to study the non-equilibrium dynamics of interacting quantum gases. We recently formulated a self-consistent kinetic model to study such systems at finite-temperature, where both components are partially-condensed. The BECs and the thermal atoms are coupled together through both the mean-field interactions and all possible collisional processes. We demonstrate the potential dominance of an energy-conserving exchange collision involving a BEC atom and a thermal atom from different components, and discuss the control of the hydrodynamicity through variations of temperature, trap frequencies and trap geometries. Numerically analysing the miscibility-immiscibility phase diagram for the trapped 87Rb-39K experimental system, we demonstrate deviations from the simple (homogeneous) interaction strength criterion (g122 /g11g22 = 1), with the transition boundary depending on the BEC atom numbers. We propose the experimental mapping of this boundary by monitoring the damping rate of the dipole oscillations, supported by detailed numerical simulations at zero and finite temperatures. Acknowledge: EPSRC (Grant No. EP/K03250X/1).
Dynamics and thermalization of a Bose-Einstein condensate in a Sinai-oscillator trap
NASA Astrophysics Data System (ADS)
Ermann, Leonardo; Vergini, Eduardo; Shepelyansky, Dima L.
2016-07-01
We study numerically the evolution of Bose-Einstein condensate in the Sinai-oscillator trap described by the Gross-Pitaevskii equation in two dimensions. In the absence of interactions, this trap mimics the properties of Sinai billiards where the classical dynamics is chaotic and the quantum evolution is described by generic properties of quantum chaos and random matrix theory. We show that, above a certain border, the nonlinear interactions between atoms lead to the emergence of dynamical thermalization which generates the statistical Bose-Einstein distribution over eigenmodes of the system without interactions. Below the thermalization border, the evolution remains quasi-integrable. Such a Sinai-oscillator trap, formed by the oscillator potential and a repulsive disk located in the vicinity of the center, had been already realized in first experiments with the Bose-Einstein condensate formation by Ketterle group in 1995 and we argue that it can form a convenient test bed for experimental investigations of dynamical of thermalization. Possible links and implications for Kolmogorov turbulence in absence of noise are also discussed.
Composite structure of vortices in two-component Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Ivashin, Anatoly P.; Poluektov, Yuri M.
2015-10-01
In contrast to one-component Bose-Einstein condensate case, the vortices in two-component condensate can have various complicated structures. The vortices in a space-homogeneous Bose-Einstein condensate have been studied in this paper. It is shown that the vortex structure is described by three dimensionless parameters. This is totally different from the usual one-component condensate case,where an isolated vortex is described by a parameterless dimensionless equation. The two-component vortex structure strongly depends on the sign of "interaction" constant of the components. A few types of vortices with different qualitative structure are explored. We show that the "super-density vortices" can exist, when the "interaction" constant is positive. The "super-density vortices" have the near-axis density greater than the equilibrium density of a homogeneous space Bose-Einstein condensate. We also show that the vortices with opposite direction of the condensate component rotation near the axis and far off the axis can exist.
Two-dimensional solitons in dipolar Bose-Einstein condensates with spin-orbit coupling
NASA Astrophysics Data System (ADS)
Jiang, Xunda; Fan, Zhiwei; Chen, Zhaopin; Pang, Wei; Li, Yongyao; Malomed, Boris A.
2016-02-01
We report families of two-dimensional (2D) composite solitons in spinor dipolar Bose-Einstein condensates, with two localized components linearly mixed by the spin-orbit coupling (SOC), and the intrinsic nonlinearity represented by the dipole-dipole interaction (DDI) between atomic magnetic moments polarized in plane by an external magnetic field. Recently, stable solitons were predicted in the form of semivortices (composites built of coupled fundamental and vortical components) in the 2D system combining the SOC and contact attractive interactions. Replacing the latter by the anisotropic long-range DDI, we demonstrate that, for a fixed norm of the soliton, the system supports a continuous family of stable spatially asymmetric vortex solitons (AVSs), parameterized by an offset of the pivot of the vortical component relative to its fundamental counterpart. The offset is limited by a certain maximum value, while the energy of the AVS practically does not depend on the offset. At small values of the norm, the vortex solitons are subject to a weak oscillatory instability. In the present system, with the Galilean invariance broken by the SOC, the composite solitons are set in motion by a kick the strength of which exceeds a certain depinning value. The kicked solitons feature a negative effective mass, drifting along a spiral trajectory opposite to the direction of the kick. A critical angular velocity, up to which the semivortices may follow rotation of the polarizing magnetic field, is found too.
Exploring matter-wave dynamics with a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Chang, Rockson
Bose-Einstein condensates of dilute gases provide a rich and versatile platform to study both single-particle and many-body quantum phenomena. This thesis describes several experiments using a Bose-Einstein condensate of Rb-87 as a model system to study novel matter-wave effects that traditionally arise in vastly different systems, yet are difficult to access. We study the scattering of a particle from a repulsive potential barrier in the non-asymptotic regime, for which the collision dynamics are on-going. Using a Bose-Einstein condensate interacting with a sharp repulsive potential, two distinct transient scattering effects are observed: one due to the momentary deceleration of particles atop the barrier, and one due to the abrupt discontinuity in phase written on the wavepacket in position-space, akin to quantum reflection. Both effects lead to a redistribution of momenta, resulting in a rich interference pattern that may be used to reconstruct the single-particle wavefunction. In a second experiment, we study the response of a particle in a periodic potential to an applied force. By abruptly applying an external force to a Bose-Einstein condensate in a one-dimensional optical lattice, we show that the initial response of a particle in a periodic potential is in fact characterized by the bare mass, and only over timescales long compared to that of interband dynamics is the usual effective mass an appropriate description. This breakdown of the effective mass description on fast timescales is difficult to observe in traditional solid state systems due to their large bandgaps and fast timescale of interband dynamics. Both these experiments make use of the condensate's long coherence length, and the ability to shape and modulate the external potential on timescales fast compared to the particle dynamics, allowing for observation of novel matter-wave effects.
Long-Range Correlations of Density in a Bose-Einstein Condensate Expanding in a Random Potential
Cherroret, N.; Skipetrov, S. E.
2008-11-07
We study correlations of atomic density in a weakly interacting Bose-Einstein condensate, expanding diffusively in a random potential. We show that these correlations are long range and that they are strongly enhanced at long times. The density at distant points exhibits negative correlations.
Bose-Einstein condensation of dark matter solves the core/cusp problem
Harko, T.
2011-05-01
We analyze the observed properties of dwarf galaxies, which are dark matter dominated astrophysical objects, by assuming that dark matter is in the form of a strongly-coupled, dilute Bose-Einstein condensate. The basic astrophysical properties of the condensate (density profile, rotational velocity, and mass profile, respectively), are derived from a variational principle. To test the validity of the model we compare first the tangential velocity equation of the model with a sample of eight rotation curves of dwarf galaxies. We find a good agreement between the theoretically predicted rotation curves (without any baryonic component) and the observational data. The mean value of the logarithmic inner slope of the mass density profile of dwarf galaxies is also obtained, and it is shown that the observed value of this parameter is in agreement with the theoretical results. The predictions of the Bose-Einstein condensate model are also systematically compared with the predictions of the standard Cold Dark Matter model. The non-singular density profiles of the Bose-Einstein condensed dark matter generally show the presence of an extended core, whose presence is due to the strong interaction between dark matter particles.
BCS condensate as a special case of the Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Batle, J.; Casas, M.; Fortes, M.; Solís, M. A.; de Llano, M.; Salazar, A.; Valladares, A. A.; Rojo, O.
2001-03-01
Rather general separable interfermionic interactions with sufficient attraction to bind fermions into (bosonic) Cooper pairs (CPs) give [1], in 2D or 3D, a center-of-mass-momentum(CMM)-dependent CP binding energy that is quadratic for any coupling strictly only in the limit of zero Fermi energy, i.e., when the Fermi sea disappears and one is in vacuum. Otherwise, this "dispersion relation" is linear to good approximation---and perfectly so in weak to moderate coupling. Moreover, the CPs break up beyond a certain CMM which vanishes in the zero coupling limit. As a result, the condensate of BCS theory (which generally neglects nonzero CMM CPs) appears to be a special case of the Bose-Einstein condensate of a boson-fermion binary mixture. Chemical and thermal equilibrium in the mixture gives rise [2] to a boson number which is strongly coupling- and temperature-dependent, and generally leads to transition temperatures substantially greater than those predicted by BCS theory. [1] S.K. Adhikari et al., Physica C (in press) and Phys. Rev. B 62 (2000) 8671; M. Casas et al., Physica C 295 (1998) 93; M. Casas et al., Phys. Letters A 245 (1998) 55. [2] M. Casas et al., http://xxx.lanl.gov/abs/cond-mat/0003499.
Bose-Einstein condensation of nonzero-center-of-mass-momentum Cooper pairs
NASA Astrophysics Data System (ADS)
Batle, J.; Casas, M.; Fortes, M.; Solís, M. A.; de Llano, M.; Valladares, A. A.; Rojo, O.
2001-11-01
Cooper pair (CP) binding with both zero and nonzero center-of-mass momenta (CMM) is studied with a set of renormalized equations assuming a short-ranged (attractive) pairwise interfermion interaction. Expanding the associated dispersion relation in 2D in powers of the CMM, in weak-to-moderate coupling a term linear in the CMM dominates the pair excitation energy, while the quadratic behavior usually assumed in Bose-Einstein (BE) condensation studies prevails for any coupling only in the limit of zero Fermi velocity when the Fermi sea disappears, i.e., in vacuum. In 3D this same behavior is observed numerically. The linear term, moreover, exhibits CP breakup beyond a threshold CMM value which vanishes with coupling. This makes all the excited (nonzero-CMM) BE levels with preformed CPs collapse into a single ground level so that a BCS condensate (where only zero CMM CPs are usually allowed) appears in zero coupling to be a special case in either 2D or 3D of the BE condensate of linear-dispersion-relation CPs.
Rotating trapped Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Fetter, A. L.
2008-01-01
Trapped Bose-Einstein condensates (BECs) differ considerably from the standard textbook example of a uniform Bose gas. In an isotropic harmonic potential V( r) = ½ Mω2 r 2, the single-particle ground state introduces a new intrinsic scale of length [the ground-state size d = √ ℏ/( Mω)] and energy [the ground-state energy E 0 = frac{3} {2} ℏω]. When the trap rotates at a low angular velocity, the behavior of a single vortex illustrates the crucial role of discrete quantized vorticity. For more rapid rotation, the condensate contains a vortex array. The resulting centrifugal forces expand the condensate radially and shrink it axially; thus, the condensate becomes effectively two dimensional. If the external rotation speed approaches the frequency of the radial harmonic confining potential, the condensate enters the "lowest-Landau-level" regime, and a simple description again becomes possible. Eventually, the system is predicted to make a quantum phase transition to a highly correlated state analogous to the fractional quantum Hall states of electrons in a strong magnetic field.
Nonlinear phenomena in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Carr, Lincoln D.
2008-05-01
We present a medley of results from the last three years on nonlinear phenomena in BECs [1]. These include exact dynamics of multi-component condensates in optical lattices [2], vortices and ring solitons [3], macroscopic quantum tunneling [4], nonlinear band theory [5], and a pulsed atomic soliton laser [6]. 1. Emergent Nonlinear Phenomena in Bose-Einstein Condensates: Theory and Experiment, ed. P. G. Kevrekidis, D. J. Frantzeskakis, and R. Carretero-Gonzalez (Springer-Verlag, 2008). 2. R. Mark Bradley, James E. Bernard, and L. D. Carr, e-print arXiv:0711.1896 (2007). 3. G. Herring, L. D. Carr, R. Carretero-Gonzalez, P. G. Kevrekidis, D. J. Frantzeskakis, Phys. Rev. A in press, e-print arXiv:0709.2193 (2007); L. D. Carr and C. W. Clark, Phys. Rev. A v. 74, p.043613 (2006); L. D. Carr and C. W. Clark, Phys. Rev. Lett. v. 97, p.010403 (2006). 4. L. D. Carr, M. J. Holland, and B. A. Malomed, J. Phys. B: At. Mol. Opt. Phys., v.38, p.3217 (2005) 5. B. T. Seaman, L. D. Carr, and M. J. Holland, Phys. Rev. A, v. 71, p.033622 (2005). 6. L. D. Carr and J. Brand, Phys. Rev. A, v.70, p.033607 (2004); L. D. Carr and J. Brand, Phys. Rev. Lett., v.92, p.040401 (2004).
Entanglement of two-mode Bose-Einstein condensates
Hines, Andrew P.; McKenzie, Ross H.; Milburn, Gerard J.
2003-01-01
We investigate the entanglement characteristics of two general bimodal Bose-Einstein condensates--a pair of tunnel-coupled Bose-Einstein condensates and the atom-molecule Bose-Einstein condensate. We argue that the entanglement is only physically meaningful if the system is viewed as a bipartite system, where the subsystems are the two modes. The indistinguishibility of the particles in the condensate means that the atomic constituents are physically inaccessible and, thus, the degree of entanglement between individual particles, unlike the entanglement between the modes, is not experimentally relevant so long as the particles remain in the condensed state. We calculate the entanglement between the two modes for the exact ground state of the two bimodal condensates and consider the dynamics of the entanglement in the tunnel-coupled cas000.
Spin-orbit-coupled Bose-Einstein condensates.
Lin, Y-J; Jiménez-García, K; Spielman, I B
2011-03-01
Spin-orbit (SO) coupling--the interaction between a quantum particle's spin and its momentum--is ubiquitous in physical systems. In condensed matter systems, SO coupling is crucial for the spin-Hall effect and topological insulators; it contributes to the electronic properties of materials such as GaAs, and is important for spintronic devices. Quantum many-body systems of ultracold atoms can be precisely controlled experimentally, and would therefore seem to provide an ideal platform on which to study SO coupling. Although an atom's intrinsic SO coupling affects its electronic structure, it does not lead to coupling between the spin and the centre-of-mass motion of the atom. Here, we engineer SO coupling (with equal Rashba and Dresselhaus strengths) in a neutral atomic Bose-Einstein condensate by dressing two atomic spin states with a pair of lasers. Such coupling has not been realized previously for ultracold atomic gases, or indeed any bosonic system. Furthermore, in the presence of the laser coupling, the interactions between the two dressed atomic spin states are modified, driving a quantum phase transition from a spatially spin-mixed state (lasers off) to a phase-separated state (above a critical laser intensity). We develop a many-body theory that provides quantitative agreement with the observed location of the transition. The engineered SO coupling--equally applicable for bosons and fermions--sets the stage for the realization of topological insulators in fermionic neutral atom systems.
Symmetry breaking and singularity structure in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Commeford, K. A.; Garcia-March, M. A.; Ferrando, A.; Carr, Lincoln D.
2012-08-01
We determine the trajectories of vortex singularities that arise after a single vortex is broken by a discretely symmetric impulse in the context of Bose-Einstein condensates in a harmonic trap. The dynamics of these singularities are analyzed to determine the form of the imprinted motion. We find that the symmetry-breaking process introduces two effective forces: a repulsive harmonic force that causes the daughter trajectories to be ejected from the parent singularity and a Magnus force that introduces a torque about the axis of symmetry. For the analytical noninteracting case we find that the parent singularity is reconstructed from the daughter singularities after one period of the trapping frequency. The interactions between singularities in the weakly interacting system do not allow the parent vortex to be reconstructed. Analytic trajectories were compared to the actual minima of the wave function, showing less than 0.5% error for an impulse strength of v=0.00005. We show that these solutions are valid within the impulse regime for various impulse strengths using numerical integration of the Gross-Pitaevskii equation. We also show that the actual duration of the symmetry-breaking potential does not significantly change the dynamics of the system as long as the strength is below v=0.0005.
Coupling a single electron to a Bose-Einstein condensate.
Balewski, Jonathan B; Krupp, Alexander T; Gaj, Anita; Peter, David; Büchler, Hans Peter; Löw, Robert; Hofferberth, Sebastian; Pfau, Tilman
2013-10-31
The coupling of electrons to matter lies at the heart of our understanding of material properties such as electrical conductivity. Electron-phonon coupling can lead to the formation of a Cooper pair out of two repelling electrons, which forms the basis for Bardeen-Cooper-Schrieffer superconductivity. Here we study the interaction of a single localized electron with a Bose-Einstein condensate and show that the electron can excite phonons and eventually trigger a collective oscillation of the whole condensate. We find that the coupling is surprisingly strong compared to that of ionic impurities, owing to the more favourable mass ratio. The electron is held in place by a single charged ionic core, forming a Rydberg bound state. This Rydberg electron is described by a wavefunction extending to a size of up to eight micrometres, comparable to the dimensions of the condensate. In such a state, corresponding to a principal quantum number of n = 202, the Rydberg electron is interacting with several tens of thousands of condensed atoms contained within its orbit. We observe surprisingly long lifetimes and finite size effects caused by the electron exploring the outer regions of the condensate. We anticipate future experiments on electron orbital imaging, the investigation of phonon-mediated coupling of single electrons, and applications in quantum optics.
Nonlinear Phenomena in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Carr, Lincoln D.
2008-03-01
We present a medley of results from the last three years on nonlinear phenomena in BECs [1]. These include exact dynamics of multi-component condensates in optical lattices [2], vortices and ring solitons [3], macroscopic quantum tunneling [4], nonlinear band theory [5], and a pulsed atomic soliton laser [6]. 1. Emergent Nonlinear Phenomena in Bose-Einstein Condensates: Theory and Experiment, ed. P. G. Kevrekidis, D. J. Frantzeskakis, and R. Carretero-Gonzalez (Springer-Verlag, to appear, 2008) -- see L. D. Carr and Joachim Brand, e-print arXiv:0705.1139 (2007); Joachim Brand, L. D. Carr, B. P. Anderson, e-print arXiv:0705.1341 (2007). 2. R. Mark Bradley, James E. Bernard, and L. D. Carr, e-print arXiv:0711.1896 (2007). 3. G. Herring, L. D. Carr, R. Carretero-Gonzalez, P. G. Kevrekidis, D. J. Frantzeskakis, e-print arXiv:0709.2193 (2007); L. D. Carr and C. W. Clark, Phys. Rev. A v. 74, p.043613 (2006); L. D. Carr and C. W. Clark, Phys. Rev. Lett. v. 97, p.010403 (2006). 4. L. D. Carr, M. J. Holland, and B. A. Malomed, J. Phys. B: At. Mol. Opt. Phys., v.38, p.3217 (2005) 5. B. T. Seaman, L. D. Carr, and M. J. Holland, Phys. Rev. A, v. 71, p.033622 (2005). 6. L. D. Carr and J. Brand, Phys. Rev. A, v.70, p.033607 (2004); L. D. Carr and J. Brand, Phys. Rev. Lett., v.92, p.040401 (2004).
Quantum and thermal fluctuations of trapped Bose-Einstein condensates
Kruglov, V.I.; Collett, M.J.; Olsen, M.K.
2005-09-15
We quantize a semiclassical system defined by the Hamiltonian obtained from the asymptotic self-similar solution of the Gross-Pitaevskii equation for a trapped Bose-Einstein condensate with a linear gain term. On the basis of a Schroedinger equation derived in a space of ellipsoidal parameters, we analytically calculate the quantum mechanical and thermal variance in the ellipsoidal parameters for Bose-Einstein condensates in various shapes of trap. We show that, except for temperatures close to zero, dimensionless dispersions do not depend on the frequencies of the trap and they have the same dependence on dimensionless temperatures.
Modeling Bose-Einstein correlations via elementary emitting cells
Utyuzh, Oleg; Wilk, Grzegorz; Wlodarczyk, Zbigniew
2007-04-01
We propose a method of numerical modeling Bose-Einstein correlations by using the notion of the elementary emitting cell (EEC). They are intermediary objects containing identical bosons and are supposed to be produced independently during the hadronization process. Only bosons in the EEC, which represents a single quantum state here, are subjected to the effects of Bose-Einstein (BE) statistics, which forces them to follow a geometrical distribution. There are no such effects between particles from different EECs. We illustrate our proposition by calculating a representative number of typical distributions and discussing their sensitivity to EECs and their characteristics.
Impurities in Bose-Einstein Condensates: From Polaron to Soliton.
Shadkhoo, Shahriar; Bruinsma, Robijn
2015-09-25
We propose that impurities in a Bose-Einstein condensate which is coupled to a transversely laser-pumped multimode cavity form an experimentally accessible and analytically tractable model system for the study of impurities solvated in correlated liquids and the breakdown of linear-response theory [corrected]. As the strength of the coupling constant between the impurity and the Bose-Einstein condensate is increased, which is possible through Feshbach resonance methods, the impurity passes from a large to a small polaron state, and then to an impurity-soliton state. This last transition marks the breakdown of linear-response theory.
Space-time curvature signatures in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Matos, Tonatiuh; Gomez, Eduardo
2015-05-01
We derive a generalized Gross-Pitaevski (GP) equation for a Bose Einstein Condensate (BEC) immersed in a weak gravitational field starting from the covariant Complex Klein-Gordon field in a curved space-time. We compare it with the traditional GP equation where the gravitational field is added by hand as an external potential. We show that there is a small difference of order gz/c2 between them that could be measured in the future using Bose-Einstein Condensates. This represents the next order correction to the Newtonian gravity in a curved space-time.
Growth of perturbations in an expanding universe with Bose-Einstein condensate dark matter
NASA Astrophysics Data System (ADS)
Chavanis, P. H.
2012-01-01
We study the growth of perturbations in an expanding Newtonian universe with Bose-Einstein condensate (BEC) dark matter. We first ignore special relativistic effects and derive a differential equation that governs the evolution of the density contrast in the linear regime. This equation, which takes quantum pressure and self-interaction into account, can be solved analytically in several cases. We argue that an attractive self-interaction can enhance the Jeans instability and fasten the formation of structures. Then, we take pressure effects (coming from special relativity) into account in the evolution of the cosmic fluid and add the contribution of radiation, baryons, and dark energy (cosmological constant). For BEC dark matter with repulsive self-interaction (positive pressure) the scale factor increases more rapidly than in the standard ΛCDM model where dark matter is pressureless, while it increases less rapidly for BEC dark matter with attractive self-interaction (negative pressure). We study the linear development of the perturbations in these two cases and show that the perturbations grow faster in BEC dark matter than in pressureless dark matter. Finally, we consider a "dark fluid" with a generalized equation of state p = (αρ + kρ2)c2 having a component p = kρ2c2 similar to BEC dark matter and a component p = αρc2 mimicking the effect of the cosmological constant (dark energy). We find optimal parameters that give good agreement with the standard ΛCDM model that assumes a finite cosmological constant.
Rabi-coupled countersuperflow in binary Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Usui, Ayaka; Takeuchi, Hiromitsu
2015-06-01
We show theoretically that periodic density patterns are stabilized in two counterpropagating Bose-Einstein condensates of atoms in different hyperfine states under Rabi coupling. In the presence of coupling, the relative velocity between the two components is localized around density depressions in quasi-one-dimensional systems. When the relative velocity is sufficiently small, the periodic pattern reduces to a periodic array of topological solitons as kinks of the relative phase. According to our variational and numerical analyses, the soliton solution is well characterized by the soliton width and density depression. We demonstrate the dependence of the depression and width on the Rabi frequency and the coupling constant of the intercomponent density-density interactions. The periodic pattern of the relative phase transforms continuously from a soliton array to a sinusoidal pattern as the period becomes smaller than the soliton width. These patterns become unstable when the localized relative velocity exceeds a critical value. The stability-phase diagram of this system is evaluated with a stability analysis of countersuperflow, by taking into account the finite-size effect owing to the density depression.
Shock Waves in a Bose-Einstein Condensate
NASA Technical Reports Server (NTRS)
Kulikov, Igor; Zak, Michail
2005-01-01
A paper presents a theoretical study of shock waves in a trapped Bose-Einstein condensate (BEC). The mathematical model of the BEC in this study is a nonlinear Schroedinger equation (NLSE) in which (1) the role of the wave function of a single particle in the traditional Schroedinger equation is played by a space- and time-dependent complex order parameter (x,t) proportional to the square root of the density of atoms and (2) the atoms engage in a repulsive interaction characterized by a potential proportional to | (x,t)|2. Equations that describe macroscopic perturbations of the BEC at zero temperature are derived from the NLSE and simplifying assumptions are made, leading to equations for the propagation of sound waves and the transformation of sound waves into shock waves. Equations for the speeds of shock waves and the relationships between jumps of velocity and density across shock fronts are derived. Similarities and differences between this theory and the classical theory of sound waves and shocks in ordinary gases are noted. The present theory is illustrated by solving the equations for the example of a shock wave propagating in a cigar-shaped BEC.
Topological interface physics in spinor Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Borgh, Magnus; Ruostekoski, Janne
2013-05-01
We present an experimentally viable scheme whereby the physics of coherent interfaces between topologically distinct regions can be studied in an atomic quantum gas. The interface engineering is achieved using the internal spin structures of atoms together with local control over interaction strengths. We consider a coherent interface between polar and ferromagnetic regions of a spin-1 Bose-Einstein condensate and show that defects representing different topologies can connect continuously across the boundary. We show that energy minimization leads to nontrivial interface-crossing defect structures, demonstrating how the method can be used to study stability properties of field-theoretical solitons. We demonstrate, e.g., the formation of a half-quantum vortex arch, an Alice arch, on the interface, exhibiting the topological charge of a point defect. We also demonstrate an energetically stable connection of a coreless vortex to two half-quantum vortices. Our method can be extended to study interface physics in spin-2 and spin-3 BECs with richer phenomenology, or in strongly correlated optical-lattice systems. We acknowledge financial support from the Leverhulme Trust.
Manipulating localized matter waves in multicomponent Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Manikandan, K.; Muruganandam, P.; Senthilvelan, M.; Lakshmanan, M.
2016-03-01
We analyze vector localized solutions of two-component Bose-Einstein condensates (BECs) with variable nonlinearity parameters and external trap potentials through a similarity transformation technique which transforms the two coupled Gross-Pitaevskii equations into a pair of coupled nonlinear Schrödinger equations with constant coefficients under a specific integrability condition. In this analysis we consider three different types of external trap potentials: a time-independent trap, a time-dependent monotonic trap, and a time-dependent periodic trap. We point out the existence of different interesting localized structures; namely, rogue waves, dark- and bright-soliton rogue waves, and rogue-wave breatherlike structures for the above three cases of trap potentials. We show how the vector localized density profiles in a constant background get deformed when we tune the strength of the trap parameter. Furthermore, we investigate the nature of the trajectories of the nonautonomous rogue waves. We also construct the dark-dark rogue wave solution for the repulsive-repulsive interaction of two-component BECs and analyze the associated characteristics for the three different kinds of traps. We then deduce single-, two-, and three-composite rogue waves for three-component BECs and discuss the correlated characteristics when we tune the strength of the trap parameter for different trap potentials.
Vortices in spin-orbit-coupled Bose-Einstein condensates
Radic, J.; Sedrakyan, T. A.; Galitski, V.; Spielman, I. B.
2011-12-15
Realistic methods to create vortices in spin-orbit-coupled Bose-Einstein condensates are discussed. It is shown that, contrary to common intuition, rotation of the trap containing a spin-orbit condensate does not lead to an equilibrium state with static vortex structures but gives rise instead to nonequilibrium behavior described by an intrinsically time-dependent Hamiltonian. We propose here the following alternative methods to induce thermodynamically stable static vortex configurations: (i) to rotate both the lasers and the anisotropic trap and (ii) to impose a synthetic Abelian field on top of synthetic spin-orbit interactions. Effective Hamiltonians for spin-orbit condensates under such perturbations are derived for most currently known realistic laser schemes that induce synthetic spin-orbit couplings. The Gross-Pitaevskii equation is solved for several experimentally relevant regimes. The new interesting effects include spatial separation of left- and right-moving spin-orbit condensates, the appearance of unusual vortex arrangements, and parity effects in vortex nucleation where the topological excitations are predicted to appear in pairs. All these phenomena are shown to be highly nonuniversal and depend strongly on a specific laser scheme and system parameters.
Tunable Bistability in Hybrid Bose-Einstein Condensate Optomechanics
Yasir, Kashif Ammar; Liu, Wu-Ming
2015-01-01
Cavity-optomechanics, a rapidly developing area of research, has made a remarkable progress. A stunning manifestation of optomechanical phenomena is in exploiting the mechanical effects of light to couple the optical degree of freedom with mechanical degree of freedom. In this report, we investigate the controlled bistable dynamics of such hybrid optomechanical system composed of cigar-shaped Bose-Einstein condensate (BEC) trapped inside high-finesse optical cavity with one moving-end mirror and is driven by a single mode optical field. The numerical results provide evidence for controlled optical bistability in optomechanics using transverse optical field which directly interacts with atoms causing the coupling of transverse field with momentum side modes, exited by intra-cavity field. This technique of transverse field coupling is also used to control bistable dynamics of both moving-end mirror and BEC. The report provides an understanding of temporal dynamics of moving-end mirror and BEC with respect to transverse field. Moreover, dependence of effective potential of the system on transverse field has also been discussed. To observe this phenomena in laboratory, we have suggested a certain set of experimental parameters. These findings provide a platform to investigate the tunable behavior of novel phenomenon like electromagnetically induced transparency and entanglement in hybrid systems. PMID:26035206
Manipulating localized matter waves in multicomponent Bose-Einstein condensates.
Manikandan, K; Muruganandam, P; Senthilvelan, M; Lakshmanan, M
2016-03-01
We analyze vector localized solutions of two-component Bose-Einstein condensates (BECs) with variable nonlinearity parameters and external trap potentials through a similarity transformation technique which transforms the two coupled Gross-Pitaevskii equations into a pair of coupled nonlinear Schrödinger equations with constant coefficients under a specific integrability condition. In this analysis we consider three different types of external trap potentials: a time-independent trap, a time-dependent monotonic trap, and a time-dependent periodic trap. We point out the existence of different interesting localized structures; namely, rogue waves, dark- and bright-soliton rogue waves, and rogue-wave breatherlike structures for the above three cases of trap potentials. We show how the vector localized density profiles in a constant background get deformed when we tune the strength of the trap parameter. Furthermore, we investigate the nature of the trajectories of the nonautonomous rogue waves. We also construct the dark-dark rogue wave solution for the repulsive-repulsive interaction of two-component BECs and analyze the associated characteristics for the three different kinds of traps. We then deduce single-, two-, and three-composite rogue waves for three-component BECs and discuss the correlated characteristics when we tune the strength of the trap parameter for different trap potentials.
Manipulating localized matter waves in multicomponent Bose-Einstein condensates.
Manikandan, K; Muruganandam, P; Senthilvelan, M; Lakshmanan, M
2016-03-01
We analyze vector localized solutions of two-component Bose-Einstein condensates (BECs) with variable nonlinearity parameters and external trap potentials through a similarity transformation technique which transforms the two coupled Gross-Pitaevskii equations into a pair of coupled nonlinear Schrödinger equations with constant coefficients under a specific integrability condition. In this analysis we consider three different types of external trap potentials: a time-independent trap, a time-dependent monotonic trap, and a time-dependent periodic trap. We point out the existence of different interesting localized structures; namely, rogue waves, dark- and bright-soliton rogue waves, and rogue-wave breatherlike structures for the above three cases of trap potentials. We show how the vector localized density profiles in a constant background get deformed when we tune the strength of the trap parameter. Furthermore, we investigate the nature of the trajectories of the nonautonomous rogue waves. We also construct the dark-dark rogue wave solution for the repulsive-repulsive interaction of two-component BECs and analyze the associated characteristics for the three different kinds of traps. We then deduce single-, two-, and three-composite rogue waves for three-component BECs and discuss the correlated characteristics when we tune the strength of the trap parameter for different trap potentials. PMID:27078349
Rapidly rotating Bose-Einstein condensates in strongly anharmonic traps
Correggi, M.; Rindler-Daller, T.; Yngvason, J.
2007-04-15
We study a rotating Bose-Einstein condensate in a strongly anharmonic trap (flat trap with a finite radius) in the framework of two-dimensional Gross-Pitaevskii theory. We write the coupling constant for the interactions between the gas atoms as 1/{epsilon}{sup 2} and we are interested in the limit {epsilon}{yields}0 (Thomas-Fermi limit) with the angular velocity {omega} depending on {epsilon}. We derive rigorously the leading asymptotics of the ground state energy and the density profile when {omega} tends to infinity as a power of 1/{epsilon}. If {omega}({epsilon})={omega}{sub 0}/{epsilon} a ''hole'' (i.e., a region where the density becomes exponentially small as 1/{epsilon}{yields}{infinity}) develops for {omega}{sub 0} above a certain critical value. If {omega}({epsilon})>>1/{epsilon} the hole essentially exhausts the container and a ''giant vortex'' develops with the density concentrated in a thin layer at the boundary. While we do not analyze the detailed vortex structure we prove that rotational symmetry is broken in the ground state for const vertical bar log {epsilon} vertical bar <{omega}({epsilon}) < or approx. const/{epsilon}.
Route to Quantum Turbulence in Trapped Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Allen, A.; Parker, Nick; Proukakis, Nick; Barenghi, Carlo
2013-05-01
Turbulence in superfluid Helium has been the subject of many experimental and theoretical investigations (for review see e.g. L. Skrbek and K.R. Sreenivasan, Phys. of Fluids 24, 011301 (2012)) and recently, experimentalists have been able to visualize vortex lines, reconnection events and Kelvin waves (E. Fonda et al. arXiv:1210.5194). Weakly interacting Bose-Einstein condensates however, present a unique opportunity to resolve the structure of vortices and in turn study the dynamics of a vortex tangle (as has recently been created in an atomic cloud E.A.L. Henn et al. Phys. Rev. Lett 103, 04301 (2009)). We investigate ways of generating turbulence in atomic systems by numerically stirring the condensate using a Gaussian `spoon' (analogous to a laser beam in the experiments), and study the isotropy of the resulting vortex tangle depending on whether the path the spoon stirs is circular or random. We model the system using the Gross-Pitaevskii Equation and extend our analysis to finite temperature using the Zaremba-Nikuni-Griffin (ZNG) formalism (E. Zaremba et al. Jour. Low Temp. Phys. 116, 277 (1999)), whereby the full dynamics of the noncondensate atoms are described by a semiclassical Boltzmann equation.
Vortices and hysteresis in a rotating Bose-Einstein condensate with anharmonic confinement
Jackson, A.D.; Kavoulakis, G.M.
2004-08-01
We examine an effectively repulsive Bose-Einstein condensate of atoms that rotates in a quadratic-plus-quartic trapping potential. We investigate the phase diagram of the system as a function of the angular frequency of rotation and of the coupling constant, demonstrating that there are phase transitions between multiply and singly quantized vortex states. We also show that states of different circulation can be metastable and, as a result, the gas can exhibit hysteresis as the angular frequency of rotation of the trap is varied. The simplicity of the picture that emerges for small coupling strengths suggests that this system may be attractive for studies of phase transitions.
Stationary and nonstationary fluid flow of a bose-einstein condensate through a penetrable barrier.
Engels, P; Atherton, C
2007-10-19
We experimentally study the fluid flow induced by a broad, penetrable barrier moving through an elongated dilute gaseous Bose-Einstein condensate. The barrier is created by a laser beam swept through the condensate, and the resulting dipole potential can be either attractive or repulsive. We examine both cases and find regimes of stable and unstable fluid flow: At slow speeds of the barrier, the fluid flow is steady due to the superfluidity of the condensate. At intermediate speeds, we observe an unsteady regime in which the condensate gets filled with dark solitons. At faster speeds, soliton formation completely ceases, and a remarkable absence of excitation in the condensate is seen again.
Stability of a dipolar Bose-Einstein condensate in a one-dimensional lattice
Mueller, S.; Billy, J.; Henn, E. A. L.; Kadau, H.; Griesmaier, A.; Pfau, T.; Jona-Lasinio, M.; Santos, L.
2011-11-15
We show that in contrast with contact interacting gases, an optical lattice changes drastically the stability properties of a dipolar condensate, inducing a crossover from dipolar destabilization to dipolar stabilization for increasing lattice depths. Performing stability measurements on a {sup 52}Cr Bose-Einstein condensate in an interaction-dominated regime, repulsive dipolar interaction balances negative scattering lengths down to -17 Bohr radii. Our findings are in excellent agreement with mean-field calculations, revealing the important destabilizing role played by intersite dipolar interactions in deep lattices.
Oscillatory decay of a two-component bose-einstein condensate.
Kohler, Sigmund; Sols, Fernando
2002-08-01
We study the decay of a two-component Bose-Einstein condensate with negative effective interaction energy. With a decreasing atom number due to losses, the atom-atom interaction becomes less important and the system undergoes a transition from a bistable Josephson regime to the monostable Rabi regime, displaying oscillations in phase and number. We study the equations of motion and derive an analytical expression for the oscillation amplitude. A quantum trajectory simulation reveals that the classical description fails for low loss rates, as expected from analytical considerations. Observation of the proposed effect will provide evidence for negative effective interaction.
Nonlinear transport of Bose-Einstein condensates through waveguides with disorder
Paul, Tobias; Richter, Klaus; Schlagheck, Peter; Leboeuf, Patricio; Pavloff, Nicolas
2005-12-15
We study the coherent flow of a guided Bose-Einstein condensate incident over a disordered region of length L. We introduce a model of disordered potential that originates from magnetic fluctuations inherent to microfabricated guides. This model allows for analytical and numerical studies of realistic transport experiments. The repulsive interaction among the condensate atoms in the beam induces different transport regimes. Below some critical interaction (or for sufficiently small L) a stationary flow is observed. In this regime, the transmission decreases exponentially with increasing L. For strong interaction (or large L), the system displays a transition toward a time-dependent flow with an algebraic decay of the time-averaged transmission.
Bose-Einstein-condensate heating by atomic losses
Dziarmaga, Jacek; Sacha, Krzysztof
2003-10-01
Atomic Bose-Einstein condensate is heated by atomic losses. The losses act as a heat reservoir for the condensate. The condensate is approaching a state of thermal equilibrium with a thermal depletion ranging from 1% for a uniform three-dimensional (3D) condensate to around 13% for a quasi-1D condensate in a harmonic trap.
Stability analysis for n-component Bose-Einstein condensate
Roberts, David C.; Ueda, Masahito
2006-05-15
We derive the dynamic and thermodynamic stability conditions for dilute multicomponent Bose-Einstein condensates (BECs). These stability conditions, generalized for n-component BECs, are found to be equivalent and are shown to be consistent with the phase diagrams of two- and three-component condensates that are derived from energetic arguments.
Bose-Einstein correlation within the framework of hadronic mechanics
Burande, Chandrakant S.
2015-03-10
The Bose-Einstein correlation is the phenomenon in which protons and antiprotons collide at extremely high energies; coalesce one into the other resulting into the fireball of finite dimension. They annihilate each other and produces large number of mesons that remain correlated at distances very large compared to the size of the fireball. It was believed that Einstein’s special relativity and relativistic quantum mechanics are the valid frameworks to represent this phenomenon. Although, these frameworks are incomplete and require arbitrary parameters (chaoticity) to fit the experimental data which are prohibited by the basic axioms of relativistic quantum mechanics, such as that for the vacuum expectation values. Moreover, correlated mesons can not be treated as a finite set of isolated point-like particles because it is non-local event due to overlapping of wavepackets. Therefore, the Bose-Einstein correlation is incompatible with the axiom of expectation values of quantum mechanics. In contrary, relativistic hadronic mechanics constructed by Santilli allows an exact representation of the experimental data of the Bose-Einstein correlation and restore the validity of the Lorentz and Poincare symmetries under nonlocal and non-Hamiltonian internal effects. Further, F. Cardone and R. Mignani observed that the Bose-Einstein two-point correlation function derived by Santilli is perfectly matched with experimental data at high energy.
Emergent Gravitational Dynamics in Bose-Einstein Condensates
Sindoni, Lorenzo; Liberati, Stefano; Girelli, Florian
2009-12-15
We discuss a toy model for an emergent non-relativistic gravitational theory. Within a certain class of Bose-Einstein condensates, it is possible to show that, in a suitable regime, a modified version of non-relativistic Newtonian gravity does effectively describes the low energy dynamics of the coupled system condensate/quasi-particles.
Sabari, S; Jisha, Chandroth P; Porsezian, K; Brazhnyi, Valeriy A
2015-09-01
We study the stabilization properties of dipolar Bose-Einstein condensate by temporal modulation of short-range two-body interaction. Through both analytical and numerical methods, we analyze the mean-field Gross-Pitaevskii equation with short-range two-body and long-range, nonlocal, dipolar interaction terms. We derive the equation of motion and effective potential of the dipolar condensate by variational method. We show that there is an enhancement of the condensate stability due to the inclusion of dipolar interaction in addition to the two-body contact interaction. We also show that the stability of the dipolar condensate increases in the presence of time varying two-body contact interaction; the temporal modification of the contact interaction prevents the collapse of dipolar Bose-Einstein condensate. Finally we confirm the semi-analytical prediction through the direct numerical simulations of the governing equation.
NASA Astrophysics Data System (ADS)
Adhikari, S. K.
2016-08-01
We study the statics and dynamics of anisotropic, stable, bright and dark-in-bright dipolar quasi-two-dimensional Bose-Einstein condensate (BEC) solitons on a one-dimensional (1D) optical-lattice (OL) potential. These solitons mobile in a plane perpendicular to a 1D OL trap can have both repulsive and attractive contact interactions. Dark-in-bright solitons are the excited states of bright solitons. The solitons, when subjected to a small perturbation, exhibit sustained breathing oscillation. Dark-in-bright solitons can be created by phase imprinting a bright soliton. At medium velocities the collision between two solitons is found to be quasi-elastic. Results are demonstrated by a numerical simulation of the three-dimensional mean-field Gross-Pitaevskii equation in three spatial dimensions employing realistic interaction parameters for a dipolar 164Dy BEC.
Dynamic structure factor of a Bose-Einstein condensate in a one-dimensional optical lattice
Menotti, C.; Kraemer, M.; Stringari, S.; Pitaevskii, L.
2003-05-01
We study the effect of a one-dimensional periodic potential on the dynamic structure factor of an interacting Bose-Einstein condensate at zero temperature. We show that, due to phononic correlations, the excitation strength toward the first band develops a typical oscillating behavior as a function of the momentum transfer, and vanishes at even multiples of the Bragg momentum. The effects of interactions on the static structure factor are found to be significantly amplified by the presence of the optical potential. Our predictions can be tested in stimulated photon scattering experiments.
Exact soliton-on-plane-wave solutions for two-component Bose-Einstein condensates.
Li, Lu; Malomed, Boris A; Mihalache, Dumitru; Liu, W M
2006-06-01
By means of the Darboux transformation, we obtain analytical solutions for a soliton set on top of a plane-wave background in coupled Gross-Pitaevskii equations describing a binary Bose-Einstein condensate. We consider basic properties of the solutions with and without the cross interaction [cross phase modulation (XPM)] between the two components of the background. In the absence of the XPM, this solutions maintain properties of one-component condensates, such as the modulation instability (MI); in the presence of the cross interaction, the solutions exhibit different properties, such as restriction of the MI and soliton splitting.
Eliminating the mean-field shift in two-component bose-einstein condensates
Goldstein; Moore; Pu; Meystre
2000-12-11
We demonstrate that the nonlinear mean-field shift in a multicomponent Bose-Einstein condensate may be eliminated by controlling the two-body interaction coefficients. This modification can be achieved by engineering the environment of the condensate. We consider the case of a two-component condensate in a quasi-one-dimensional atomic waveguide, achieving modification of the atom-atom interactions by varying the transverse wave functions of the components. Eliminating the density-dependent phase shift represents a promising potential application for multicomponent condensates in atom interferometry and precision measurements.
Dark solitons in a two-component Bose-Einstein condensate.
Ohberg, P; Santos, L
2001-04-01
The creation and interaction of dark solitons in a two-component Bose-Einstein condensate is investigated. For a miscible case, the interaction of dark solitons in different components is studied. Various possible scenarios are presented, including the formation of a soliton-soliton bound pair. We also analyze the soliton propagation in the presence of domains, and show that a dark soliton can be transferred from one component to the other at the domain wall when it exceeds a critical velocity. For lower velocities multiple reflections within the domain are observed, where the soliton is evaporated and accelerated after each reflection until it finally escapes from the domain.
Photon-assisted tunneling of a driven two-mode Bose-Einstein condensate
Xie Qiongtao; Rong Shiguang; Zhong Honghua; Lu Gengbiao; Hai Wenhua
2010-08-15
We investigate the photon-assisted tunneling of a Bose-Einstein condensate in a periodically driven double-well potential. It is shown that the energy levels become nonequidistant due to the presence of the interatomic interaction, thereby leading to the occurrences of the fractional photon resonances. Depending on whether the resonance frequency shifts with the interatomic interaction, two distinct types of resonances are identified: nonshifting resonances and shifting resonances. In particular, certain nonshifting fractional resonances show an odd-even sensitivity to the atom number.
Collective oscillations in trapped Bose-Einstein-condensed gases in the presence of weak disorder
Falco, G. M.; Pelster, A.; Graham, R.
2007-07-15
The influence of a weak random potential on the collective modes of a trapped interacting Bose-Einstein condensate at zero temperature is calculated in the limit when the correlation length of the disorder is smaller than the healing length of the superfluid. The problem is solved in the Thomas-Fermi limit by generalizing the superfluid hydrodynamic equations to allow for the presence of weak disorder. We find that the disorder-induced frequency shifts of the low-energy excitations can be of the same order of magnitude as the beyond mean-field corrections in the normal interaction recently observed experimentally.
Mackie, Matt; Collin, Anssi; Javanainen, Juha
2005-01-01
Collective two-color photoassociation of a freely interacting {sup 87}Rb Bose-Einstein condensate is theoretically examined, focusing on stimulated Raman adiabatic passage (STIRAP) from an atomic to a stable molecular condensate. In particular, Drummond et al. [Phys. Rev. A. 65, 063619 (2002)] have predicted that particle-particle interactions can limit the efficiency of collective atom-molecule STIRAP, and that optimizing the laser parameters can partially overcome this limitation. We suggest that the molecular conversion efficiency can be further improved by treating the initial condensate density as an optimization parameter.
Schulte, T.; Drenkelforth, S.; Kruse, J.; Ertmer, W.; Arlt, J.; Sacha, K.; Zakrzewski, J.; Lewenstein, M.
2005-10-21
We investigate, both experimentally and theoretically, possible routes towards Anderson-like localization of Bose-Einstein condensates in disordered potentials. The dependence of this quantum interference effect on the nonlinear interactions and the shape of the disorder potential is investigated. Experiments with an optical lattice and a superimposed disordered potential reveal the lack of Anderson localization. A theoretical analysis shows that this absence is due to the large length scale of the disorder potential as well as its screening by the nonlinear interactions. Further analysis shows that incommensurable superlattices should allow for the observation of the crossover from the nonlinear screening regime to the Anderson localized case within realistic experimental parameters.
Mixtures of ultracold gases: Fermi sea and Bose-Einstein condensate of lithium isotopes
NASA Astrophysics Data System (ADS)
Schreck, F.
2003-03-01
This thesis presents studies of quantum degenerate atomic gases of fermionic ^6Li and bosonic ^7Li. Degeneracy is reached by evaporative cooling of ^7Li in a strongly confining magnetic trap. Since at low temperatures direct evaporative cooling is not possible for a polarized fermionic gas, ^6Li is sympathetically cooled by thermal contact with ^7Li. In a first series of experiments both isotopes are trapped in their low-field seeking higher hyperfine states. A Fermi degeneracy of T/T_F=0.25(5) is achieved for 10^5 fermions. For more than 300 atoms, the ^7Li condensate collapses, due to the attractive interatomic interaction in this state. This limits the degeneracy reached for both species. To overcome this limit, in a second series of experiments ^7Li and ^6Li atoms are transferred to their low field seeking lower hyperfine states, where the boson-boson interaction is repulsive but weak. The inter-isotope collisions are used to thermalize the mixture. A ^7Li Bose-Einstein condensate (BEC) of 10^4 atoms immersed in a Fermi sea is produced. The BEC is quasi-one-dimensional and the thermal fraction can be negligible. The measured degeneracies are T/T_C=T/T_F=0.2(1). The temperature is measured using the bosonic thermal fraction, which vanishes at the lowest temperatures, limiting our measurement sensitivity. In a third series of experiments, the bosons are transferred into an optical trap and their internal state is changed to |F=1,m_F=1rangle, the lowest energy state. A Feshbach resonance is detected and used to produce a BEC with tunable atomic interactions. When the effective interaction between atoms is tuned to be small and attractive, we observe the formation of a matter-wave bright soliton. Propagation of the soliton without spreading over a macroscopic distance of 1.1 mm is observed. Mélanges de gaz ultrafroids: mer de Fermi et condensat de Bose-Einstein des isotopes du lithium Cette thèse décrit l'étude des gaz de fermions ^6Li et de bosons ^7Li dans le
Kornilovitch, P E; Hague, J P
2015-02-25
Both FeSe and cuprate superconductors are quasi 2D materials with high transition temperatures and local fermion pairs. Motivated by such systems, we investigate real space pairing of fermions in an anisotropic lattice model with intersite attraction, V, and strong local Coulomb repulsion, U, leading to a determination of the optimal conditions for superconductivity from Bose-Einstein condensation. Our aim is to gain insight as to why high temperature superconductors tend to be quasi 2D. We make both analytically and numerically exact solutions for two body local pairing applicable to intermediate and strong V. We find that the Bose-Einstein condensation temperature of such local pairs pairs is maximal when hopping between layers is intermediate relative to in-plane hopping, indicating that the quasi 2D nature of unconventional superconductors has an important contribution to their high transition temperatures. PMID:25629425
Dynamics of Two-Component Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Baik, Eunsil
I explored the vortex dynamics in homonuclear species two-component Bose-Einstein condensates (BECs) based on the knowledge of vortex dynamics in one-component BECs. The vortex dynamics in BECs depends on the background fields induced by different external potentials and other vortices. The motion of vortices is numerically computed and the numerical results are compared to the theoretical formulas where possible. In the study of the vortex-vortex interaction dynamics in one-component BECs, a power law relationship between the motion of the vortices and their separation distance is depicted. In addition to that, the relationship between the linear and the angular velocities of the vortices is found to be similar to the relationship between the tangential and the angular velocities of classical fluid vortices. In the case of two-component BEC dynamics, two different cases are studied: one without atomic inter-conversion between the two components and the other with atomic inter-conversion. The stability analysis of the two-component BECs is conducted to identify the stable regions as well as the regions of mixed and separated states. When a vortex is seeded in one component, this vortex induces a hump in the other component at the same location as the vortex, which leads to the vortex-hump dynamics. The vortex-hump-vortex-hump interaction dynamics without atomic inter-conversion depicts a power law relation between the motion of vortex-humps and the separation distance; whereas, the vortex-hump-vortex-hump interaction dynamics with atomic inter-conversion reveals a more complex relation between the motion of vortex-humps and the separation distance.
Dynamics and stability of Bose-Einstein solitons in tilted optical lattices
Diaz, E.; Dominguez-Adame, F.; Gaul, C.; Lima, R. P. A.; Mueller, C. A.
2010-05-15
Bloch oscillations of Bose-Einstein condensates realize sensitive matter-wave interferometers. We investigate the dynamics and stability of bright-soliton wave packets in one-dimensional tilted optical lattices with a modulated mean-field interaction g(t). By means of a time-reversal argument, we prove the stability of Bloch oscillations of breathing solitons that would be quasistatically unstable. Floquet theory shows that these breathing solitons can be more stable against certain experimental perturbations than rigid solitons or even noninteracting wave packets.
Phase diagram of a rotating Bose-Einstein condensate with anharmonic confinement
Jackson, A.D.; Kavoulakis, G.M.; Lundh, E.
2004-05-01
We examine the phase diagram of an effectively repulsive Bose-Einstein condensate of atoms that rotates in a quadratic-plus-quartic potential. With use of a variational method we identify the three possible phases of the system as a function of the rotational frequency of the trap and of the coupling constant. The derived phase diagram is shown to be universal and partly exact in the limit of weak interactions and small anharmonicity. The variational results are found to be consistent with numerical solutions of the Gross-Pitaevskii equation.
Creation of a vortex in a Bose-Einstein condensate by superradiant scattering
Tasgin, M. E.; Muestecaplioglu, Oe. E.; You, L.
2011-12-15
The creation of a topological vortex by a superradiant scattering of a Laguerre-Gaussian (LG) beam off an atomic Bose-Einstein condensate (BEC) is theoretically investigated. It is shown that scattered superradiant radiation can be either in a Gaussian mode without angular momentum or in a LG mode with angular momentum. The conditions leading to these two qualitatively distinct regimes of superradiance are determined in terms of the width for the pump laser and the condensate size for the limiting cases where the recoil energy is both much smaller and larger than the atomic interaction energy.
Exact results on the two-particle Green's function of a Bose-Einstein condensate
Kita, Takafumi
2010-06-01
Starting from the Dyson-Beliaev and generalized Gross-Pitaevskii equations with an extra nonlocal potential, we derive an exact expression of the two-particle Green's function K lowbar for an interacting Bose-Einstein condensate in terms of unambiguously defined self-energies and vertices. The formula can be a convenient basis for approximate calculations of K lowbar . It also tells us that poles of K lowbar are not shared with (i.e., shifted from) those of the single-particle Green's function, contrary to the conclusion of previous studies.
Malet, F.; Reimann, S. M.; Kristensen, T.; Kavoulakis, G. M.
2011-03-15
We study the rotational properties of a dipolar Bose-Einstein condensate confined in a quasi-two-dimensional anisotropic trap for an arbitrary orientation of the dipoles with respect to their plane of motion. Within the mean-field approximation, we find that the lowest-energy state of the system depends strongly on the relative strength between the dipolar and the contact interactions, as well as on the size and the orientation of the dipoles and the size and the orientation of the deformation of the trapping potential.
Oscillating Solitons in a Three-Component Bose-Einstein Condensate
Szankowski, Piotr; Trippenbach, Marek; Infeld, Eryk; Rowlands, George
2010-09-17
We investigate the properties of three-component Bose-Einstein condensate systems with spin exchange interactions. We consider different coupling constants from those very special ones leading to exact solutions known in the literature. When two solitons collide, a spin component oscillation of the two emerging entities is observed. This behavior seems to be generic. A mathematical model is derived for the emerging solitons. It describes the new oscillatory phenomenon extremely well. Surprisingly, the model is in fact an exact solution to the initial equations. This comes as a bonus.
Dual-species Bose-Einstein condensate of Rb87 and Cs133
NASA Astrophysics Data System (ADS)
McCarron, D. J.; Cho, H. W.; Jenkin, D. L.; Köppinger, M. P.; Cornish, S. L.
2011-07-01
We report the formation of a dual-species Bose-Einstein condensate of Rb87 and Cs133 in the same trapping potential. Our method exploits the efficient sympathetic cooling of Cs133 via elastic collisions with Rb87, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to 2×104 atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the Rb87 during the cooling, we create single-species Cs133 condensates of up to 6×104 atoms.
Creation and counting of defects in a temperature-quenched Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Donadello, S.; Serafini, S.; Bienaimé, T.; Dalfovo, F.; Lamporesi, G.; Ferrari, G.
2016-08-01
We study the spontaneous formation of defects in the order parameter of a trapped ultracold bosonic gas while crossing the critical temperature for Bose-Einstein condensation at different rates. The system has the shape of an elongated ellipsoid, whose transverse width can be varied. For slow enough temperature quenches we find a power-law scaling of the average defect number with the quench rate, as predicted by the Kibble-Zurek mechanism. A breakdown of such a scaling is found for fast quenches, leading to a saturation of the average defect number. We suggest an explanation for this saturation in terms of the mutual interactions among defects.
Dynamics of a Cold Trapped Ion in a Bose-Einstein Condensate
Schmid, Stefan; Haerter, Arne; Denschlag, Johannes Hecker
2010-09-24
We investigate the interaction of a laser-cooled trapped ion (Ba{sup +} or Rb{sup +}) with an optically confined {sup 87}Rb Bose-Einstein condensate. The system features interesting dynamics of the ion and the atom cloud as determined by their collisions and their motion in their respective traps. Elastic as well as inelastic processes are observed and their respective cross sections are determined. We demonstrate that a single ion can be used to probe the density profile of an ultracold atom cloud.
Propagation of collective modes in non-overlapping dipolar Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Gallemi, A.; Guilleumas, M.; Mayol, R.; Pi, M.
2014-04-01
We investigate long-range effects of the dipolar interaction in Bose-Einstein condensates by solving the time-dependent 3D Gross-Pitaevskii equation. We study the propagation of excitations between non-overlapping condensates when a collective mode is excited in one of the condensates. We obtain the frequency shifts due to the long-range character of the dipolar coupling for the bilayer and also the trilayer system when the dipolar mode is excited in one condensate. The propagation of the monopolar and quadrupolar modes are also investigated. The coupled-pendulum model is proposed to qualitatively explain the long range effects of the dipolar coupling.
NASA Astrophysics Data System (ADS)
Ying, Guanwen; Kouzaev, Guennadi
2016-10-01
We present the eigenmodal analysis techniques enhanced towards calculations of optical and non-interacting Bose-Einstein condensate (BEC) modes formed by random potentials and localized by Anderson effect. The results are compared with the published measurements and verified additionally by the convergence criterion. In 2-D BECs captured in circular areas, the randomness shows edge localization of the high-order Tamm-modes. To avoid strong diffusive effect, which is typical for BECs trapped by speckle potentials, a 3-D-lattice potential with increased step magnitudes is proposed, and the BECs in these lattices are simulated and plotted.
Tunable spin-orbit-coupled Bose-Einstein condensates in deep optical lattices
NASA Astrophysics Data System (ADS)
Salerno, M.; Abdullaev, F. Kh.; Gammal, A.; Tomio, Lauro
2016-10-01
Binary mixtures of Bose-Einstein condensates (BECs) trapped in deep optical lattices and subjected to equal contributions of Rashba and Dresselhaus spin-orbit coupling (SOC) are investigated in the presence of a periodic time modulation of the Zeeman field. SOC tunability is explicitly demonstrated by adopting a mean-field tight-binding model for the BEC mixture and by performing an averaging approach in the strong modulation limit. In this case, the system can be reduced to an unmodulated vector discrete nonlinear Schrödinger equation with a rescaled SOC tuning parameter α , which depends only on the ratio between amplitude and frequency of the applied Zeeman field. We consider the attractive interaction case and focus on the effect of the SOC tuning on the localized ground states. The dependence of the spectrum of the linear system on α has been analytically characterized. In particular, we show that extremal curves (ground and highest excited states) of the linear spectrum are continuous piecewise functions (together with their derivatives) of α , which consist of a finite number of decreasing band lobes joined by constant lines. This structure also remains in the presence of inter- and intra-species interactions, the nonlinearity mainly introducing a number of localized states in the band gaps. The stability of ground states in the presence of the modulating field has been demonstrated by real-time evolutions of the original (unaveraged) system. Localization properties of the ground state induced by the SOC tuning, and a parameter design for possible experimental observation, have also been discussed.
Fedichev, Petr O; Fischer, Uwe R
2003-12-12
We propose an experimental scheme to observe the Gibbons-Hawking effect in the acoustic analog of a (1+1)-dimensional de Sitter universe, produced in an expanding, cigar-shaped Bose-Einstein condensate. It is shown that a two-level system created at the center of the trap, an atomic quantum dot interacting with phonons, observes a thermal Bose distribution at the de Sitter temperature.
Fedichev, Petr O; Fischer, Uwe R
2003-12-12
We propose an experimental scheme to observe the Gibbons-Hawking effect in the acoustic analog of a (1+1)-dimensional de Sitter universe, produced in an expanding, cigar-shaped Bose-Einstein condensate. It is shown that a two-level system created at the center of the trap, an atomic quantum dot interacting with phonons, observes a thermal Bose distribution at the de Sitter temperature. PMID:14683099
NASA Astrophysics Data System (ADS)
Salasnich, Luca; Cardoso, Wesley B.; Malomed, Boris A.
2014-09-01
We consider a two-component pancake-shaped, i.e., effectively two-dimensional (2D), Bose-Einstein condensate coupled by the spin-orbit (SO) and Rabi terms. The SO coupling adopted here is of the mixed Rashba-Dresselhaus type. For this configuration, we derive a system of two 2D nonpolynomial Schrödinger equations (NPSEs), for both attractive and repulsive interatomic interactions. In the low- and high-density limits, the system amounts to previously known models, namely, the usual 2D Gross-Pitaevskii equation, or the Schrödinger equation with the nonlinearity of power 7/3. We present simple approximate localized solutions, obtained by treating the SO and Rabi terms as perturbations. Localized solutions of the full NPSE system are obtained in a numerical form. Remarkably, in the case of the attractive nonlinearity acting in free space (i.e., without any 2D trapping potential), we find parameter regions where the SO and Rabi couplings make 2D fundamental solitons dynamically stable.
Thermal spin fluctuations in spinor Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Melé-Messeguer, M.; Juliá-Díaz, B.; Polls, A.; Santos, L.
2013-03-01
We study the thermal activation of spin fluctuations in dynamically stable spinor Bose-Einstein condensates. We analyze the specific cases of a nondipolar spin-1 condensate in the state m=0, where thermal activation results from spin-changing collisions, and of a chromium condensate in the maximally stretched state m=-3, where thermal spin fluctuations are due to dipole-induced spin relaxation. In both cases, we show that the low energy associated to the spinor physics may be employed for thermometry purposes down to extremely low temperatures, typically impossible to measure in Bose-Einstein condensates with the usual thermometric techniques. Moreover, the peculiar dependence of the system's entropy with the applied Zeeman energy opens a possible route for adiabatic cooling.
Breakdown of Bose-Einstein Distribution in Photonic Crystals
Lo, Ping-Yuan; Xiong, Heng-Na; Zhang, Wei-Min
2015-01-01
In the last two decades, considerable advances have been made in the investigation of nano-photonics in photonic crystals. Previous theoretical investigations of photon dynamics were carried out at zero temperature. Here, we investigate micro/nano cavity photonics in photonic crystals at finite temperature. Due to photonic-band-gap-induced localized long-lived photon dynamics, we discover that cavity photons in photonic crystals do not obey Bose-Einstein statistical distribution. Within the photonic band gap and in the vicinity of the band edge, cavity photons combine the long-lived non-Markovain dynamics with thermal fluctuations together to form photon states that memorize the initial cavity state information. As a result, Bose-Einstein distribution is completely broken down in these regimes, even if the thermal energy is larger or much larger than the cavity detuning energy. In this investigation, a crossover phenomenon from equilibrium to nonequilibrium steady states is also revealed. PMID:25822135
Breakdown of Bose-Einstein distribution in photonic crystals.
Lo, Ping-Yuan; Xiong, Heng-Na; Zhang, Wei-Min
2015-01-01
In the last two decades, considerable advances have been made in the investigation of nano-photonics in photonic crystals. Previous theoretical investigations of photon dynamics were carried out at zero temperature. Here, we investigate micro/nano cavity photonics in photonic crystals at finite temperature. Due to photonic-band-gap-induced localized long-lived photon dynamics, we discover that cavity photons in photonic crystals do not obey Bose-Einstein statistical distribution. Within the photonic band gap and in the vicinity of the band edge, cavity photons combine the long-lived non-Markovain dynamics with thermal fluctuations together to form photon states that memorize the initial cavity state information. As a result, Bose-Einstein distribution is completely broken down in these regimes, even if the thermal energy is larger or much larger than the cavity detuning energy. In this investigation, a crossover phenomenon from equilibrium to nonequilibrium steady states is also revealed.
Entanglement entropy and mutual information in Bose-Einstein condensates
Ding Wenxin; Yang Kun
2009-07-15
In this paper we study the entanglement properties of free nonrelativistic Bose gases. At zero temperature, we calculate the bipartite block entanglement entropy of the system and find that it diverges logarithmically with the particle number in the subsystem. For finite temperatures, we study the mutual information between the two blocks. We first analytically study an infinite-range hopping model, then numerically study a set of long-range hopping models in one dimension that exhibit Bose-Einstein condensation. In both cases we find that a Bose-Einstein condensate, if present, makes a divergent contribution to the mutual information which is proportional to the logarithm of the number of particles in the condensate in the subsystem. The prefactor of the logarithmic divergent term is model dependent.
Theory of cold atoms: Bose-Einstein statistics
NASA Astrophysics Data System (ADS)
Yukalov, V. I.
2016-06-01
This tutorial is the continuation of the previous tutorial part, published in (2013 Laser Phys. 23 062001), where the basic mathematical techniques required for an accurate description of cold atoms for both types of quantum statistics are expounded. In the present part, the specifics of the correct theoretical description of atoms obeying Bose-Einstein statistics are explained, including trapped Bose atoms. In the theory of systems exhibiting the phenomenon of Bose-Einstein condensation, there exists a number of delicate mathematical points, whose misunderstanding often results in principally wrong conclusions. This is why the consideration in the present tutorial is sufficiently detailed in order that the reader could clearly understand the underlying mathematics and would avoid confusions.
Interferometry with Bose-Einstein condensates in microgravity.
Müntinga, H; Ahlers, H; Krutzik, M; Wenzlawski, A; Arnold, S; Becker, D; Bongs, K; Dittus, H; Duncker, H; Gaaloul, N; Gherasim, C; Giese, E; Grzeschik, C; Hänsch, T W; Hellmig, O; Herr, W; Herrmann, S; Kajari, E; Kleinert, S; Lämmerzahl, C; Lewoczko-Adamczyk, W; Malcolm, J; Meyer, N; Nolte, R; Peters, A; Popp, M; Reichel, J; Roura, A; Rudolph, J; Schiemangk, M; Schneider, M; Seidel, S T; Sengstock, K; Tamma, V; Valenzuela, T; Vogel, A; Walser, R; Wendrich, T; Windpassinger, P; Zeller, W; van Zoest, T; Ertmer, W; Schleich, W P; Rasel, E M
2013-03-01
Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity. PMID:23496709
Tunnelling of spin-orbit coupled Bose-Einstein condensates in driven double-well potential
NASA Astrophysics Data System (ADS)
Niu, Zhen-Xia; Zhang, Ai-Xia; Xue, Ju-Kui
2016-08-01
The tunnelling dynamics of spin-orbit (SO) coupled Bose-Einstein condensates in a periodically driven double-well potential are investigated both theoretically and numerically. We find that, when the SO coupling is absent, the atomic interactions suppress the tunnelling (as in usual Bose-Einstein condensed system), and the Zeeman field does not influence the usual tunnelling. When the SO coupling is present, the coupling of the atomic interactions and the Zeeman-field intensity can either enhance or suppress the tunnelling. The system undergoes rich transformations from the coherent tunnelling (CT) to the coherent destruction of tunnelling (CDT) when the SO coupling or the atomic interactions or the Zeeman-field intensity changes. In high-frequency region, the triangular structure and the circle structure are revealed in quasi-energy bands of the system, the width of the triangular structure or the circle structure and the localization width are relevant. And the SO coupling modifies traditional degenerate modes of quasi-energy bands. The results provide a possible way to control the usual tunnelling and the spin-flipping tunnelling in double-well potential.
Theory for Bose-Einstein condensation of light in nanofabricated semiconductor microcavities
NASA Astrophysics Data System (ADS)
de Leeuw, A.-W.; van der Wurff, E. C. I.; Duine, R. A.; van Oosten, D.; Stoof, H. T. C.
2016-07-01
We construct a theory for Bose-Einstein condensation of light in nanofabricated semiconductor microcavities. We model the semiconductor by one conduction and one valence band which consist of electrons and holes that interact via a Coulomb interaction. Moreover, we incorporate screening effects by using a contact interaction with the scattering length for a Yukawa potential and describe in this manner the crossover from exciton gas to electron-hole plasma as we increase the excitation level of the semiconductor. We then show that the dynamics of the light in the microcavities is damped due to the coupling to the semiconductor. Furthermore, we demonstrate that on the electron-hole plasma side of the crossover, which is relevant for the Bose-Einstein condensation of light, this damping can be described by a single dimensionless damping parameter that depends on the external pumping. Hereafter, we propose to probe the superfluidity of light in these nanofabricated semiconductor microcavities by making use of the differences in the response in the normal or superfluid phase to a sudden rotation of the trap. In particular, we determine frequencies and damping of the scissors modes that are excited in this manner. Moreover, we show that a distinct signature of the dynamical Casimir effect can be observed in the density-density correlations of the excited light fluid.
Bloch oscillations of Bose-Einstein condensates: breakdown and revival.
Witthaut, D; Werder, M; Mossmann, S; Korsch, H J
2005-03-01
We investigate the dynamics of Bose-Einstein condensates in a tilted one-dimensional periodic lattice within the mean-field (Gross-Pitaevskii) description. Unlike in the linear case the Bloch oscillations decay because of nonlinear dephasing. Pronounced revival phenomena are observed. These are analyzed in detail in terms of a simple integrable model constructed by an expansion in Wannier-Stark resonance states. We also briefly discuss the pulsed output of such systems for stronger static fields.
Texture Control in a Pseudospin Bose-Einstein Condensate
Ruben, Gary; Morgan, Michael J.; Paganin, David M.
2010-11-26
We describe a wave function engineering approach to the formation of textures in nonrotated multicomponent Bose-Einstein condensates. With numerical simulations of a viable two-component condensate experiment, we demonstrate the formation of a ballistically expanding regular lattice texture, composed of half-quantum vortices and spin-2 textures. The formation is described by a linear interference process in which the geometry and phase of three initially separated wave packets provide deterministic control over the resulting lattice texture.
Beyond Spontaneously Broken Symmetry in Bose-Einstein Condensates
Mullin, W. J.; Laloee, F.
2010-04-16
Spontaneous symmetry breaking (SSB) for Bose-Einstein condensates cannot treat phase off-diagonal effects, and thus cannot explain Bell inequality violations. We describe another situation that is beyond a SSB treatment: an experiment where particles from two (possibly macroscopic) condensate sources are used for conjugate measurements of the relative phase and populations. Off-diagonal phase effects are characterized by a 'quantum angle' and observed via 'population oscillations', signaling quantum interference of macroscopically distinct states.
Magnons as a Bose-Einstein Condensate in Nanocrystalline Gadolinium
Kaul, S. N.; Mathew, S. P.
2011-06-17
The recent observation [S. P. Mathew et al., J. Phys. Conf. Ser. 200, 072047 (2010)] of the anomalous softening of spin-wave modes at low temperatures in nanocrystalline gadolinium is interpreted as a Bose-Einstein condensation (BEC) of magnons. A self-consistent calculation, based on the BEC picture, is shown to closely reproduce the observed temperature variations of magnetization and specific heat at constant magnetic fields.
Taming rogue waves in vector Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Vinayagam, P. S.; Radha, R.; Porsezian, K.
2013-10-01
Using gauge transformation method, we generate rogue waves for the two-component Bose-Einstein condensates (BECs) governed by the symmetric coupled Gross-Pitaevskii (GP) equations and study their dynamics. We also suggest a mechanism to tame the rogue waves either by manipulating the scattering length through Feshbach resonance or the trapping frequency, a phenomenon not witnessed in the domain of BECs, and we believe that these results may have wider ramifications in the management of rogons.
Controlling chaos in the Bose-Einstein condensate
Cong Fuzhong Wang Zhixia; Hua Hongtu; Pang Shichun; Tong Shouyu
2012-03-15
The spatial structure of the Bose-Einstein condensate (BEC) is investigated and spatially chaotic distributions of the condensates are revealed. By means of changing the s-wave scattering length with a Feshbach resonance, the chaotic behavior can be well controlled to enter into periodicity. Numerical simulation shows that there are different periodic orbits according to different s-wave scattering lengths only if the Lyapunov exponent of the system is negative.
Bose-Einstein condensation on a microelectronic chip.
Hänsel, W; Hommelhoff, P; Hänsch, T W; Reichel, J
2001-10-01
Although Bose-Einstein condensates of ultracold atoms have been experimentally realizable for several years, their formation and manipulation still impose considerable technical challenges. An all-optical technique that enables faster production of Bose-Einstein condensates was recently reported. Here we demonstrate that the formation of a condensate can be greatly simplified using a microscopic magnetic trap on a chip. We achieve Bose-Einstein condensation inside the single vapour cell of a magneto-optical trap in as little as 700 ms-more than a factor of ten faster than typical experiments, and a factor of three faster than the all-optical technique. A coherent matter wave is emitted normal to the chip surface when the trapped atoms are released into free fall; alternatively, we couple the condensate into an 'atomic conveyor belt', which is used to transport the condensed cloud non-destructively over a macroscopic distance parallel to the chip surface. The possibility of manipulating laser-like coherent matter waves with such an integrated atom-optical system holds promise for applications in interferometry, holography, microscopy, atom lithography and quantum information processing.
Bose-Einstein condensation on a microelectronic chip
NASA Astrophysics Data System (ADS)
Hänsel, W.; Hommelhoff, P.; Hänsch, T. W.; Reichel, J.
2001-10-01
Although Bose-Einstein condensates of ultracold atoms have been experimentally realizable for several years, their formation and manipulation still impose considerable technical challenges. An all-optical technique that enables faster production of Bose-Einstein condensates was recently reported. Here we demonstrate that the formation of a condensate can be greatly simplified using a microscopic magnetic trap on a chip. We achieve Bose-Einstein condensation inside the single vapour cell of a magneto-optical trap in as little as 700ms-more than a factor of ten faster than typical experiments, and a factor of three faster than the all-optical technique. A coherent matter wave is emitted normal to the chip surface when the trapped atoms are released into free fall; alternatively, we couple the condensate into an `atomic conveyor belt', which is used to transport the condensed cloud non-destructively over a macroscopic distance parallel to the chip surface. The possibility of manipulating laser-like coherent matter waves with such an integrated atom-optical system holds promise for applications in interferometry, holography, microscopy, atom lithography and quantum information processing.
NASA Astrophysics Data System (ADS)
Tacla, Alexandre B.; Caves, Carlton M.
2013-02-01
We study the mean-field dynamics and the reduced-dimension character of two-mode Bose-Einstein condensates (BECs) in highly anisotropic traps. By means of perturbative techniques, we show that the tightly confined (transverse) degrees of freedom can be decoupled from the dynamical equations at the expense of introducing additional effective three-body, attractive, intra- and inter-mode interactions into the dynamics of the loosely confined (longitudinal) degrees of freedom. These effective interactions are mediated by changes in the transverse wave function. The perturbation theory is valid as long as the nonlinear scattering energy is small compared to the transverse energy scales. This approach leads to reduced-dimension mean-field equations that optimally describe the evolution of a two-mode condensate in general quasi-one-dimensional (1D) and quasi-two-dimensional geometries. We use this model to investigate the relative phase and density dynamics of a two-mode, cigar-shaped 87Rb BEC. We study the relative-phase dynamics in the context of a nonlinear Ramsey interferometry scheme, which has recently been proposed as a novel platform for high-precision interferometry. Numerical integration of the coupled, time-dependent, three-dimensional, two-mode Gross-Pitaevskii equations for various atom numbers shows that this model gives a considerably more refined analytical account of the mean-field evolution than an idealized quasi-1D description.
NASA Astrophysics Data System (ADS)
Wang, Deng-Shan; Han, Wei; Shi, Yuren; Li, Zaidong; Liu, Wu-Ming
2016-07-01
The spin-1 Bose-Einstein condensates trapped in a standing light wave can be described by three coupled Gross-Pitaevskii equations with a periodic potential. In this paper, nine families of stationary solutions without phase structures in the form of Jacobi elliptic functions are proposed, and their stabilities are analyzed by both linear stability analysis and dynamical evolutions. Taking the ferromagnetic 87Rb atoms and antiferromagnetic (polar) 23Na atoms as examples, we investigate the stability regions of the nine stationary solutions, which are given in term of elliptic modulus k. It is shown that for the same stationary solution the stability regions of condensates with antiferromagnetic (polar) spin-dependent interactions are larger than that of the condensates with ferromagnetic ones. The dn-dn-dn stationary solution is the most stable solution among the nine families of stationary solutions. Moreover, in the same standing light wave, the spin-1 Bose-Einstein condensates are more stable than the scalar Bose-Einstein condensate.
Stirring a ring Bose-Einstein condensate: vortices and overall circulation
NASA Astrophysics Data System (ADS)
Murray, Noel; Edwards, Mark; Clark, Charles W.
2013-03-01
We have studied the process whereby stirring a superfluid Bose-Einstein condensate confined in a ring-shaped potential leads to an overall circulation. We solved the time-dependent Gross-Pitaevskii equation under conditions chosen to match those of an experiment recently conducted at NIST. Briefly, 500,000 Na atoms where confined at the ring-shaped intersection of a red-detuned horizontal light sheet and a vertically propagating Laguerre-Gauss beam. Stirring was carried via a blue-detuned gaussian beam. We found that, at first, the stirring spawned a number of vortex-antivortex pairs and then stopped. These vortices displayed a complicated dynamical behavior which slowly reduced the number of vortices pairwise via annihilation and singly via diffusion into surface modes of the condensate. At the end of this dynamics, the set of vortices was replaced by an overall circulation of atoms around the ring. We present examples of this behavior, give a simple model of vortex motion and vortex-vortex interaction, and show how the production and annihilation of vortices gets turned into a overall circulation of the ring Bose-Einstein condensate. Support in part by NSF grant #1068761.
Stirring a ring Bose-Einstein condensate: vortices and overall circulation
NASA Astrophysics Data System (ADS)
Murray, Noel; Edwards, Mark; Clark, Charles
2013-05-01
We have studied the process whereby stirring a superfluid Bose-Einstein condensate confined in a ring-shaped potential leads to an overall circulation. We solved the time-dependent Gross-Pitaevskii equation under conditions chosen to match those of an experiment recently conducted at NIST. Briefly, 500,000 Na atoms where confined at the ring-shaped intersection of a red-detuned horizontal light sheet and a vertically propagating Laguerre-Gauss beam. Stirring was carried via a blue-detuned gaussian beam. We found that, at first, the stirring spawned a number of vortex-antivortex pairs and then stopped. These vortices displayed a complicated dynamical behavior which slowly reduced the number of vortices pairwise via annihilation and singly via diffusion into surface modes of the condensate. At the end of this dynamics, the set of vortices was replaced by an overall circulation of atoms around the ring. We present examples of this behavior, give a simple model of vortex motion and vortex-vortex interaction, and show how the production and annihilation of vortices gets turned into a overall circulation of the ring Bose-Einstein condensate. Support in part by NSF grant #1068761.
Quench dynamics of a Bose-Einstein condensate under synthetic spin-orbit coupling
NASA Astrophysics Data System (ADS)
Deng, Tian-Shu; Zhang, Wei; Yi, Wei; Guo, Guang-Can
2016-05-01
We study the quench dynamics of a Bose-Einstein condensate under a Raman-assisted synthetic spin-orbit coupling. To model the dynamical process, we adopt a self-consistent Bogoliubov approach, which is equivalent to applying the time-dependent Bogoliubov-de Gennes equations. We investigate the dynamics of the condensate fraction as well as the momentum distribution of the Bose gas following a sudden change of system parameters. Typically, the system evolves into a steady state in the long-time limit, which features an oscillating momentum distribution and a stationary condensate fraction. We investigate how different quench parameters such as the inter- and intraspecies interactions and the spin-orbit-coupling parameters affect the condensate fraction in the steady state. Furthermore, we find that the time average of the oscillatory momentum distribution in the long-time limit can be described by a generalized Gibbs ensemble with two branches of momentum-dependent Gibbs temperatures. Our study is relevant to the experimental investigation of dynamical processes in a spin-orbit-coupled Bose-Einstein condensate.
Bose-Einstein condensation of spin wave quanta at room temperature.
Dzyapko, O; Demidov, V E; Melkov, G A; Demokritov, S O
2011-09-28
Spin waves are delocalized excitations of magnetic media that mainly determine their magnetic dynamics and thermodynamics at temperatures far below the critical one. The quantum-mechanical counterparts of spin waves are magnons, which can be considered as a gas of weakly interacting bosonic quasi-particles. Here, we discuss the room-temperature kinetics and thermodynamics of the magnon gas in yttrium iron garnet films driven by parametric microwave pumping. We show that for high enough pumping powers, the thermalization of the driven gas results in a quasi-equilibrium state described by Bose-Einstein statistics with a non-zero chemical potential. Further increases of the pumping power cause a Bose-Einstein condensation documented by an observation of the magnon accumulation at the lowest energy level. Using the sensitivity of the Brillouin light scattering spectroscopy to the degree of coherence of the scattering magnons, we confirm the spontaneous emergence of coherence of the magnons accumulated at the bottom of the spectrum, occurring if their density exceeds a critical value.
Engineered potentials in ultracold Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Campbell, Daniel L.
Bose-Einstein condensates (BECs) are a recent addition to the portfolio of quantum materials some of which have profound commercial and military applications e.g., superconductors, superfluids and light emitting diodes. BECs exist in the lowest motional modes of a trap and have the lowest temperatures achieved by mankind. With full control over the shape of the trap the experimentalist may explore an extremely diverse set of Hamiltonians which may be altered mid-experiment. These properties are particularly suited for realizing novel quantum systems. This thesis explores interaction-driven domain formation and the subsequent domain coarsening for two immiscible BEC components. Because quantum coherences associated with interactions in BECs can be derived from low energy scattering theory we compare our experimental results to both a careful simulation (performed by Brandon Anderson) and an analytical prediction. This result very carefully explores the question of how a metastable system relaxes at the extreme limit of low temperature. We also explore spin-orbit coupling (SOC) of a BEC which links the linear and discrete momentum transferable by two counterpropagating ''Raman'' lasers that resonantly couple the ground electronic states of our BECs. SOC is used similarly in condensed matter systems to describe coupling between charge carrier spin and crystal momentum and is a necessary component of the quantum spin Hall effect and topological insulators. SOC links the linear and discrete momentum transferable by two counterpropagating ''Raman'' lasers and a subset of the ground electronic states of our BEC. The phases of an effective 2-spin component spin-orbit coupling (SOC) in a spin-1 BEC are described in Lin et al. (2011). We measure the phase transition between two phases of a spin-1 BEC with SOC which cannot be mimicked by a spin-1/2 system. The order parameter that describes transitions between these two phases is insensitive to magnetic field fluctuations. I
Wu Lei; Zhang Jiefang; Li Lu; Mihalache, Dumitru; Malomed, Boris A.; Liu, W. M.
2010-06-15
We construct exact solutions of the Gross-Pitaevskii equation for solitary vortices, and approximate ones for fundamental solitons, in two-dimensional models of Bose-Einstein condensates with a spatially modulated nonlinearity of either sign and a harmonic trapping potential. The number of vortex-soliton (VS) modes is determined by the discrete energy spectrum of a related linear Schroedinger equation. The VS families in the system with the attractive and repulsive nonlinearity are mutually complementary. Stable VSs with vorticity S{>=}2 and those corresponding to higher-order radial states are reported, in the case of the attraction and repulsion, respectively.
NASA Astrophysics Data System (ADS)
Stamper-Kurn, Dan M.
2000-12-01
Bose-Einstein condensates of a dilute atomic gas were explored as a testbed for theories of the weakly interacting Bose gas, as a source of coherent matter waves, and as a new quantum fluid. A dc magnetic trap, various optical probing and manipulation techniques and an optical trap were developed for this work. The density and momentum distributions and the interaction energies of ultra-cold Bose gases were measured and found to agree with mean-field theory. The reduction of the condensate fraction due to interactions was observed using a trapping potential created by magnetic and optical forces. The formation of a Bose-Einstein condensate in a super- cooled Bose gas was time resolved, and showed evidence for bosonic stimulation. The reversible formation of a Bose-Einstein condensate through an adiabatic change in the trapping potential was predicted and demonstrated. Excitations in a Bose gas were studied in various regimes. The speed of Bogoliubov sound was measured as a function of condensate density. The frequency and damping rates of collective excitations of both the condensate and the non-condensed cloud were measured over a wide temperature range, providing a critical test of mean- field theory and challenging finite-temperature descriptions. The onset of hydrodynamic oscillations was observed. The dynamic structure factor of a Bose-Einstein condensate was measured by stimulated light scattering. Excitations in the free-particle and phonon regime were accessed, allowing for a measurement of the coherence length, a spectroscopic determination of the excitation spectrum, and the observation of suppressed small-angle light scattering. The development of an all-optical trap for Bose-Einstein condensates led to the creation of spinor condensates, which are described by a vectorial order parameter. Ground-state spin structures were studied and a spin- domain diagram for their description was developed. Metastable Bose condensates were observed, caused by energy
Bose-Einstein-condensate interferometer with macroscopic arm separation
NASA Astrophysics Data System (ADS)
Garcia-Salazar, Ofir
The basis of our study was to implement an atom interferometer using 87Rb Bose Einstein condensates which has advantages in sensitivity over current interferometers that use cold atoms and light. Interferometers are devices which can accurately measure phase differences between waves that interfere and originate from a coherent source (or sources). We developed a weakly confining waveguide having o x ≈ 3 Hz, oz ≈ 3 Hz, o y ≈ 1 Hz as characteristic oscillation frequencies. Weak confinement, specially along the "y" direction, means the condensate can displace along this axis and interaction energies of the atoms in the condensate are reduced [43]. We have been able to successfully demonstrate condensate interference in our waveguide using a Mach Zehnder configuration. Coherence times of up to 40 ms have been observed, and the maximum center to center separation of the condensates recorded was of 240 mum. At this separation length, the two clouds corresponding to each of the interferometer's arms are completely separated. To our knowledge, this is the first time a picture has been taken of two groups of atoms separated by a macroscopic distance while in a quantum superposition of being in either cloud. The coherence time and length measurements presented in our work have been among the longest ones achieved so far for interferometry using condensed atoms. Interference visibility of 60% was observed up to 40 ms. We believe technical limitations in the techniques used to manipulate the atoms are responsible for the sudden drop in visibility at 44 ms. For example, unwanted laser reflections and interference patterns in our chamber affect the techniques used to split and reflect the atoms. However, we see coherence up to 80 ms from shot to shot, suggesting we could dramatically improve coherence times. Because of the weak confinement of our trap, we expect to improve coherence times up to an order of magnitude before running into phase diffusion effects [27]. It is
Coherence and Squeezing of Bose-Einstein Condensates in Double Wells
NASA Astrophysics Data System (ADS)
Yi, Xiao-jie
2016-05-01
We investigate coherence and squeezing of a two-mode Bose-Einstein condensate trapped in a double-well potential. By analytically deriving the form of coherence and numerically calculating the squeezing parameter, we show that the coherence and the squeezing may be controlled by adjusting some parameters of the two-mode Bose-Einstein condensate.
Growth dynamics of a Bose-Einstein condensate in a dimple trap without cooling
Garrett, Michael C.; Davis, Matthew J.; Ratnapala, Adrian; Ooijen, Eikbert D. van; Vale, Christopher J.; Weegink, Kristian; Schnelle, Sebastian K.; Vainio, Otto; Heckenberg, Norman R.; Rubinsztein-Dunlop, Halina
2011-01-15
We study the formation of a Bose-Einstein condensate in a cigar-shaped three-dimensional harmonic trap, induced by the controlled addition of an attractive ''dimple'' potential along the weak axis. In this manner we are able to induce condensation without cooling due to a localized increase in the phase-space density. We perform a quantitative analysis of the thermodynamic transformation in both the sudden and adiabatic regimes for a range of dimple widths and depths. We find good agreement with equilibrium calculations based on self-consistent semiclassical Hartree-Fock theory describing the condensate and thermal cloud. We observe that there is an optimal dimple depth that results in a maximum in the condensate fraction. We also study the nonequilibrium dynamics of condensate formation in the sudden turn-on regime, finding good agreement for the observed time dependence of the condensate fraction with calculations based on quantum kinetic theory.
Dynamical spin-density waves in a spin-orbit-coupled Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Li, Yan; Qu, Chunlei; Zhang, Yongsheng; Zhang, Chuanwei
2015-07-01
Synthetic spin-orbit (SO) coupling, an important ingredient for quantum simulation of many exotic condensed matter physics, has recently attracted considerable attention. The static and dynamic properties of a SO-coupled Bose-Einstein condensate (BEC) have been extensively studied in both theory and experiment. Here we numerically investigate the generation and propagation of a dynamical spin-density wave (SDW) in a SO-coupled BEC using a fast moving Gaussian-shaped barrier. We find that the SDW wavelength is sensitive to the barrier's velocity while varies slightly with the barrier's peak potential or width. We qualitatively explain the generation of SDW by considering a rectangular barrier in a one-dimensional system. Our results may motivate future experimental and theoretical investigations of rich dynamics in the SO-coupled BEC induced by a moving barrier.
NASA Astrophysics Data System (ADS)
Alcala, Diego; Glick, Joseph; Carr, Lincoln D.
2015-05-01
The quantum escape problem is famous in the context of quasi-bound states and chemical and nuclear reactions. We address three outstanding questions in this form of quantum tunneling. (1) How are tunneling rates modified by many-body effects, in particular beyond the mean field? (2) What is the role of higher order quantum effects like entanglement and correlations? (3) What is the dynamics of the escape process? To this end we study both repulsive and attractive Bose-Einstein condensates via matrix-product state methods for entangled dynamics. We find that entanglement is maximized when about half the particles have escaped. We find preliminary evidence that the time derivative of number fluctuations serves as an entanglement witness. Funded by NSF.
Vector solitons in nearly one-dimensional Bose-Einstein condensates
Salasnich, Luca; Malomed, Boris A.
2006-11-15
We derive a system of nonpolynomial Schroedinger equations for one-dimensional wave functions of two components in a binary self-attractive Bose-Einstein condensate loaded in a cigar-shaped trap. The system is obtained by means of the variational approximation, starting from the coupled three-dimensional (3D) Gross-Pitaevskii equations and assuming, as usual, the factorization of 3D wave functions. The system can be obtained in a tractable form under a natural condition of symmetry between the two species. A family of vector (two-component) soliton solutions is constructed. Collisions between orthogonal solitons (ones belonging to the different components) are investigated by means of simulations. The collisions are essentially inelastic. They result in strong excitation of intrinsic vibrations in the solitons, and create a small orthogonal component ('shadow') in each colliding soliton. The collision may initiate collapse, which depends on the mass and velocities of the solitons.
Renormalization group analysis of ultracold Fermi gases with two-body attractive interaction
NASA Astrophysics Data System (ADS)
Guo, Xiaoyong; Chi, Zimeng; Zheng, Qiang; Wang, Zaijun
2016-01-01
We propose a new functional renormalization group (RG) strategy to investigate the many-body physics of interacting ultracold Fermi gases. By mapping the Ginzburg-Landau (GL) action of Fermi gases onto a complex φ4-model, we can obtain the closed flow equation in the one-loop approximation. An analysis of the emerging RG flow gives the ground state behavior. The Hamiltonian of a Fermi gas with a two-body attractive interaction is used as a demonstration to clarify our treatment. The fixed point structure reveals not only the condensation phase transition, but also the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensation (BEC) crossover. The effect of the imaginary time renormalization is also discussed. It is shown that for the dynamical field configuration our RG procedure can reproduce the well known theoretical results of BCS-BEC crossover, while under a static approximation the phase transition takes place at a higher critical temperature.
Vortex formation during the growth of Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Weiler, Chad; Neely, Tyler; Scherer, David; Anderson, Brian
2007-06-01
We experimentally study of the growth of Bose-Einstein condensates in harmonic trapping potentials with laser-induced perturbations to the potential well. We find that some time- independent perturbations can significantly impact the growth process and final state of the BEC. In particular, in numerical simulations and our experiments, we have observed the generation of vortices and vortex-antivortex pairs as a result of creating BECs in perturbed potentials. We will describe the results of our ongoing and completed experiments (D.R. Scherer, C.N. Weiler, T.W. Neely, B.P. Anderson, cond-mat/0610187, to be published in Phys. Rev. Lett.).
Hysteresis effects in rotating Bose-Einstein condensates
Jackson, B.; Barenghi, C. F.
2006-10-15
We study the formation of vortices in a dilute Bose-Einstein condensate confined in a rotating anisotropic trap. We find that the number of vortices and angular momentum attained by the condensate depend upon the rotation history of the trap and on the number of vortices present in the condensate initially. A simplified model based on hydrodynamic equations is developed, and used to explain this effect in terms of a shift in the resonance frequency of the quadrupole mode of the condensate in the presence of a vortex lattice. Differences between the spin-up and spin-down response of the condensate are found, demonstrating hysteresis phenomena in this system.
Bose-Einstein Condensation of Dark Matter Axions
Sikivie, P.; Yang, Q.
2009-09-11
We show that cold dark matter axions thermalize and form a Bose-Einstein condensate (BEC). We obtain the axion state in a homogeneous and isotropic universe, and derive the equations governing small axion perturbations. Because they form a BEC, axions differ from ordinary cold dark matter in the nonlinear regime of structure formation and upon entering the horizon. Axion BEC provides a mechanism for the production of net overall rotation in dark matter halos, and for the alignment of cosmic microwave anisotropy multipoles.
Bose-Einstein condensation of dark matter axions.
Sikivie, P; Yang, Q
2009-09-11
We show that cold dark matter axions thermalize and form a Bose-Einstein condensate (BEC). We obtain the axion state in a homogeneous and isotropic universe, and derive the equations governing small axion perturbations. Because they form a BEC, axions differ from ordinary cold dark matter in the nonlinear regime of structure formation and upon entering the horizon. Axion BEC provides a mechanism for the production of net overall rotation in dark matter halos, and for the alignment of cosmic microwave anisotropy multipoles.
Geometrical Pumping with a Bose-Einstein Condensate.
Lu, H-I; Schemmer, M; Aycock, L M; Genkina, D; Sugawa, S; Spielman, I B
2016-05-20
We realized a quantum geometric "charge" pump for a Bose-Einstein condensate (BEC) in the lowest Bloch band of a novel bipartite magnetic lattice. Topological charge pumps in filled bands yield quantized pumping set by the global-topological-properties of the bands. In contrast, our geometric charge pump for a BEC occupying just a single crystal momentum state exhibits nonquantized charge pumping set by local-geometrical-properties of the band structure. Like topological charge pumps, for each pump cycle we observed an overall displacement (here, not quantized) and a temporal modulation of the atomic wave packet's position in each unit cell, i.e., the polarization. PMID:27258857
Three-vortex configurations in trapped Bose-Einstein condensates
Seman, J. A.; Henn, E. A. L.; Shiozaki, R. F.; Ramos, E. R. F.; Caracanhas, M.; Castilho, P.; Castelo Branco, C.; Tavares, P. E. S.; Poveda-Cuevas, F. J.; Magalhaes, K. M. F.; Bagnato, V. S.; Haque, M.; Roati, G.
2010-09-15
We report on the creation of three-vortex clusters in a {sup 87}Rb Bose-Einstein condensate by oscillatory excitation of the condensate. This procedure can create vortices of both circulations, so that we are able to create several types of vortex clusters using the same mechanism. The three-vortex configurations are dominated by two types, namely, an equilateral-triangle arrangement and a linear arrangement. We interpret these most stable configurations respectively as three vortices with the same circulation and as a vortex-antivortex-vortex cluster. The linear configurations are very likely experimental signatures of predicted stationary vortex clusters.
Texture control in a pseudospin Bose-Einstein condensate.
Ruben, Gary; Morgan, Michael J; Paganin, David M
2010-11-26
We describe a wave function engineering approach to the formation of textures in nonrotated multicomponent Bose-Einstein condensates. With numerical simulations of a viable two-component condensate experiment, we demonstrate the formation of a ballistically expanding regular lattice texture, composed of half-quantum vortices and spin-2 textures. The formation is described by a linear interference process in which the geometry and phase of three initially separated wave packets provide deterministic control over the resulting lattice texture.
Excitation spectrum of Bose-Einstein Condensates with modified dispersion
NASA Astrophysics Data System (ADS)
Mossman, Maren; Khamehchi, M. A.; Engels, Peter
2015-05-01
Bose-Einstein Condensates provide a flexible platform to model a wide variety of condensed matter phenomena. To this goal, Raman dressing schemes and dynamical lattices have emerged as a premier tool, allowing for a modification of the dispersion relation leading to spin-orbit coupling and artificial gauge fields. Using Bragg spectroscopy, we investigate the collective excitation spectrum of BECs with engineered dispersion relations and study consequences of a roton-like minimum that can be softened by changing Raman dressing parameters. We report on the current status and future directions of our experiments. This work is supported by NSF.
Winding up superfluid in a torus via Bose Einstein condensation
Das, Arnab; Sabbatini, Jacopo; Zurek, Wojciech H
2010-12-16
We simulate Bose-Einstein condensation at finite temperature in a ring employing stochastic Gross-Pitaevskii equation and show that cooling through the critical point can generate topologically stable quantized circulation of the newborn condensate around the ring. The resulting winding numbers exhibiting Gaussian distribution with dispersion following scaling behavior predicted by the Kibble-Zurek mechanism (KZM). This opens up possibilities for direct experimental study of the underlying phase transition and the basic principles of KZM extended to account for such circulations. We discuss the effect of inhomogeneity on the above phenomenon by considering the effect of tilting of the ring in the gravitational field.
Wave-function monopoles in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Busch, Th.; Anglin, J. R.
1999-10-01
Experimental preparation of multispecies Bose-Einstein condensates should permit the creation of topologically stable defects beyond the superfluid vortex. But the coldness and isolation of condensates should also permit the survival for observable durations of ``pseudodefects,'' such as the one-dimensional dark soliton: localized structures related to a defect but not topologically stable. In this paper we investigate the viability of pseudodefects beyond one dimension, by examining ``wave-function monopoles'' in two-species condensates in two dimensions. We identify interesting instabilities, including a ``dancing mode'' for monopoles of higher winding number, and (in a one-dimensional limit) ``superfluid roulette.''
Composite nature of hadrons and Bose-Einstein correlations
NASA Astrophysics Data System (ADS)
Bialas, A.
2016-07-01
I am reporting results of two papers, written together with W.Florkowski and K.Zalewski [1, 2], discussing the consequences of the observation [3] that, due to their composite nature and thus finite size, hadrons observed in the HBT measurements must be correlated in space-time. Using the blast-wave model [4] adjusted [1] to ALICE data on the measured HBT radii in pp collisions at 7 TeV [5], the full Bose-Einstein correlation functions in three direction (out, side, long) are evaluated. The results are presented together with some additional comments.
Early stage of superradiance from Bose-Einstein condensates
Buchmann, L. F.; Lambropoulos, P.; Nikolopoulos, G. M.; Zobay, O.
2010-08-15
We investigate the dynamics of matter and optical waves at the early stage of superradiant Rayleigh scattering from Bose-Einstein condensates. Our analysis is within a spatially dependent quantum model which is capable of providing analytic solutions for the operators of interest. The predictions of the present model are compared to the predictions of a closely related mean-field model, and we provide a procedure that allows one to calculate quantum expectation values by averaging over semiclassical solutions. The coherence properties of the outgoing scattered light are also analyzed, and it is shown that the corresponding correlation functions may provide detailed information about the internal dynamics of the system.
Geometrical Pumping with a Bose-Einstein Condensate.
Lu, H-I; Schemmer, M; Aycock, L M; Genkina, D; Sugawa, S; Spielman, I B
2016-05-20
We realized a quantum geometric "charge" pump for a Bose-Einstein condensate (BEC) in the lowest Bloch band of a novel bipartite magnetic lattice. Topological charge pumps in filled bands yield quantized pumping set by the global-topological-properties of the bands. In contrast, our geometric charge pump for a BEC occupying just a single crystal momentum state exhibits nonquantized charge pumping set by local-geometrical-properties of the band structure. Like topological charge pumps, for each pump cycle we observed an overall displacement (here, not quantized) and a temporal modulation of the atomic wave packet's position in each unit cell, i.e., the polarization.
Fidelity Decay in Trapped Bose-Einstein Condensates
Manfredi, G.; Hervieux, P.-A.
2008-02-08
The quantum coherence of a Bose-Einstein condensate is studied using the concept of quantum fidelity (Loschmidt echo). The condensate is confined in an elongated anharmonic trap and subjected to a small random potential such as that created by a laser speckle. Numerical experiments show that the quantum fidelity stays constant until a critical time, after which it drops abruptly over a single trap oscillation period. The critical time depends logarithmically on the number of condensed atoms and on the perturbation amplitude. This behavior may be observable by measuring the interference fringes of two condensates evolving in slightly different potentials.
Large atom number Bose-Einstein condensate machines
Streed, Erik W.; Chikkatur, Ananth P.; Gustavson, Todd L.; Boyd, Micah; Torii, Yoshio; Schneble, Dominik; Campbell, Gretchen K.; Pritchard, David E.; Ketterle, Wolfgang
2006-02-15
We describe experimental setups for producing large Bose-Einstein condensates of {sup 23}Na and {sup 87}Rb. In both, a high-flux thermal atomic beam is decelerated by a Zeeman slower and is then captured and cooled in a magneto-optical trap. The atoms are then transferred into a cloverleaf-style Ioffe-Pritchard magnetic trap and cooled to quantum degeneracy with radio-frequency-induced forced evaporation. Typical condensates contain 20x10{sup 6} atoms. We discuss the similarities and differences between the techniques used for producing large {sup 87}Rb and {sup 23}Na condensates in the context of nearly identical setups.
Large magnetic storage ring for Bose-Einstein condensates
Arnold, A. S.; Garvie, C. S.; Riis, E.
2006-04-15
Cold atomic clouds and Bose-Einstein condensates have been stored in a 10 cm diameter vertically oriented magnetic ring. An azimuthal magnetic field enables low-loss propagation of atomic clouds over a total distance of 2 m, with a heating rate of less than 50 nK/s. The vertical geometry was used to split an atomic cloud into two counter-rotating clouds which were recombined after one revolution. The system will be ideal for studying condensate collisions and ultimately Sagnac interferometry.
Rapidly rotating Bose-Einstein condensates in homogeneous traps
Correggi, M.; Rindler-Daller, T.; Yngvason, J.
2007-10-15
We extend the results of a previous paper on the Gross-Pitaevskii description of rotating Bose-Einstein condensates in two-dimensional traps to confining potentials of the form V(r)=r{sup s}, 2
Noise thermometry with two weakly coupled Bose-Einstein condensates.
Gati, Rudolf; Hemmerling, Börge; Fölling, Jonas; Albiez, Michael; Oberthaler, Markus K
2006-04-01
Here we report on the experimental investigation of thermally induced fluctuations of the relative phase between two Bose-Einstein condensates which are coupled via tunneling. The experimental control over the coupling strength and the temperature of the thermal background allows for the quantitative analysis of the phase fluctuations. Furthermore, we demonstrate the application of these measurements for thermometry in a regime where standard methods fail. With this we confirm that the heat capacity of an ideal Bose gas deviates from that of a classical gas as predicted by the third law of thermodynamics. PMID:16711972
Geometrical Pumping with a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Lu, H.-I.; Schemmer, M.; Aycock, L. M.; Genkina, D.; Sugawa, S.; Spielman, I. B.
2016-05-01
We realized a quantum geometric "charge" pump for a Bose-Einstein condensate (BEC) in the lowest Bloch band of a novel bipartite magnetic lattice. Topological charge pumps in filled bands yield quantized pumping set by the global—topological—properties of the bands. In contrast, our geometric charge pump for a BEC occupying just a single crystal momentum state exhibits nonquantized charge pumping set by local—geometrical—properties of the band structure. Like topological charge pumps, for each pump cycle we observed an overall displacement (here, not quantized) and a temporal modulation of the atomic wave packet's position in each unit cell, i.e., the polarization.
Collisional Dynamics of Half-Quantum Vortices in a Spinor Bose-Einstein Condensate.
Seo, Sang Won; Kwon, Woo Jin; Kang, Seji; Shin, Y
2016-05-01
We present an experimental study on the interaction and dynamics of half-quantum vortices (HQVs) in an antiferromagnetic spinor Bose-Einstein condensate. By exploiting the orbit motion of a vortex dipole in a trapped condensate, we perform a collision experiment of two HQV pairs, and observe that the scattering motions of the HQVs is consistent with the short-range vortex interaction that arises from nonsingular magnetized vortex cores. We also investigate the relaxation dynamics of turbulent condensates containing many HQVs, and demonstrate that spin wave excitations are generated by the collisional motions of the HQVs. The short-range vortex interaction and the HQV-magnon coupling represent two characteristics of the HQV dynamics in the spinor superfluid. PMID:27203331
Multiple dark-bright solitons in atomic Bose-Einstein condensates
Yan, D.; Kevrekidis, P. G.; Chang, J. J.; Hamner, C.; Engels, P.; Achilleos, V.; Frantzeskakis, D. J.; Carretero-Gonzalez, R.; Schmelcher, P.
2011-11-15
Motivated by recent experimental results, we present a systematic theoretical analysis of dark-bright-soliton interactions and multiple-dark-bright-soliton complexes in atomic two-component Bose-Einstein condensates. We study analytically the interactions between two dark-bright solitons in a homogeneous condensate and then extend our considerations to the presence of the trap. We illustrate the existence of robust stationary dark-bright-soliton ''molecules,'' composed of two or more solitons, which are formed due to the competition of the interaction forces between the dark- and bright-soliton components and the trap force. Our analysis is based on an effective equation of motion, derived for the distance between two dark-bright solitons. This equation provides equilibrium positions and characteristic oscillation frequencies of the solitons, which are found to be in good agreement with the eigenfrequencies of the anomalous modes of the system.
Collisional Dynamics of Half-Quantum Vortices in a Spinor Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Seo, Sang Won; Kwon, Woo Jin; Kang, Seji; Shin, Y.
2016-05-01
We present an experimental study on the interaction and dynamics of half-quantum vortices (HQVs) in an antiferromagnetic spinor Bose-Einstein condensate. By exploiting the orbit motion of a vortex dipole in a trapped condensate, we perform a collision experiment of two HQV pairs, and observe that the scattering motions of the HQVs is consistent with the short-range vortex interaction that arises from nonsingular magnetized vortex cores. We also investigate the relaxation dynamics of turbulent condensates containing many HQVs, and demonstrate that spin wave excitations are generated by the collisional motions of the HQVs. The short-range vortex interaction and the HQV-magnon coupling represent two characteristics of the HQV dynamics in the spinor superfluid.
Excitation spectra of a Bose-Einstein condensate with an angular spin-orbit coupling
NASA Astrophysics Data System (ADS)
Vasić, Ivana; Balaž, Antun
2016-09-01
A theoretical model of a Bose-Einstein condensate with angular spin-orbit coupling has recently been proposed and it has been established that a half-skyrmion represents the ground state in a certain regime of spin-orbit coupling and interaction. Here we investigate low-lying excitations of this phase by using the Bogoliubov method and numerical simulations of the time-dependent Gross-Pitaevskii equation. We find that a sudden shift of the trap bottom results in a complex two-dimensional motion of the system's center of mass that is markedly different from the response of a competing phase, and comprises two dominant frequencies. Moreover, the breathing mode frequency of the half-skyrmion is set by both the spin-orbit coupling and the interaction strength, while in the competing state it takes a universal value. Effects of interactions are especially pronounced at the transition between the two phases.
Phase-Imprinting of Bose-Einstein Condensates with Rydberg Impurities.
Mukherjee, Rick; Ates, Cenap; Li, Weibin; Wüster, Sebastian
2015-07-24
We show how the phase profile of Bose-Einstein condensates can be engineered through its interaction with localized Rydberg excitations. The interaction is made controllable and long range by off-resonantly coupling the condensate to another Rydberg state with laser light. Our technique allows the mapping of entanglement generated in systems of few strongly interacting Rydberg atoms onto much larger atom clouds in hybrid setups. As an example we discuss the creation of a spatial mesoscopic superposition state from a bright soliton. Additionally, the phase imprinted onto the condensate using the Rydberg excitations is a diagnostic tool for the latter. For example, a condensate time-of-flight image would permit reconstructing the pattern of an embedded Rydberg crystal.
Collisional Dynamics of Half-Quantum Vortices in a Spinor Bose-Einstein Condensate.
Seo, Sang Won; Kwon, Woo Jin; Kang, Seji; Shin, Y
2016-05-01
We present an experimental study on the interaction and dynamics of half-quantum vortices (HQVs) in an antiferromagnetic spinor Bose-Einstein condensate. By exploiting the orbit motion of a vortex dipole in a trapped condensate, we perform a collision experiment of two HQV pairs, and observe that the scattering motions of the HQVs is consistent with the short-range vortex interaction that arises from nonsingular magnetized vortex cores. We also investigate the relaxation dynamics of turbulent condensates containing many HQVs, and demonstrate that spin wave excitations are generated by the collisional motions of the HQVs. The short-range vortex interaction and the HQV-magnon coupling represent two characteristics of the HQV dynamics in the spinor superfluid.
Parametric amplification of matter waves in dipolar spinor Bose-Einstein condensates
Deuretzbacher, F.; Gebreyesus, G.; Santos, L.; Topic, O.; Scherer, M.; Luecke, B.; Ertmer, W.; Klempt, C.; Arlt, J.
2010-11-15
Spin-changing collisions may lead under proper conditions to the parametric amplification of matter waves in spinor Bose-Einstein condensates. Magnetic dipole-dipole interactions, although typically very weak in alkali-metal atoms, are shown to play a very relevant role in the amplification process. We show that these interactions may lead to a strong dependence of the amplification dynamics on the angle between the trap axis and the magnetic-field orientation. We analyze as well the important role played by magnetic-field gradients, which also modify strongly the amplification process. Magnetic-field gradients, hence, must be carefully controlled in future experiments, in order to observe clearly the effects of the dipolar interactions in the amplification dynamics.
Observation of Dipole-Induced Spin Texture in an Rb87 Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Eto, Yujiro; Saito, Hiroki; Hirano, Takuya
2014-05-01
We report the formation of spin texture resulting from the magnetic dipole-dipole interaction in a spin-2 Rb87 Bose-Einstein condensate. The spinor condensate is prepared in the transversely polarized spin state and the time evolution is observed under a magnetic field of 90 mG with a gradient of 3 mG /cm using Stern-Gerlach imaging. The experimental results are compared with numerical simulations of the Gross-Pitaevskii equation, which reveals that the observed spatial modulation of the longitudinal magnetization is due to the spin precession in an effective magnetic field produced by the dipole-dipole interaction. These results show that the dipole-dipole interaction has considerable effects even on spinor condensates of alkali metal atoms.
Lin, Yu-ju; Teper, Igor; Chin, Cheng; Vuletić, Vladan
2004-02-01
We investigate the stability of magnetically trapped atomic Bose-Einstein condensates and thermal clouds near the transition temperature at small distances 0.5 microm< or =d< or =10 microm from a microfabricated silicon chip. For a 2 microm thick copper film, the trap lifetime is limited by Johnson noise induced currents and falls below 1 s at a distance of 4 microm. A dielectric surface does not adversely affect the sample until the attractive Casimir-Polder potential significantly reduces the trap depth.
Bose-Einstein condensation on a manifold with non-negative Ricci curvature
Akant, Levent Ertuğrul, Emine Tapramaz, Ferzan Turgut, O. Teoman
2015-01-15
The Bose-Einstein condensation for an ideal Bose gas and for a dilute weakly interacting Bose gas in a manifold with non-negative Ricci curvature is investigated using the heat kernel and eigenvalue estimates of the Laplace operator. The main focus is on the nonrelativistic gas. However, special relativistic ideal gas is also discussed. The thermodynamic limit of the heat kernel and eigenvalue estimates is taken and the results are used to derive bounds for the depletion coefficient. In the case of a weakly interacting gas, Bogoliubov approximation is employed. The ground state is analyzed using heat kernel methods and finite size effects on the ground state energy are proposed. The justification of the c-number substitution on a manifold is given.
Entanglement generation between spinor Bose-Einstein condensates using Rydberg excitations
NASA Astrophysics Data System (ADS)
Idlas, Sandrine; Domenzain, Luis; Spreeuw, Robert; Byrnes, Tim
2016-02-01
We propose an experimental scheme of generating entangled states between two spinor Bose-Einstein condensates (BECs) using Rydberg excitations. Due to the strong interaction between Rydberg atoms, the Rydberg excitation creates an interaction between two closely located BECs. The method is suitable particularly for atom chip and permanent magnetic trap systems, which can create many BECs with an arbitrary two-dimensional geometry. We show two schemes of entangled state generation, based on stimulated Raman adiabatic passage (STIRAP) methods. The first method produces a symmetric state with total Sx spin zero between ground and excited states of the atoms using a single STIRAP pair, while the second produces a NOON state between hyperfine ground states using two STIRAP pairs. We show that despite the additional complexity of the BECs, it is possible to identify the initial and final adiabatic states exactly. We verify our theoretical predictions using numerical simulations on small boson number systems.
Modulational instability in binary spin-orbit-coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Bhat, Ishfaq Ahmad; Mithun, T.; Malomed, B. A.; Porsezian, K.
2015-12-01
We study modulation instability (MI) of flat states in two-component spin-orbit-coupled (SOC) Bose-Einstein condensates (BECs) in the framework of coupled Gross-Pitaevskii equations for two components of the pseudospinor wave function. The analysis is performed for equal densities of the components. Effects of the interaction parameters, Rabi coupling, and SOC on the MI are investigated. In particular, the results demonstrate that the SOC strongly alters the commonly known MI (immiscibility) condition, g122>g1g2 , for the binary superfluid with coefficients g1 ,2 and g12 of the intra- and interspecies repulsive interactions. In fact, the binary BEC is always subject to the MI under the action of the SOC, which implies that the ground state of the system is plausibly represented by a striped phase.
Bai, Xiao-Dong; Zhang, Mei; Xiong, Jun; Yang, Guo-Jian; Deng, Fu-Guo
2015-01-01
We investigate the formation of discrete breathers (DBs) and the dynamics of the mixture of two-species Bose-Einstein condensates (BECs) in open boundary optical lattices using the discrete nonlinear Schrödinger equations. The results show that the coupling of intra- and interspecies interaction can lead to the existence of pure single-species DBs and symbiotic DBs (i.e., two-species DBs). Furthermore, we find that there is a selective distillation phenomenon in the dynamics of the mixture of two-species BECs. One can selectively distil one species from the mixture of two-species BECs and can even control dominant species fraction by adjusting the intra- and interspecies interaction in optical lattices. Our selective distillation mechanism may find potential application in quantum information storage and quantum information processing based on multi-species atoms. PMID:26597592
Emergent patterns in a spin-orbit-coupled spin-2 Bose-Einstein condensate
Xu, Z. F.; Lue, R.; You, L.
2011-05-15
The ground-state phases of a spin-orbit (SO)-coupled atomic spin-2 Bose-Einstein condensate are studied. Interesting density patterns forme spontaneously are widespread due to the competition between SO coupling and spin-dependent interactions as in an SO-coupled spin-1 condensate. Unlike the case of spin-1 condensates, which are characterized by either a ferromagnetic or a polar phase in the absence of SO, spin-2 condensates can take a cyclic phase, where we find that the patterns formed due to SO are square or triangular in their spin-component densities for axial symmetric SO interaction. Both patterns are found to evolve continuously into striped forms with increased asymmetry of the SO coupling.
Tunable spin-orbit coupling and quantum phase transition in a trapped Bose-Einstein condensate.
Zhang, Yongping; Chen, Gang; Zhang, Chuanwei
2013-01-01
Spin-orbit coupling (SOC), the intrinsic interaction between a particle spin and its motion, is responsible for various important phenomena, ranging from atomic fine structure to topological condensed matter physics. The recent experimental breakthrough on the realization of SOC for ultra-cold atoms provides a completely new platform for exploring spin-orbit coupled superfluid physics. However, the SOC strength in the experiment is not tunable. In this report, we propose a scheme for tuning the SOC strength through a fast and coherent modulation of the laser intensities. We show that the many-body interaction between atoms, together with the tunable SOC, can drive a quantum phase transition (QPT) from spin-balanced to spin-polarized ground states in a harmonic trapped Bose-Einstein condensate (BEC), which resembles the long-sought Dicke QPT. We characterize the QPT using the periods of collective oscillations of the BEC, which show pronounced peaks and damping around the quantum critical point.
Quantum phases of Bose-Einstein condensates with synthetic spin-orbital-angular-momentum coupling
NASA Astrophysics Data System (ADS)
Qu, Chunlei; Sun, Kuei; Zhang, Chuanwei
2015-05-01
The experimental realization of emergent spin-orbit coupling through laser-induced Raman transitions in ultracold atoms paves the way for exploring novel superfluid physics and simulating exotic many-body phenomena. A recent proposal with the use of Laguerre-Gaussian lasers enables another fundamental type of coupling between spin and orbital angular momentum (SOAM) in ultracold atoms. We hereby study quantum phases of a realistic Bose-Einstein condensate (BEC) with this synthetic SOAM coupling in a disk-shaped geometry, respecting radial inhomogeneity of the Raman coupling. We find that the experimental system naturally resides in a strongly interacting regime in which the phase diagram significantly deviates from the single-particle picture. The interplay between SOAM coupling and interaction leads to rich structures in spin-resolved position and momentum distributions, including a stripe phase and various types of immiscible states. Our results would provide a guide for an experimental investigation of SOAM-coupled BECs.
Semi-classical dynamics of superradiant Rayleigh scattering in a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Müller, J. H.; Witthaut, D.; le Targat, R.; Arlt, J. J.; Polzik, E. S.; Hilliard, A. J.
2016-10-01
Due to its coherence properties and high optical depth, a Bose-Einstein condensate [BEC] provides an ideal setting to investigate collective atom-light interactions. Superradiant light scattering [SLS] in a BEC is a fascinating example of such an interaction. It is an analogous process to Dicke superradiance, in which an electronically inverted sample decays collectively, leading to the emission of one or more light pulses in a well-defined direction. Through time-resolved measurements of the superradiant light pulses emitted by an end-pumped BEC, we study the close connection of SLS with Dicke superradiance. A 1D model of the system yields good agreement with the experimental data and shows that the dynamics result from the structures that build up in the light and matter-wave fields along the BEC. This paves the way for exploiting the atom-photon correlations generated by the superradiance.
Observation of Bose-Einstein condensation in a strong synthetic magnetic field
NASA Astrophysics Data System (ADS)
Kennedy, Colin J.; Burton, William Cody; Chung, Woo Chang; Ketterle, Wolfgang
2015-10-01
Extensions of Berry’s phase and the quantum Hall effect have led to the discovery of new states of matter with topological properties. Traditionally, this has been achieved using magnetic fields or spin-orbit interactions, which couple only to charged particles. For neutral ultracold atoms, synthetic magnetic fields have been created that are strong enough to realize the Harper-Hofstadter model. We report the first observation of Bose-Einstein condensation in this system and study the Harper-Hofstadter Hamiltonian with one-half flux quantum per lattice unit cell. The diffraction pattern of the superfluid state directly shows the momentum distribution of the wavefunction, which is gauge-dependent. It reveals both the reduced symmetry of the vector potential and the twofold degeneracy of the ground state. We explore an adiabatic many-body state preparation protocol via the Mott insulating phase and observe the superfluid ground state in a three-dimensional lattice with strong interactions.
Mean-field predictions for a dipolar Bose-Einstein condensate with 164Dy
NASA Astrophysics Data System (ADS)
Zajec, Damir; Wunner, Günter
2015-11-01
Dipolar Bose-Einstein condensates are systems well suited for the investigation of effects caused by the nonlocal and anisotropic dipole-dipole interaction. In this paper we are interested in properties which are directly connected to the realization of a condensate with 164Dy , such as stability and phase diagrams. Additionally, we study the expansion of dipolar condensates and find signatures of the dipole-dipole interaction in terms of structured states and a deviation of the well-known inversion of the aspect ratio of the cloud during a time of flight. Our analysis is based on the extended Gross-Pitaevskii equation, which we solve numerically exactly on a grid by means of an imaginary- and real-time evolution.
Countersuperflow instability in miscible two-component Bose-Einstein condensates
Ishino, Shungo; Tsubota, Makoto; Takeuchi, Hiromitsu
2011-06-15
We study theoretically the instability of countersuperflow, i.e., two counterpropagating miscible superflows, in uniform two-component Bose-Einstein condensates. Countersuperflow instability causes mutual friction between the superfluids, causing a momentum exchange between the two condensates, when the relative velocity of the counterflow exceeds a critical value. The momentum exchange leads to nucleation of vortex rings from characteristic density patterns due to the nonlinear development of the instability. Expansion of the vortex rings drastically accelerates the momentum exchange, leading to a highly nonlinear regime caused by intervortex interaction and vortex reconnection between the rings. For a sufficiently large interaction between the two components, rapid expansion of the vortex rings causes isotropic turbulence and the global relative motion of the two condensates relaxes. The maximum vortex line density in the turbulence is proportional to the square of the relative velocity.
Spontaneously axisymmetry-breaking phase in a binary mixture of spinor Bose-Einstein condensates
Xu, Z. F.; Lue, R.; You, L.; Mei, J. W.
2010-11-15
We study the ground-state phases for a mixture of two atomic spin-1 Bose-Einstein condensates in the presence of a weak magnetic (B) field. The ground state is found to contain a broken-axisymmetry (BA) phase due to competitions among intraspecies and interspecies spin-exchange interactions and the linear Zeeman shifts. This is in contrast to the case of a single-species spin-1 condensate, where the axisymmetry breaking results from competitions among the linear and quadratic Zeeman shifts and the intraspecies ferromagnetic interaction. All other remaining ground-state phases for the mixture are found to preserve axisymmetry. We further elaborate on the ground-state phase diagram and calculate the Bogoliubov excitation spectra of the phases. For the BA phase, there exist three Goldstone modes that attempt to restore the broken U(1) and SO(2) symmetries.
Dynamics of vortex dipoles in anisotropic Bose-Einstein condensates
Goodman, Roy H.; Kevrekidis, P. G.; Carretero-González, R.
2015-04-14
We study the motion of a vortex dipole in a Bose-Einstein condensate confined to an anisotropic trap. We focus on a system of ODEs describing the vortices' motion, which is in turn a reduced model of the Gross-Pitaevskii equation describing the condensate's motion. Using a sequence of canonical changes of variables, we reduce the dimension and simplify the equations of motion. In this study, we uncover two interesting regimes. Near a family of periodic orbits known as guiding centers, we find that the dynamics is essentially that of a pendulum coupled to a linear oscillator, leading to stochastic reversals in the overall direction of rotation of the dipole. Near the separatrix orbit in the isotropic system, we find other families of periodic, quasi-periodic, and chaotic trajectories. In a neighborhood of the guiding center orbits, we derive an explicit iterated map that simplifies the problem further. Numerical calculations are used to illustrate the phenomena discovered through the analysis. Using the results from the reduced system, we are able to construct complex periodic orbits in the original, PDE, mean-field model for Bose-Einstein condensates, which corroborates the phenomenology observed in the reduced dynamical equations.
Dynamics of vortex dipoles in anisotropic Bose-Einstein condensates
Goodman, Roy H.; Kevrekidis, P. G.; Carretero-González, R.
2015-04-14
We study the motion of a vortex dipole in a Bose-Einstein condensate confined to an anisotropic trap. We focus on a system of ODEs describing the vortices' motion, which is in turn a reduced model of the Gross-Pitaevskii equation describing the condensate's motion. Using a sequence of canonical changes of variables, we reduce the dimension and simplify the equations of motion. In this study, we uncover two interesting regimes. Near a family of periodic orbits known as guiding centers, we find that the dynamics is essentially that of a pendulum coupled to a linear oscillator, leading to stochastic reversals inmore » the overall direction of rotation of the dipole. Near the separatrix orbit in the isotropic system, we find other families of periodic, quasi-periodic, and chaotic trajectories. In a neighborhood of the guiding center orbits, we derive an explicit iterated map that simplifies the problem further. Numerical calculations are used to illustrate the phenomena discovered through the analysis. Using the results from the reduced system, we are able to construct complex periodic orbits in the original, PDE, mean-field model for Bose-Einstein condensates, which corroborates the phenomenology observed in the reduced dynamical equations.« less
Skyrmions in a ferromagnetic Bose-Einstein condensate.
Al Khawaja, U; Stoof, H
2001-06-21
Multi-component Bose-Einstein condensates provide opportunities to explore experimentally the wealth of physics associated with the spin degrees of freedom. The ground-state properties and line-like vortex excitations of these quantum systems have been studied theoretically. In principle, nontrivial spin textures consisting of point-like topological excitations, or skyrmions, could exist in a multi-component Bose-Einstein condensate, owing to the superfluid nature of the gas. Although skyrmion excitations are already known in the context of nuclear physics and the quantum-Hall effect, creating these excitations in an atomic condensate would offer an opportunity to study their physical behaviour in much greater detail, while also enabling an ab initio comparison between theory and experiment. Here we investigate theoretically the stability of skyrmions in a fictitious spin-1/2 condensate of 87Rb atoms. We find that skyrmions can exist in such a gas only as a metastable state, but with a lifetime comparable to (or even longer than) the typical lifetime of the condensate itself.
Atom Interferometry on Sounding Rockets with Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Seidel, Stephan T.; Becker, Dennis; Lachmann, Maike D.; Herr, Waldemar; Rasel, Ernst M.; Quantus Collaboration
2016-05-01
One of the fundamental postulates of our description of nature is the universality of free fall, stating that the force exerted upon an object due to gravity is independent of its constitution. A precise test of this assumption is the comparison of the free fall of two ultra-cold clouds of different atomic species via atom interferometry. Since the sensitivity of the measurement is proportional to the square of the propagation time in the interferometer, it can be increased by performing the experiments in microgravity. In order to fully utilize the potential of the experiments the usage of a Bose-Einstein-Condensate as the initial state is necessary, because it is characterized by a small initial size and a low expansion velocity. As a step towards the transfer of such a system into space three sounding rocket missions with atom interferometers are currently being prepared. The launch of the first mission, aimed at the first demonstration of a Bose-Einstein-Condensate in space and an atom interferometer based on it is planned for 2016 from ESRANGE, Sweden. It will be followed by two more missions that extend the scientific goals to the creation of degenerate mixtures and dual-species atom interferometry. This research is funded by the German Space Agency DLR under Grant Number DLR 50 1131-37.
Interferometry with non-classical motional states of a Bose-Einstein condensate.
van Frank, S; Negretti, A; Berrada, T; Bücker, R; Montangero, S; Schaff, J-F; Schumm, T; Calarco, T; Schmiedmayer, J
2014-05-30
The Ramsey interferometer is a prime example of precise control at the quantum level. It is usually implemented using internal states of atoms, molecules or ions, for which powerful manipulation procedures are now available. Whether it is possible to control external degrees of freedom of more complex, interacting many-body systems at this level remained an open question. Here we demonstrate a two-pulse Ramsey-type interferometer for non-classical motional states of a Bose-Einstein condensate in an anharmonic trap. The control sequences used to manipulate the condensate wavefunction are obtained from optimal control theory and are directly optimized to maximize the interferometric contrast. They permit a fast manipulation of the atomic ensemble compared to the intrinsic decay processes and many-body dephasing effects. This allows us to reach an interferometric contrast of 92% in the experimental implementation.
Rapid rotation of a Bose-Einstein condensate in a harmonic plus quartic trap
Fetter, Alexander L.; Jackson, B.; Stringari, S.
2005-01-01
A two-dimensional rapidly rotating Bose-Einstein condensate in an anharmonic trap with quadratic and quartic radial confinement is studied analytically with the Thomas-Fermi approximation and numerically with the full time-independent Gross-Pitaevskii equation. The quartic trap potential allows the rotation speed {omega} to exceed the radial harmonic frequency {omega}{sub perpendicular}. In the regime {omega} > or approx. {omega}{sub perpendicular}, the condensate contains a dense vortex array (approximated as solid-body rotation for the analytical studies). At a critical angular velocity {omega}{sub h}, a central hole appears in the condensate. Numerical studies confirm the predicted value of {omega}{sub h}, even for interaction parameters that are not in the Thomas-Fermi limit. The behavior is also investigated at larger angular velocities, where the system is expected to undergo a transition to a giant vortex (with pure irrotational flow)
Fock-state dynamics in Raman photoassociation of Bose-Einstein condensates
Olsen, M.K.; Bradley, A.S.; Cavalcanti, S.B.
2004-09-01
By stochastic modeling of the process of Raman photoassociation of Bose-Einstein condensates, we show that, the farther the initial quantum state is from a coherent state, the farther the one-dimensional predictions are from those of the commonly used zero-dimensional approach. We compare the dynamics of condensates, initially in different quantum states, finding that, even when the quantum prediction for an initial coherent state is relatively close to the Gross-Pitaevskii prediction, an initial Fock state gives qualitatively different predictions. We also show that this difference is not present in a single-mode type of model, but that the quantum statistics assume a more important role as the dimensionality of the model is increased. This contrasting behavior in different dimensions, well known with critical phenomena in statistical mechanics, makes itself plainly visible here in a mesoscopic system and is a strong demonstration of the need to consider physically realistic models of interacting condensates.
Domain wall model in the galactic Bose-Einstein condensate halo
Souza, J.C.C. de; Pires, M.O.C. E-mail: marcelo.pires@ufabc.edu.br
2013-05-01
We assume that the galactic dark matter halo, considered composed of an axionlike particles Bose-Einstein condensate [1], can present topological defects, namely domain walls, arising as the dark soliton solution for the Gross-Pitaevskii equation in a self-graviting potential. We investigate the influence that such substructures would have in the gravitational interactions within a galaxy. We find that, for the simple domain wall model proposed, the effects are too small to be identified, either by means of a local measurement of the gradient of the gravitational field or by analysing galaxy rotation curves. In the first case, the gradient of the gravitational field in the vicinity of the domain wall would be 10{sup −31} (m/s{sup 2})/m. In the second case, the ratio of the tangential velocity correction of a star due to the presence of the domain wall to the velocity in the spherical symmetric case would be 10{sup −8}.
Quantum Enhancement of the Index of Refraction in a Bose-Einstein Condensate.
Bons, P C; de Haas, R; de Jong, D; Groot, A; van der Straten, P
2016-04-29
We study the index of refraction of an ultracold bosonic gas in the dilute regime. Using phase-contrast imaging with light detuned from resonance by several tens of linewidths, we image a single cloud of ultracold atoms for 100 consecutive shots, which enables the study of the scattering rate as a function of temperature and density using only a single cloud. We observe that the scattering rate is increased below the critical temperature for Bose-Einstein condensation by a factor of 3 compared to the single-atom scattering rate. We show that current atom-light interaction models to second order of the density show a similar increase, where the magnitude of the effect depends on the model that is used to calculate the pair-correlation function. This confirms that the effect of quantum statistics on the index of refraction is dominant in this regime. PMID:27176521
Functional Wigner representation of quantum dynamics of Bose-Einstein condensate
Opanchuk, B.; Drummond, P. D.
2013-04-15
We develop a method of simulating the full quantum field dynamics of multi-mode multi-component Bose-Einstein condensates in a trap. We use the truncated Wigner representation to obtain a probabilistic theory that can be sampled. This method produces c-number stochastic equations which may be solved using conventional stochastic methods. The technique is valid for large mode occupation numbers. We give a detailed derivation of methods of functional Wigner representation appropriate for quantum fields. Our approach describes spatial evolution of spinor components and properly accounts for nonlinear losses. Such techniques are applicable to calculating the leading quantum corrections, including effects such as quantum squeezing, entanglement, EPR correlations, and interactions with engineered nonlinear reservoirs. By using a consistent expansion in the inverse density, we are able to explain an inconsistency in the nonlinear loss equations found by earlier authors.
Classical dynamics of the optomechanical modes of a Bose-Einstein condensate in a ring cavity
Chen, W.; Goldbaum, D. S.; Bhattacharya, M.; Meystre, P.
2010-05-15
We consider a cavity optomechanical system consisting of a Bose-Einstein condensate (BEC) interacting with two counterpropagating traveling-wave modes in an optical ring cavity. In contrast to the more familiar case where the condensate is driven by the standing-wave field of a high-Q Fabry-Perot cavity we find that both symmetric and antisymmetric collective density side modes of the BEC are mechanically excited by the light field. In the semiclassical, mean-field limit where the light field and the zero-momentum mode of the condensate are treated classically the system is found to exhibit a rich multistable behavior, including the appearance of isolated branches of solutions (isolas). We also present examples of the dynamics of the system as input parameters such as the frequency of the driving lasers are varied.
Dark matter as a Bose-Einstein Condensate: the relativistic non-minimally coupled case
Bettoni, Dario; Colombo, Mattia; Liberati, Stefano E-mail: mattia.colombo@studenti.unitn.it
2014-02-01
Bose-Einstein Condensates have been recently proposed as dark matter candidates. In order to characterize the phenomenology associated to such models, we extend previous investigations by studying the general case of a relativistic BEC on a curved background including a non-minimal coupling to curvature. In particular, we discuss the possibility of a two phase cosmological evolution: a cold dark matter-like phase at the large scales/early times and a condensed phase inside dark matter halos. During the first phase dark matter is described by a minimally coupled weakly self-interacting scalar field, while in the second one dark matter condensates and, we shall argue, develops as a consequence the non-minimal coupling. Finally, we discuss how such non-minimal coupling could provide a new mechanism to address cold dark matter paradigm issues at galactic scales.
Confinement and precession of vortex pairs in coherently coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Tylutki, Marek; Pitaevskii, Lev P.; Recati, Alessio; Stringari, Sandro
2016-04-01
The dynamic behavior of vortex pairs in two-component coherently (Rabi) coupled Bose-Einstein condensates is investigated in the presence of harmonic trapping. We discuss the role of the surface tension associated with the domain wall connecting two vortices in condensates of atoms occupying different spin states and its effect on the precession of the vortex pair. The results, based on the numerical solution of the Gross-Pitaevskii equations, are compared with the predictions of an analytical macroscopic model and are discussed as a function of the size of the pair, the Rabi coupling, and the intercomponent interaction. We show that the increase of the Rabi coupling results in the disintegration of the domain wall into smaller pieces, connecting vortices of newly created vortex pairs. The resulting scenario is the analog of quark confinement and string breaking in quantum chromodynamics.
Multistability in an optomechanical system with a two-component Bose-Einstein condensate
Dong Ying; Ye Jinwu; Pu Han
2011-03-15
We investigate a system consisting of a two-component Bose-Einstein condensate interacting dispersively with a Fabry-Perot optical cavity where the two components of the condensate are resonantly coupled to each other by another classical field. The key feature of this system is that the atomic motional degrees of freedom and the internal pseudospin degrees of freedom are coupled to the cavity field simultaneously, hence an effective spin-orbital coupling within the condensate is induced by the cavity. The interplay among the atomic center-of-mass motion, the atomic collective spin, and the cavity field leads to a strong nonlinearity, resulting in multistable behavior in both matter wave and light wave at the few-photon level.
Vortices of a rotating two-component dipolar Bose-Einstein condensate in an optical lattice
NASA Astrophysics Data System (ADS)
Wang, Lin-Xue; Dong, Biao; Chen, Guang-Ping; Han, Wei; Zhang, Shou-Gang; Shi, Yu-Ren; Zhang, Xiao-Fei
2016-01-01
We consider a two-component Bose-Einstein condensate, which consists of both dipolar and scalar bosonic atoms, in a confinement that is composed of a harmonic oscillator and an underlying optical lattice set rotation. When the dipoles are polarized along the symmetry axis of the harmonic potential, the ground-state density distributions of such a system are investigated as a function of the relative strength between the dipolar and contact interactions, and of the rotation frequency. Our results show that the number of vortices and its related vortex structures of such a system depend strongly on such system parameters. The special two-component system considered here opens up alternate ways for exploring the rich physics of dipolar quantum gases.
Dual-species Bose-Einstein condensate of {sup 87}Rb and {sup 133}Cs
McCarron, D. J.; Cho, H. W.; Jenkin, D. L.; Koeppinger, M. P.; Cornish, S. L.
2011-07-15
We report the formation of a dual-species Bose-Einstein condensate of {sup 87}Rb and {sup 133}Cs in the same trapping potential. Our method exploits the efficient sympathetic cooling of {sup 133}Cs via elastic collisions with {sup 87}Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to 2x10{sup 4} atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the {sup 87}Rb during the cooling, we create single-species {sup 133}Cs condensates of up to 6x10{sup 4} atoms.
Visibility and stability of superstripes in a spin-orbit-coupled Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Martone, G. I.
2015-04-01
We consider a spin-1/2 Bose-Einstein condensate with equal Rashba and Dresselhaus spin-orbit coupling. After reviewing some relevant features of the quantum phases of the system, we present a short study on how their properties are changed by the presence of non-zero magnetic detunings and spin-asymmetric interactions. At small values of the Raman coupling and of the magnetic field the so-called stripe phase occurs, which displays both superfluidity and periodic density modulations, in analogy with supersolids. We finally review a recent proposal (Phys. Rev. A 90, 041604) to improve the visibility of the fringes, based on the space separation of the two spin components into a 2D bi-layer configuration and on the application of a π/2 Bragg pulse, and we show that this new configuration also yields a sizable increase of the stability of the stripe phase against magnetic fluctuations.
Mean-field dynamics of spin-orbit coupled Bose-Einstein condensates.
Zhang, Yongping; Mao, Li; Zhang, Chuanwei
2012-01-20
Spin-orbit coupling (SOC), the interaction between the spin and momentum of a quantum particle, is crucial for many important condensed matter phenomena. The recent experimental realization of SOC in neutral bosonic cold atoms provides a new and ideal platform for investigating spin-orbit coupled quantum many-body physics. In this Letter, we derive a generic Gross-Pitaevskii equation as the starting point for the study of many-body dynamics in spin-orbit coupled Bose-Einstein condensates. We show that different laser setups for realizing the same SOC may lead to different mean-field dynamics. Various ground state phases (stripe, phase separation, etc.) of the condensate are found in different parameter regions. A new oscillation period induced by the SOC, similar to the Zitterbewegung oscillation, is found in the center-of-mass motion of the condensate.
Spin-orbit angular momentum coupling in a spin-1 Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Chen, Li; Pu, Han; Zhang, Yunbo
2016-01-01
We propose a simple model with spin and orbit angular momentum coupling in a spin-1 Bose-Einstein condensate, where three internal atomic states are Raman coupled by a pair of copropagating Laguerre-Gaussian beams. The resulting Raman transition imposes a transfer of orbital angular momentum between photons and the condensate in a spin-dependent way. Focusing on a regime where the single-particle ground state is nearly threefold degenerate, we show that the weak interatomic interaction in the condensate produces a rich phase diagram, and that a many-body Rabi oscillation between two quantum phases can be induced by a sudden quench of the quadratic Zeeman shift. We carried out our calculations using both a variational method and a full numerical method, and found excellent agreement.
Dicke-type phase transition in a spin-orbit-coupled Bose-Einstein condensate.
Hamner, Chris; Qu, Chunlei; Zhang, Yongping; Chang, JiaJia; Gong, Ming; Zhang, Chuanwei; Engels, Peter
2014-06-04
Spin-orbit-coupled Bose-Einstein condensates (BECs) provide a powerful tool to investigate interesting gauge field-related phenomena. Here we study the ground state properties of such a system and show that it can be mapped to the well-known Dicke model in quantum optics, which describes the interactions between an ensemble of atoms and an optical field. A central prediction of the Dicke model is a quantum phase transition between a superradiant phase and a normal phase. We detect this transition in a spin-orbit-coupled BEC by measuring various physical quantities across the phase transition. These quantities include the spin polarization, the relative occupation of the nearly degenerate single-particle states, the quantity analogous to the photon field occupation and the period of a collective oscillation (quadrupole mode). The applicability of the Dicke model to spin-orbit-coupled BECs may lead to interesting applications in quantum optics and quantum information science.
Vector solitons in a spin-orbit-coupled spin-2 Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Gautam, Sandeep; Adhikari, S. K.
2015-06-01
Five-component minimum-energy bound states and mobile vector solitons of a spin-orbit-coupled quasi-one-dimensional hyperfine-spin-2 Bose-Einstein condensate are studied using the numerical solution and variational approximation of a mean-field model. Two distinct types of solutions with single-peak and multipeak density distribution of the components are identified in different domains of interaction parameters. From an analysis of Galilean invariance and time-reversal symmetry of the Hamiltonian, we establish that vector solitons with multipeak density distribution preserve time-reversal symmetry, but they cannot propagate while maintaining the shape of individual components. However, those with single-peak density distribution violate time-reversal symmetry of the Hamiltonian, but they can propagate with a constant velocity and maintain the shape of individual components.
Vortices in a rotating Bose-Einstein condensate under extreme elongation
Sanchez-Lotero, P.; Palacios, J.J.
2005-10-15
We investigate a nonaxisymmetric rotating Bose-Einstein condensate (BEC) in the limit of rotation frequency for which the BEC transforms into a quasi-one-dimensional system. We compute the vortex lattice wave function by minimizing the Gross-Pitaevskii energy functional in the lowest Landau level approximation for different confinement potentials. The condensate typically presents a changing number of vortex rows as a function of the interaction strength or rotation-confinement ratio. More specifically, the vortex lattices can be classified into two classes according to their symmetry with respect to the longitudinal axis. These two classes correspond to different local minima of the energy functional and evolve independently as a function of the various parameters.
Dark soliton beats in the time-varying background of Bose-Einstein condensates
Wu Lei; Li Lu; Zhang Jiefang
2009-07-15
We investigate the dynamics of dark solitons in one-dimensional Bose-Einstein condensates. In the large particle limit, by introducing the lens-type transformation, we find that the macroscopic wave function evolves self-similarly when its initial profile strays from that of the equilibrium state, which provides a time-varying background for the propagation of dark solitons. The interaction of dark solitons with this kind of background is studied both analytically and numerically. We find that the center-of-mass motion of the dark soliton is deeply affected by the time-varying background, and the beating phenomena of dark soliton emerge when the intrinsic frequency of the dark soliton approaches that of the background. Lastly, we investigate the propagation of dark solitons in the freely expanding background.
Collisions of Solitons and Vortex Rings in Cylindrical Bose-Einstein Condensates
Komineas, Stavros; Brand, Joachim
2005-09-09
Interactions of solitary waves in a cylindrically confined Bose-Einstein condensate are investigated by simulating their head-on collisions. Slow vortex rings and fast solitons are found to collide elastically contrary to the situation in the three-dimensional homogeneous Bose gas. Strongly inelastic collisions are absent for low density condensates but occur at higher densities for intermediate velocities. The scattering behavior is rationalized by use of dispersion diagrams. During inelastic collisions, spherical shell-like structures of low density are formed and they eventually decay into depletion droplets with solitary-wave features. The relation to similar shells observed in a recent experiment by Ginsberg et al. [Phys. Rev. Lett. 94, 040403 (2005)] is discussed.
Scalable Bose-Einstein-condensate Sagnac interferometer in a linear trap
Burke, J. H. T.; Sackett, C. A.
2009-12-15
We demonstrate a two-dimensional atom interferometer in a harmonic magnetic waveguide using a Bose-Einstein condensate. Such an interferometer could measure rotation using the Sagnac effect. Compared to free space interferometers, larger interactions times and enclosed areas can in principle be achieved, since the atoms are not in free fall. In this implementation, we induce the atoms to oscillate along one direction by displacing the trap center. We then split and recombine the atoms along an orthogonal direction using an off-resonant optical standing wave. We enclose a maximum effective area of 0.1 mm{sup 2} limited by fluctuations in the initial velocity and by the coherence time of the interferometer. We argue that this arrangement is scalable to enclose larger areas by increasing the coherence time and then making repeated loops.
Quantum Enhancement of the Index of Refraction in a Bose-Einstein Condensate.
Bons, P C; de Haas, R; de Jong, D; Groot, A; van der Straten, P
2016-04-29
We study the index of refraction of an ultracold bosonic gas in the dilute regime. Using phase-contrast imaging with light detuned from resonance by several tens of linewidths, we image a single cloud of ultracold atoms for 100 consecutive shots, which enables the study of the scattering rate as a function of temperature and density using only a single cloud. We observe that the scattering rate is increased below the critical temperature for Bose-Einstein condensation by a factor of 3 compared to the single-atom scattering rate. We show that current atom-light interaction models to second order of the density show a similar increase, where the magnitude of the effect depends on the model that is used to calculate the pair-correlation function. This confirms that the effect of quantum statistics on the index of refraction is dominant in this regime.
Bose-Einstein quantum phase transition in an optical lattice model
Aizenman, Michael; Lieb, Elliott H.; Seiringer, Robert; Solovej, Jan Philip; Yngvason, Jakob
2004-08-01
Bose-Einstein condensation (BEC) in cold gases can be turned on and off by an external potential, such as that presented by an optical lattice. We present a model of this phenomenon which we are able to analyze rigorously. The system is a hard core lattice gas at half of the maximum density and the optical lattice is modeled by a periodic potential of strength {lambda}. For small {lambda} and temperature, BEC is proved to occur, while at large {lambda} or temperature there is no BEC. At large {lambda} the low-temperature states are in a Mott insulator phase with a characteristic gap that is absent in the BEC phase. The interparticle interaction is essential for this transition, which occurs even in the ground state. Surprisingly, the condensation is always into the p=0 mode in this model, although the density itself has the periodicity of the imposed potential.
Theory of single-shot phase contrast imaging in spinor Bose-Einstein condensates.
Ilo-Okeke, Ebubechukwu O; Byrnes, Tim
2014-06-13
We introduce a theoretical framework for single-shot phase contrast imaging (PCI) measurements of spinor Bose-Einstein condensates (BECs). Our model allows for the simple calculation of the quantum backaction resulting from the measurement, and the amount of information that is read out. We find that there is an optimum time Gτ ∼ 1/N for the light-matter interaction (G is the ac Stark shift frequency, N is the number of particles in the BEC), where the maximum amount of information can be read out from the BEC. A universal information-disturbance tradeoff law ε(F)ε(G) ∝ 1/N(2) is found where ε(F) is the amount of backaction and ε(G) is the estimation error. The PCI measurement can also be found to be a direct probe of the quantum fluctuations of the BEC, via the noise of the PCI signal.
Vortex structures of rotating spin-orbit-coupled Bose-Einstein condensates
Zhou Xiangfa; Zhou Jing; Wu Congjun
2011-12-15
We consider the quasi-two-dimensional two-component Bose-Einstein condensates with Rashba spin-orbit (SO) coupling in a rotating trap. The rotation angular velocity couples to the mechanical angular momentum, which contains a noncanonical part arising from SO coupling. The effects of an external Zeeman term favoring spin polarization along the radial direction is also considered, which has the same form as the noncanonical part of the mechanical angular momentum. The rotating condensate exhibits a variety of rich structures by varying the strengths of the trapping potential and interaction. With a strong trapping potential, the condensate exhibits a half-quantum vortex-lattice configuration. Such a configuration is driven to the normal one by introducing the external radial Zeeman field. In the case of a weak trap potential, the condensate exhibits a multidomain pattern of plane-wave states under the external radial Zeeman field.
Impurities as a quantum thermometer for a Bose-Einstein condensate
Sabín, Carlos; White, Angela; Hackermuller, Lucia; Fuentes, Ivette
2014-01-01
We introduce a primary thermometer which measures the temperature of a Bose-Einstein Condensate in the sub-nK regime. We show, using quantum Fisher information, that the precision of our technique improves the state-of-the-art in thermometry in the sub-nK regime. The temperature of the condensate is mapped onto the quantum phase of an atomic dot that interacts with the system for short times. We show that the highest precision is achieved when the phase is dynamical rather than geometric and when it is detected through Ramsey interferometry. Standard techniques to determine the temperature of a condensate involve an indirect estimation through mean particle velocities made after releasing the condensate. In contrast to these destructive measurements, our method involves a negligible disturbance of the system. PMID:25241663
Kottke, M.; Schulte, T.; Hellweg, D.; Drenkelforth, S.; Ertmer, W.; Arlt, J. J.; Cacciapuoti, L.
2005-11-15
We measure the frequency of the low m=0 quadrupolar excitation mode of weakly interacting Bose-Einstein condensates in the transition region from the three-dimensional (3D) to the 1D mean-field regime. Various effects shifting the frequency of the mode are discussed. In particular we take the dynamic coupling of the condensate with the thermal component at finite temperature into account using a time-dependent Hartree-Fock-Bogoliubov treatment developed by Giorgini [Phys. Rev. A, 61, 063615 (2000)]. We show that the frequency rises in the transition from 3D to 1D, in good agreement with the theoretical prediction of Menotti and Stringari [Phys. Rev. A 66, 043610 (2002)].
Matter-wave interference versus spontaneous pattern formation in spinor Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Witkowski, Marcin; Gartman, Rafał; Nagórny, Bartłomiej; Piotrowski, Marcin; Płodzień, Marcin; Sacha, Krzysztof; Szczepkowski, Jacek; Zachorowski, Jerzy; Zawada, Michał; Gawlik, Wojciech
2013-08-01
We describe effects of matter-wave interference of spinor states in the 87Rb Bose-Einstein condensate. The components of the F=2 manifold are populated by forced Majorana transitions and then fall freely due to gravity in an applied magnetic field. Weak inhomogeneities of the magnetic field, present in the experiment, impose relative velocities onto different mF components, which show up as interference patterns upon measurement of atomic density distributions with a Stern-Gerlach imaging method. We show that interference effects may appear in experiments even if gradients of the magnetic field components are eliminated but higher-order inhomogeneity is present and the duration of the interaction is long enough. In particular, we show that the resulting matter-wave interference patterns can mimic spontaneous pattern formation in the quantum gas.
Dynamic effects of a Feshbach resonance on Bragg scattering from a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Sahlberg, Catarina E.; Ballagh, R. J.; Gardiner, C. W.
2013-04-01
We present a theoretical model for Bragg scattering from a Bose-Einstein condensate (BEC) in the vicinity of a magnetic Feshbach resonance, using a two-c-field formalism, one c field for the atom and the other for a molecule formed of two atoms. We use this model to numerically simulate an experiment [Papp , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.101.135301 101, 135301 (2008)] investigating the effects of strong interactions on the Bragg spectrum from a 85Rb BEC. Results from these simulations and from our previous calculations using an atom-molecule Bogoliubov approach are in very good quantitative agreement with the experimental results, confirming the importance of the resonance bound state in the dynamics of the condensate for fast experiments like Bragg scattering.
Interferometry with non-classical motional states of a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
van Frank, S.; Negretti, A.; Berrada, T.; Bücker, R.; Montangero, S.; Schaff, J.-F.; Schumm, T.; Calarco, T.; Schmiedmayer, J.
2014-05-01
The Ramsey interferometer is a prime example of precise control at the quantum level. It is usually implemented using internal states of atoms, molecules or ions, for which powerful manipulation procedures are now available. Whether it is possible to control external degrees of freedom of more complex, interacting many-body systems at this level remained an open question. Here we demonstrate a two-pulse Ramsey-type interferometer for non-classical motional states of a Bose-Einstein condensate in an anharmonic trap. The control sequences used to manipulate the condensate wavefunction are obtained from optimal control theory and are directly optimized to maximize the interferometric contrast. They permit a fast manipulation of the atomic ensemble compared to the intrinsic decay processes and many-body dephasing effects. This allows us to reach an interferometric contrast of 92% in the experimental implementation.
Watching a Bose-Einstein condensate crystallize
Wilson, Mark
2010-07-15
In 1954 Robert Dicke predicted a remarkable phenomenon. Imagine a dense cloud of two-level atoms in an excited state that can radiatively decay. Because each atom typically decays independently of its neighbors, the cloud is a collection of incoherent emitters. But, he argued, if the atoms interact coherently, through the same optical field into which they emit their photons, they would spontaneously and collectively radiate coherent and highly polarized light--an effect Dicke named superradiance.
Bloch oscillations and mean-field effects of Bose-Einstein condensates in 1D optical lattices.
Morsch, O; Müller, J H; Cristiani, M; Ciampini, D; Arimondo, E
2001-10-01
We have loaded Bose-Einstein condensates into one-dimensional, off-resonant optical lattices and accelerated them by chirping the frequency difference between the two lattice beams. For small values of the lattice well depth, Bloch oscillations were observed. Reducing the potential depth further, Landau-Zener tunneling out of the lowest lattice band, leading to a breakdown of the oscillations, was also studied and used as a probe for the effective potential resulting from mean-field interactions as predicted by Choi and Niu [Phys. Rev. Lett. 82, 2022 (1999)]. The effective potential was measured for various condensate densities and trap geometries, yielding good qualitative agreement with theoretical calculations.
Huang, C. C.; Liu, C. H.; Wu, W. C.
2010-04-15
The behaviors of a rapidly rotating Bose-Einstein condensate under extreme elongation in a two-dimensional anisotropic harmonic plus quartic trap are investigated. Due to the quartic trap, the system remains stable at high rotating velocity, {Omega}{>=}{omega}{sub perpendicular} ({omega}{sub perpendicular} is the radial harmonic trap frequency), and vortex lattices form even in the absence of the repulsive s-wave interaction (g). When g is present, the interplay between g and the quartic trap potential can lead to rich vortex lattice transition states as a function of {Omega}, to which vortex lattices vanish eventually at some higher {Omega}.
Dynamical quantum phase transition of a two-component Bose-Einstein condensate in an optical lattice
Collin, Anssi; Martikainen, Jani-Petri; Larson, Jonas
2010-01-15
We study the dynamics of a two-component Bose-Einstein condensate where the two components are coupled via an optical lattice. In particular, we focus on the dynamics as one drives the system through a critical point of a first-order phase transition characterized by a jump in the internal populations. Solving the time-dependent Gross-Pitaevskii equation, we analyze the breakdown of adiabaticity, impact of nonlinear atom-atom scattering, and role of a harmonic trapping potential. Our findings demonstrate that the phase transition is resilient to both contact interaction between atoms and external trapping confinement.
Near-resonant spatial images of confined Bose-Einstein condensates in a 4-Dee magnetic bottle
NASA Astrophysics Data System (ADS)
Vestergaard Hau, Lene; Busch, B. D.; Liu, Chien; Dutton, Zachary; Burns, Michael M.; Golovchenko, J. A.
1998-07-01
We present quantitative measurements of the spatial density profile of Bose-Einstein condensates of sodium atoms confined in a 4-Dee magnetic bottle. The condensates are imaged in transmission with near-resonant laser light. We demonstrate that the Thomas-Fermi surface of a condensate can be determined to better than 1%. More generally, we obtain excellent agreement with mean-field theory. We conclude that precision measurements of atomic scattering lengths and interactions between phase-separated cold atoms in a harmonic trap can be performed with high precision using this method.
On the Josephson effect in a Bose-Einstein condensate subject to a density-dependent gauge potential
NASA Astrophysics Data System (ADS)
Edmonds, M. J.; Valiente, M.; Öhberg, P.
2013-07-01
We investigate the coherent dynamics of a Bose-Einstein condensate in a double well, subject to a density-dependent gauge potential. Further, we derive the nonlinear Josephson equations that allow us to understand the many-body system in terms of a classical Hamiltonian that describes the motion of a nonrigid pendulum with an initial angular offset. Finally we analyse the phase-space trajectories of the system, and describe how the self-trapping is affected by the presence of an interacting gauge potential.
Vortex formation by merging multiple trapped Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Weiler, Chad; Neely, Tyler; Scherer, David; Anderson, Brian
2007-06-01
We have experimentally studied the merging of three trapped Bose-Einstein condensates. We find that, depending on the rate of merging, the final single BEC may contain a single vortex core (for slow merging rates), or multiple cores (for fast merging rates). Similarly, a triple-well trap may initiate the formation of three isolated BECs, but if the barriers between the wells are weak enough, the condensates merge together during their growth; this process can also lead to the formation of vortices in the final BEC. We interpret both scenarios in terms of interference between the initial uncorrelated condensates with indeterminate relative phases. We will discuss the results and interpretation of this experiment (D.R. Scherer, C.N. Weiler, T.W. Neely, B.P. Anderson, cond-mat/0610187, to be published in Phys. Rev. Lett.).
Vortex signatures in annular Bose-Einstein condensates
Cozzini, M.; Stringari, S.; Jackson, B.
2006-01-15
We consider a Bose-Einstein condensate confined in a 'Mexican hat' or sombrero potential, with a quartic minus quadratic radial dependence. We find conditions under which the ground state is annular in shape, with a hole in the center of the condensate. Rotation leads to the appearance of stable multiply quantized vortices, giving rise to a superfluid flow around the ring. The collective modes of the system are explored both numerically and analytically using the Gross-Pitaevskii and hydrodynamic equations. Potential experimental schemes to detect vorticity are proposed and evaluated, which include measuring the splitting of collective-mode frequencies, observing expansion following release from the trap, and probing the momentum distribution of the condensate.
Thermalization of gluons with Bose-Einstein condensation.
Xu, Zhe; Zhou, Kai; Zhuang, Pengfei; Greiner, Carsten
2015-05-01
We study the thermalization of gluons far from thermal equilibrium in relativistic kinetic theory. The initial distribution of gluons is assumed to resemble that in the early stage of ultrarelativistic heavy ion collisions. Only elastic scatterings in static, nonexpanding gluonic matter are considered. At first we show that the occurrence of condensation in the limit of vanishing particle mass requires a general constraint for the scattering matrix element. Then the thermalization of gluons with Bose-Einstein condensation is demonstrated in a transport calculation. We see a continuously increasing overpopulation of low energy gluons, followed by a decrease to the equilibrium distribution, when the condensation occurs. The times of the completion of the gluon condensation and of the entropy production are calculated. These times scale inversely with the energy density.
Spatial structure of a collisionally inhomogeneous Bose-Einstein condensate
Li, Fei; Zhang, Dongxia; Rong, Shiguang; Xu, Ying
2013-11-15
The spatial structure of a collisionally inhomogeneous Bose-Einstein condensate (BEC) in an optical lattice is studied. A spatially dependent current with an explicit analytic expression is found in the case with a spatially dependent BEC phase. The oscillating amplitude of the current can be adjusted by a Feshbach resonance, and the intensity of the current depends heavily on the initial and boundary conditions. Increasing the oscillating amplitude of the current can force the system to pass from a single-periodic spatial structure into a very complex state. But in the case with a constant phase, the spatially dependent current disappears and the Melnikov chaotic criterion is obtained via a perturbative analysis in the presence of a weak optical lattice potential. Numerical simulations show that a strong optical lattice potential can lead BEC atoms to a state with a chaotic spatial distribution via a quasiperiodic route.
Neural networks using two-component Bose-Einstein condensates
Byrnes, Tim; Koyama, Shinsuke; Yan, Kai; Yamamoto, Yoshihisa
2013-01-01
The authors previously considered a method of solving optimization problems by using a system of interconnected network of two component Bose-Einstein condensates (Byrnes, Yan, Yamamoto New J. Phys. 13, 113025 (2011)). The use of bosonic particles gives a reduced time proportional to the number of bosons N for solving Ising model Hamiltonians by taking advantage of enhanced bosonic cooling rates. Here we consider the same system in terms of neural networks. We find that up to the accelerated cooling of the bosons the previously proposed system is equivalent to a stochastic continuous Hopfield network. This makes it clear that the BEC network is a physical realization of a simulated annealing algorithm, with an additional speedup due to bosonic enhancement. We discuss the BEC network in terms of neural network tasks such as learning and pattern recognition and find that the latter process may be accelerated by a factor of N. PMID:23989391
Internal Josephson oscillations for distinct momenta Bose-Einstein condensates
Lim, Lih-King; Troppenz, T.; Morais Smith, C.
2011-11-15
The internal Josephson oscillations between an atomic Bose-Einstein condensate (BEC) and a molecular one are studied for atoms in a square optical lattice subjected to a staggered gauge field. The system is described by a Bose-Hubbard model with complex and anisotropic hopping parameters that are different for each species, i.e., atoms and molecules. When the flux per plaquette for each species is small, the system oscillates between two conventional zero-momentum condensates. However, there is a regime of parameters in which Josephson oscillations between a vortex-carrying atomic condensate (finite momentum BEC) and a conventional zero-momentum molecular condensate may be realized. The experimental observation of the oscillations between these qualitatively distinct BEC's is possible with state-of-the-art Ramsey interference techniques.
Nonlinear waves in coherently coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Congy, T.; Kamchatnov, A. M.; Pavloff, N.
2016-04-01
We consider a quasi-one-dimensional two-component Bose-Einstein condensate subject to a coherent coupling between its components, such as realized in spin-orbit coupled condensates. We study how nonlinearity modifies the dynamics of the elementary excitations. The spectrum has two branches, which are affected in different ways. The upper branch experiences a modulational instability, which is stabilized by a long-wave-short-wave resonance with the lower branch. The lower branch is stable. In the limit of weak nonlinearity and small dispersion it is described by a Korteweg-de Vries equation or by the Gardner equation, depending on the value of the parameters of the system.
Formation of molecules in an expanding Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Yurovsky, Vladimir; Ben-Reuven, Abraham
2004-05-01
A mean field theory [1] is extended to an inhomogeneous case of expanding hybrid atom-molecule Bose-Einstein condensates. This theory is applied to the recent MPI experiments [2] on ^87Rb demonstrating the formation of ultracold molecules due to Feshbach resonance. The subsequent dissociation of the molecules is treated using a non-mean-field parametric approximation [3]. The latter method is also used in determining optimal conditions for the formation of molecular BEC. [1] V. A. Yurovsky, A. Ben-Reuven, P. S. Julienne and C. J. Williams, Phys. Rev. A 60, R765 (1999); Phys. Rev. A 62, 043605 (2000). [2] S. Dürr, T. Volz, A. Marte, and G. Rempe, Phys. Rev. Lett. 92, 020406 (2004). [3] V. A. Yurovsky and A. Ben-Reuven, Phys. Rev. A 67, 043611 (2003).
STIRAP schemes for atomic Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Thomasen, Andreas M. D.; Byrnes, Tim
2016-09-01
In coherent control of Bose-Einstein condensates (BEC) the major limitation to successful high fidelity transfer using optical Raman transitions is spontaneous emission of radiation and the decoherence that this causes. We present a scheme based on stimulated Raman adiabatic passage (STIRAP) designed specifically for Rubidium 87. STIRAP is a method of population transfer that relies on the adiabatic theorem of quantum mechanics. Instead of transferring population between Hamiltonian ground states, one adiabatically evolves the ground states into some desired superposition. We show that one may thereby implement arbitrary rotations of spinor BECs with extremely high fidelities. Our simulations show that given a BEC with N = 104 atoms, we may do an arbitrary unitary rotation with an infidelity of about 10-7 that takes approximately 100 ns.
Bose-Einstein Condensates with Large Number of Vortices
Ho, Tin-Lun
2001-08-06
We show that as the number of vortices in a three dimensional Bose-Einstein condensate increases, the system reaches a ''quantum Hall'' regime where the density profile is a Gaussian in the xy plane and an inverted parabolic profile along z . The angular momentum of the system increases as the vortex lattice shrinks. However, Coriolis force prevents the unit cell of the vortex lattice from shrinking beyond a minimum size. Although the recent MIT experiment is not exactly in the quantum Hall regime, it is close enough for the present results to be used as a guide. The quantum Hall regime can be easily reached by moderate changes of the current experimental parameters.
Kinetic approach to a relativistic Bose-Einstein condensate.
Meistrenko, Alex; van Hees, Hendrik; Zhou, Kai; Greiner, Carsten
2016-03-01
We apply a Boltzmann approach to the kinetic regime of a relativistic Bose-Einstein condensate of scalar bosons by decomposing the one-particle distribution function in a condensate part and a nonzero momentum part of excited modes, leading to a coupled set of evolution equations which are then solved efficiently with an adaptive higher order Runge-Kutta scheme. We compare our results to the partonic cascade Monte Carlo simulation BAMPS for a critical but far from equilibrium case of massless bosons. Motivated by the color glass condensate initial conditions in QCD with a strongly overpopulated initial glasma state, we also discuss the time evolution starting from an overpopulated initial distribution function of massive scalar bosons. In this system a self-similar evolution of the particle cascade with a nonrelativistic turbulent scaling in the infrared sector is observed as well as a relativistic exponent for the direct energy cascade, confirming a weak wave turbulence in the ultraviolet region.
Bell correlations in a Bose-Einstein condensate.
Schmied, Roman; Bancal, Jean-Daniel; Allard, Baptiste; Fadel, Matteo; Scarani, Valerio; Treutlein, Philipp; Sangouard, Nicolas
2016-04-22
Characterizing many-body systems through the quantum correlations between their constituent particles is a major goal of quantum physics. Although entanglement is routinely observed in many systems, we report here the detection of stronger correlations--Bell correlations--between the spins of about 480 atoms in a Bose-Einstein condensate. We derive a Bell correlation witness from a many-particle Bell inequality involving only one- and two-body correlation functions. Our measurement on a spin-squeezed state exceeds the threshold for Bell correlations by 3.8 standard deviations. Our work shows that the strongest possible nonclassical correlations are experimentally accessible in many-body systems and that they can be revealed by collective measurements.
Mode locking of a driven Bose-Einstein condensate
Nicolin, Alexandru I.; Jensen, Mogens H.; Carretero-Gonzalez, R.
2007-03-15
We consider the dynamics of a driven Bose-Einstein condensate with positive scattering length. Employing an accustomed variational treatment we show that when the scattering length is time modulated as a(1+{epsilon} sin[{omega}(t)t]), where {omega}(t) increases linearly in time, i.e., {omega}(t)={gamma}t, the response frequency of the condensate locks to the eigenfrequency for small values of {epsilon} and {gamma}. A simple analytical model is presented which explains this phenomenon by mapping it to an auto-resonance, i.e., close to resonance the reduced equations describing the collective behavior of the condensate are equivalent to those of a virtual particle trapped in a finite-depth energy minimum of an effective potential.
Matter-wave recombiners for trapped Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Berrada, T.; van Frank, S.; Bücker, R.; Schumm, T.; Schaff, J.-F.; Schmiedmayer, J.; Julía-Díaz, B.; Polls, A.
2016-06-01
Interferometry with trapped atomic Bose-Einstein condensates (BECs) requires the development of techniques to recombine the two paths of the interferometer and map the accumulated phase difference to a measurable atom number difference. We have implemented and compared two recombining procedures in a double-well-based BEC interferometer. The first procedure utilizes the bosonic Josephson effect and controlled tunneling of atoms through the potential barrier, similar to laser light in an optical fiber coupler. The second one relies on the interference of the reflected and transmitted parts of the BEC wave function when impinging on the potential barrier, analogous to light impinging on a half-silvered mirror. Both schemes were implemented successfully, yielding an interferometric contrast of ˜20 % and 42% respectively. Building efficient matter-wave recombiners represents an important step towards the coherent manipulation of external quantum superposition states of BECs.
Stabilization of ring dark solitons in Bose-Einstein condensates
Wang, Wenlong; Kevrekidis, P. G.; Carretero-González, R.; Frantzeskakis, D. J.; Kaper, Tasso J.; Ma, Manjun
2015-09-14
Earlier work has shown that ring dark solitons in two-dimensional Bose-Einstein condensates are generically unstable. In this work, we propose a way of stabilizing the ring dark soliton via a radial Gaussian external potential. We investigate the existence and stability of the ring dark soliton upon variations of the chemical potential and also of the strength of the radial potential. Numerical results show that the ring dark soliton can be stabilized in a suitable interval of external potential strengths and chemical potentials. Furthermore, we also explore different proposed particle pictures considering the ring as a moving particle and find, wheremore » appropriate, results in very good qualitative and also reasonable quantitative agreement with the numerical findings.« less
Stabilization of ring dark solitons in Bose-Einstein condensates
Wang, Wenlong; Kevrekidis, P. G.; Carretero-González, R.; Frantzeskakis, D. J.; Kaper, Tasso J.; Ma, Manjun
2015-09-14
Earlier work has shown that ring dark solitons in two-dimensional Bose-Einstein condensates are generically unstable. In this work, we propose a way of stabilizing the ring dark soliton via a radial Gaussian external potential. We investigate the existence and stability of the ring dark soliton upon variations of the chemical potential and also of the strength of the radial potential. Numerical results show that the ring dark soliton can be stabilized in a suitable interval of external potential strengths and chemical potentials. Furthermore, we also explore different proposed particle pictures considering the ring as a moving particle and find, where appropriate, results in very good qualitative and also reasonable quantitative agreement with the numerical findings.
Scanning Cryogenic Magnetometry with a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Lev, Benjamin; Straquadine, Joshua; Yang, Fan
2016-05-01
Microscopy techniques co-opted from nonlinear optics and high energy physics have complemented solid-state probes in elucidating exotic order manifest in condensed matter systems. We present a novel scanning magnetometer which adds the techniques of ultracold atomic physics to the condensed matter toolbox. Our device, the Scanning Quantum CRyogenic Atom Microscope (SQCRAMscope) uses a one-dimensional Bose-Einstein condensate of 87 Rb to image magnetic and electric fields near surfaces between room and cryogenic temperatures, and allows for rapid sample changes while retaining UHV compatibility for atomic experiments. We present our characterization of the spatial resolution and magnetic field sensitivity of the device, and discuss the advantages and applications of this magnetometry technique. In particular, we will discuss our plans for performing local transport measurements in technologically relevant materials such as Fe-based superconductors and topological insulators.
Quantum turbulence in trapped atomic Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Tsatsos, Marios C.; Tavares, Pedro E. S.; Cidrim, André; Fritsch, Amilson R.; Caracanhas, Mônica A.; dos Santos, F. Ednilson A.; Barenghi, Carlo F.; Bagnato, Vanderlei S.
2016-03-01
Turbulence, the complicated fluid behavior of nonlinear and statistical nature, arises in many physical systems across various disciplines, from tiny laboratory scales to geophysical and astrophysical ones. The notion of turbulence in the quantum world was conceived long ago by Onsager and Feynman, but the occurrence of turbulence in ultracold gases has been studied in the laboratory only very recently. Albeit new as a field, it already offers new paths and perspectives on the problem of turbulence. Herein we review the general properties of quantum gases at ultralow temperatures paying particular attention to vortices, their dynamics and turbulent behavior. We review the recent advances both from theory and experiment. We highlight, moreover, the difficulties of identifying and characterizing turbulence in gaseous Bose-Einstein condensates compared to ordinary turbulence and turbulence in superfluid liquid helium and spotlight future possible directions.
Winding up superfluid in a torus via Bose Einstein condensation
NASA Astrophysics Data System (ADS)
Das, Arnab; Sabbatini, Jacopo; Zurek, Wojciech H.
2012-04-01
Phase transitions are usually treated as equilibrium phenomena, which yields telltale universality classes with scaling behavior of relaxation time and healing length. However, in second-order phase transitions relaxation time diverges near the critical point (``critical slowing down''). Therefore, every such transition traversed at a finite rate is a non-equilibrium process. Kibble-Zurek mechanism (KZM) captures this basic physics, predicting sizes of domains - fragments of broken symmetry - and the density of topological defects, long-lived relics of symmetry breaking that can survive long after the transition. To test KZM we simulate Bose-Einstein condensation in a ring using stochastic Gross-Pitaevskii equation and show that BEC formation can spontaneously generate quantized circulation of the newborn condensate. The magnitude of the resulting winding numbers and the time-lag of BEC density growth - both experimentally measurable - follow scalings predicted by KZM. Our results may also facilitate measuring the dynamical critical exponent for the BEC transition.
Moving impurity in an inhomogenous Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Mathew, Ranchu; Tiesinga, Eite
2016-05-01
We study the dynamics of a non-uniform Bose-Einstein condensate (BEC) under the influence of a moving weak point-like impurity. When the condensate density varies slowly compared to its healing length the critical velocity of the impurity, beyond which the condensate becomes unstable, can be calculated using the Local Density Approximation (LDA). This critical velocity corresponds to the smallest local sound speed. The LDA breaks down when the length scale of density variations is of the order of the healing length. We have calculated corrections to the critical velocity in this regime as an asymptotic expansion in the size of the BEC. We also discuss the experimental implications of our calculations by studying the stability of the atomic analogue of a Superconducting Quantum Interference Device (SQUID). The atom-SQUID consists of a BEC in a ring trap with rotating barrier. The impurity corresponds to imperfections in the ring trap.
Bell correlations in a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Schmied, Roman; Bancal, Jean-Daniel; Allard, Baptiste; Fadel, Matteo; Scarani, Valerio; Treutlein, Philipp; Sangouard, Nicolas
2016-04-01
Characterizing many-body systems through the quantum correlations between their constituent particles is a major goal of quantum physics. Although entanglement is routinely observed in many systems, we report here the detection of stronger correlations—Bell correlations—between the spins of about 480 atoms in a Bose-Einstein condensate. We derive a Bell correlation witness from a many-particle Bell inequality involving only one- and two-body correlation functions. Our measurement on a spin-squeezed state exceeds the threshold for Bell correlations by 3.8 standard deviations. Our work shows that the strongest possible nonclassical correlations are experimentally accessible in many-body systems and that they can be revealed by collective measurements.
Bose-Einstein condensation in liquid 4He under pressure
Glyde, Henry R; Omar Diallo, Souleymane; Azuah, Richard T; Kirichek, Oleg; Taylor, Jon W.
2011-01-01
We present neutron scattering measurements of Bose-Einstein condensation, the atomic momen- tum distribution and Final State effects in liquid 4He under pressure. The condensate fraction at low temperature is found to decrease from n0 = 7.25 0.75% at SVP (p 0) to n0 = 3.2 0.75% at pressure p = 24 bar. This indicates an n0 = 3.0% in the liquid at the liquid/solid co-existence line (p = 25.3 bar). The atomic momentum distribution n(k) has high occupation of low k states and differs significantly from a Gaussian (e.g. a classical n(k)). Both n(k) and the Final state function broaden with increasing pressure, reflecting the increased localization of the 4He in space under increased pressure.
Phonon dispersion relation of an atomic Bose-Einstein condensate.
Shammass, I; Rinott, S; Berkovitz, A; Schley, R; Steinhauer, J
2012-11-01
We measure the time oscillations of a freely evolving standing wave of phonons in a Bose-Einstein condensate. We present the technique of short Bragg pulses, which stimulates the standing wave. The subsequent oscillations are observed in situ. The frequency of the oscillations gives the dispersion relation, the amplitude gives the static structure factor, and the decay gives the dephasing time. The new technique gives orders of magnitude more sensitivity than Bragg spectroscopy, allowing for the observation of deviations from the local density approximation. Specifically, it is seen that the phonons undergo a transition from three dimensions to one dimension, when their wavelength becomes longer than the transverse radius of the condensate. The one-dimensional regime contains an inflection point in the dispersion relation, a decrease in the superfluid critical velocity, a minimum in the group velocity, and an increase in the lifetime of the standing wave oscillations.
Scanning Cryogenic Magnetometry with a 1D Bose Einstein Condensate
NASA Astrophysics Data System (ADS)
Straquadine, Joshua; Yang, Fan; Lev, Benjamin
We present a novel scanning probe magnetometer suitable for cryogenic studies, in which the probe is a Bose-Einstein condensate of 87Rb. The system is designed for rapid sample changes and operation between 35 K and room temperature while remaining compatible with the UHV requirements of ultracold atom experiments. We demonstrate a spatial resolution (FWHM) of 2.6 μm and a repeatability of 1.9 +/- 1.0 nT. We also show that the system is operating close to the fundamental measurement limits set by photon shot noise and atom shot noise. Our scanning quantum cryogenic atom microscope is suitable for fundamental studies of transport and magnetism in condensed matter systems such as high-temperature superconductors and topological insulators. We discuss the advantages and applications of this magnetometry technique.
Momentum-space engineering of gaseous Bose-Einstein condensates
Edwards, Mark; Benton, Brandon; Heward, Jeffrey; Clark, Charles W.
2010-12-15
We show how the momentum distribution of gaseous Bose-Einstein condensates can be shaped by applying a sequence of standing-wave laser pulses. We present a theory, whose validity was demonstrated in an earlier experiment [L. Deng et al., Phys. Rev. Lett. 83, 5407 (1999)], of the effect of a two-pulse sequence on the condensate wavefunction in momentum space. We generalize the previous result to the case of N pulses of arbitrary intensity separated by arbitrary intervals and show how these parameters can be engineered to produce a desired final momentum distribution. We find that several momentum distributions, important in atom-interferometry applications, can be engineered with high fidelity with two or three pulses.
Bose-Einstein condensation in an ultra-hot gas of pumped magnons.
Serga, Alexander A; Tiberkevich, Vasil S; Sandweg, Christian W; Vasyuchka, Vitaliy I; Bozhko, Dmytro A; Chumak, Andrii V; Neumann, Timo; Obry, Björn; Melkov, Gennadii A; Slavin, Andrei N; Hillebrands, Burkard
2014-03-11
Bose-Einstein condensation of quasi-particles such as excitons, polaritons, magnons and photons is a fascinating quantum mechanical phenomenon. Unlike the Bose-Einstein condensation of real particles (like atoms), these processes do not require low temperatures, since the high densities of low-energy quasi-particles needed for the condensate to form can be produced via external pumping. Here we demonstrate that such a pumping can create remarkably high effective temperatures in a narrow spectral region of the lowest energy states in a magnon gas, resulting in strikingly unexpected transitional dynamics of Bose-Einstein magnon condensate: the density of the condensate increases immediately after the external magnon flow is switched off and initially decreases if it is switched on again. This behaviour finds explanation in a nonlinear 'evaporative supercooling' mechanism that couples the low-energy magnons overheated by pumping with all the other thermal magnons, removing the excess heat, and allowing Bose-Einstein condensate formation.
Two characteristic temperatures for a Bose-Einstein condensate of a finite number of particles
Idziaszek, Z.; Rzazewski, K.
2003-09-01
We consider two characteristic temperatures for a Bose-Einstein condensate, which are related to certain properties of the condensate statistics. We calculate them for an ideal gas confined in power-law traps and show that they approach the critical temperature in the limit of large number of particles. The considered characteristic temperatures can be useful in the studies of Bose-Einstein condensates of a finite number of atoms indicating the point of a phase transition.
NASA Astrophysics Data System (ADS)
Deng, Hai-Ming; Zhong, Hong-Hua; Huang, Jia-Hao; Dai, Hui; Yao, Min; Huang, Xiao-Yi
2015-08-01
We investigate modulational instability (MI) of a coupled two-component Bose-Einstein condensates in a rotating ring trap. The excitation spectrum and the MI condition of the system are presented analytically. We find that the coupling between the two components strongly modifies the MI condition, and the MI condition is phase-dependent. Furthermore, we discuss the effect of MI on both density excitation and spin excitation. If the inter- and intra-component interaction strengths are all equal, the MI causes density excitation but not spin excitation, and if the inter- and intra-component interaction strengths are different, the MI causes both density excitation and spin excitation. Our results provide a promising approach for controlling the stability and excitation of a rotating two-component Bose-Einstein condensates by modulating its coupling strength and interaction strength. Supported by the National Natural Science Foundation of China under Grant No. 11465008, the Hunan Provincial Natural Science Foundation under Grant No. 2015JJ2114, the Scientific Research Fund of Hunan Provincial Education Department under Grant Nos. 14A118, 13C881, Science and Technology Innovative Research Team in Higher Educational Instituions of Hunan Province, and Science Research Foundation of Xiangnan University under Grant No. 2012-126(41)
Solitons and solitary vortices in pancake-shaped Bose-Einstein condensates
Salasnich, Luca; Malomed, Boris A.
2009-05-15
We study fundamental and vortical solitons in disk-morphed Bose-Einstein condensates (BECs) subject to strong confinement along the axial direction. Starting from the three-dimensional (3D) Gross-Pitaevskii equation (GPE), we proceed to an effective two-dimensional (2D) nonpolynomial Schroedinger equation (NPSE) derived by means of the integration over the axial coordinate. Results produced by the latter equation are in very good agreement with those obtained from the full 3D GPE, including cases when the formal 2D equation with the cubic nonlinearity is unreliable. The 2D NPSE is used to predict the density profiles and dynamical stability of repulsive and attractive BECs with zero and finite topological charges in various planar trapping configurations, including the axisymmetric harmonic confinement and one-dimensional periodic potential. In particular, we find a stable dynamical regime that was not reported before, viz., periodic splitting and recombination of trapped vortices with topological charges 2 or 3 in the self-attractive BEC.
NASA Astrophysics Data System (ADS)
Mikhaylov, Konstantin
2016-01-01
Due to the effects of quantum statistics and final state interactions, momentum correlations of two or more particles at small relative velocities, i.e. at small relative momenta in their center-of-mass system, are sensitive to the space-time characteristics of the production processes at the level of fm (10-15 m). Kaons are the perfect tool to study Bose-Einstein correlations due to the fact that they are less influenced by resonance decays and therefore probe more effectively directly produced particles. In conjunction with femtoscopic measurements of pions and protons, they can also reveal properties of collective dynamics in heavy-ion collisions. We report on the results of Bose-Einstein correlations of charged and neutral kaons in pp collisions at√s = 7 TeV and in Pb-Pb collisions at √sNN = 2.76 TeV by the ALICE experiment at the LHC. The results are compared with existing data from Bose-Einstein correlations of identical pions at LHC energies, and of kaons in pp collisions. A comparison of experimental data with theoretical expectations is also carried out.
Defect matter-wave gap solitons in spin-orbit-coupled Bose-Einstein condensates in Zeeman lattices
NASA Astrophysics Data System (ADS)
Zhu, Xing; Li, Huagang; Shi, Zhiwei
2016-09-01
We report on the properties of fundamental defect matter-wave gap solitons in spin-orbit-coupled Bose-Einstein condensates in one-dimensional Zeeman lattices with attractive nonlinearity. One component of these solitons is a real even function, and the other is an imaginary odd function. When the defect is repulsive, these solitons can be stable in the semi-infinite, first, and second gaps. Increasing the strength of spin-orbit coupling, stable defect gap-stripe solitons in the semi-infinite and first gaps are found. However, for an attractive defect, the solitons only stably exist in the semi-infinite gap and cannot be close to the lower edge of the first Bloch band.
Dynamics of three noncorotating vortices in Bose-Einstein condensates.
Koukouloyannis, V; Voyatzis, G; Kevrekidis, P G
2014-04-01
In this work we use standard Hamiltonian-system techniques in order to study the dynamics of three vortices with alternating charges in a confined Bose-Einstein condensate. In addition to being motivated by recent experiments, this system offers a natural vehicle for the exploration of the transition of the vortex dynamics from ordered to progressively chaotic behavior. In particular, it possesses two integrals of motion, the energy (which is expressed through the Hamiltonian H) and the angular momentum L of the system. By using the integral of the angular momentum, we reduce the system to a 2-degrees-of-freedom one with L as a parameter and reveal the topology of the phase space through the method of Poincaré surfaces of section. We categorize the various motions that appear in the different regions of the sections and we study the major bifurcations that occur to the families of periodic motions of the system. Finally, we correspond the orbits on the surfaces of section to the real space motion of the vortices in the plane.
Subsonic and Supersonic Effects in Bose-Einstein Condensate
NASA Technical Reports Server (NTRS)
Zak, Michail
2003-01-01
A paper presents a theoretical investigation of subsonic and supersonic effects in a Bose-Einstein condensate (BEC). The BEC is represented by a time-dependent, nonlinear Schroedinger equation that includes terms for an external confining potential term and a weak interatomic repulsive potential proportional to the number density of atoms. From this model are derived Madelung equations, which relate the quantum phase with the number density, and which are used to represent excitations propagating through the BEC. These equations are shown to be analogous to the classical equations of flow of an inviscid, compressible fluid characterized by a speed of sound (g/Po)1/2, where g is the coefficient of the repulsive potential and Po is the unperturbed mass density of the BEC. The equations are used to study the effects of a region of perturbation moving through the BEC. The excitations created by a perturbation moving at subsonic speed are found to be described by a Laplace equation and to propagate at infinite speed. For a supersonically moving perturbation, the excitations are found to be described by a wave equation and to propagate at finite speed inside a Mach cone.
Stagflation: Bose-Einstein condensation in the early universe
NASA Astrophysics Data System (ADS)
Fukuyama, Takeshi; Morikawa, Masahiro
2009-09-01
Our universe experienced the accelerated expansion at least twice; an extreme inflationary acceleration in the early universe and the recent mild acceleration. By introducing the Bose-Einstein condensation (BEC) phase of a boson field, we have been developing a unified model of dark energy (DE) and dark matter (DM) for the later mild acceleration. In this scenario, two phases of BEC (=DE) and normal gas (=DM) transform with each other through BEC phase transition. This unified model has successfully explained the mild acceleration as an attractor. We extend this BEC cosmology to the early universe without introducing new ingredients. In this scenario, the inflation is naturally initiated by the condensation of the bosons in the huge vacuum energy. This inflation and even the cosmic expansion eventually terminates exactly at zero energy density. We call this stage as stagflation. At this stagflation era, particle production and the decay of BEC take place. The former makes the universe turn into the standard hot big bang stage and the latter makes the cosmological constant vanishingly small after the inflation. Furthermore, we calculate the density fluctuations produced in this model, which turns out to be in the range allowed by the present observational data. We also show that the stagflation is quite robust and easily appears when one allows negative region of the potential. Further, we comment on the possibility that BEC generation/decay series might have continued all the time in the cosmic history from the inflation to present.
Recent experiments with ring Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Eckel, S.; Kumar, A.; Anderson, N. W.; Campbell, G. K.
2016-05-01
Here, we present three recent results of our experiments with ring-shaped 23 Na Bose-Einstein condensates. First, we present results of the effect of temperature on the decay of persistent currents in the presence of a local, stationary perturbation, or weak link. When the weak link rotates, it can drive transitions between quantized persistent current states in the ring, that form hysteresis loops whose size depends strongly on temperature. We find that our data does not fit with a simple model of thermal activation. Second, we present a new method to measure the quantized persistent current state of the ring in a minimally-destructive way. This technique uses phonons as probes of the background flow through the Doppler effect. Finally, we present a set of experiments designed to reproduce the horizon problem in the early universe. Supersonic expansion of the ring creates causally-disconnected regions of BEC whose phase evolves at different rates. When the expansion stops and these regions are allowed to recombine, they form topological excitations. These excitations can be predicted using a simple theory that shows excellent agreement with the data.
Geometric ``charge'' pumping with a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Spielman, Ian
We realized a quantum ''charge'' pump for a Bose-Einstein condensate (BEC) in a novel bipartite magnetic lattice, whose bands are characterized by non-trivial topological invariants: the Zak phases. For each band, the Zak phase is determined by that band's integrated Berry curvature, a geometric quantity defined at each crystal momentum. We probed this Berry curvature in a charge pump experiment, by periodically and adiabatically driving the system. Unlike topological charge pumps in filled bands that yield quantized pumping, our BEC occupied just a single crystal momentum state allowing us to access its band's local geometry. Like topological charge pumps, for each pump cycle we observed an overall displacement (here, not quantized) and a temporal modulation of the atomic wavepacket's position in each unit cell, i.e., the polarization. Our magnetic lattice enabled us to observe this modulation by measuring the BEC's magnetization. While our periodic drive shifted the lattice potential by one unit cell per cycle, the displacement of the BEC, solely determined by the underlying Berry curvature, was always less than the lattice's displacement.
Bose-Einstein condensation in low dimensional layered structures
NASA Astrophysics Data System (ADS)
Salas, Patricia; Solis, M. A.
2008-03-01
Bose-Einstein condensation critical temperature, among other thermodynamic properties are reported for an ideal boson gas inside layered structures created by trapping potential of the Kronig-Penney type. We start with a big box where we introduce the Kronig-Penney potential in three directions to get a honey comb of cubes of side a size and walls of variable penetrability (P=mV0ab/^2), with bosons instead of bees. We are able to reduce the dimensions of the cubes to simulate bosons inside quantum dots. The critical temperature, starting from that of an ideal boson gas inside the big box, decreases as the small cube wall impenetrability increases arriving to a tiny but different from zero when the penetrability is zero (P-->∞). We also calculate the internal energy and the specific heat, and compare them to the ones obtained for the case of the same Kronig-Penney potential in one direction (simulating layers), and two directions (nanotubes).
Atom loss resonances in a Bose-Einstein condensate.
Langmack, Christian; Smith, D Hudson; Braaten, Eric
2013-07-12
Atom loss resonances in ultracold trapped atoms have been observed at scattering lengths near atom-dimer resonances, at which Efimov trimers cross the atom-dimer threshold, and near two-dimer resonances, at which universal tetramers cross the dimer-dimer threshold. We propose a new mechanism for these loss resonances in a Bose-Einstein condensate of atoms. As the scattering length is ramped to the large final value at which the atom loss rate is measured, the time-dependent scattering length generates a small condensate of shallow dimers coherently from the atom condensate. The coexisting atom and dimer condensates can be described by a low-energy effective field theory with universal coefficients that are determined by matching exact results from few-body physics. The classical field equations for the atom and dimer condensates predict narrow enhancements in the atom loss rate near atom-dimer resonances and near two-dimer resonances due to inelastic dimer collisions.
Winding up superfluid in a torus via Bose Einstein condensation
Das, Arnab; Sabbatini, Jacopo; Zurek, Wojciech H.
2012-01-01
Phase transitions are usually treated as equilibrium phenomena, which yields telltale universality classes with scaling behavior of relaxation time and healing length. However, in second-order phase transitions relaxation time diverges near the critical point (“critical slowing down”). Therefore, every such transition traversed at a finite rate is a non-equilibrium process. Kibble-Zurek mechanism (KZM) captures this basic physics, predicting sizes of domains – fragments of broken symmetry – and the density of topological defects, long-lived relics of symmetry breaking that can survive long after the transition. To test KZM we simulate Bose-Einstein condensation in a ring using stochastic Gross-Pitaevskii equation and show that BEC formation can spontaneously generate quantized circulation of the newborn condensate. The magnitude of the resulting winding numbers and the time-lag of BEC density growth – both experimentally measurable – follow scalings predicted by KZM. Our results may also facilitate measuring the dynamical critical exponent for the BEC transition. PMID:22500209
Generating, dragging, and releasing dark solitons in elongated Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Hans, I.; Stockhofe, J.; Schmelcher, P.
2015-07-01
We theoretically analyze quasi-one-dimensional Bose-Einstein condensates under the influence of a harmonic trap and a narrow potential defect that moves through the atomic cloud. Performing simulations on the mean-field level, we explore a robust mechanism in which a single dark soliton is nucleated and immediately pinned by the moving defect, making it possible to drag it to a desired position and release it there. We argue on a perturbative level that a defect potential which is attractive to the atoms is suitable for holding and moving dark solitons. The soliton generation protocol is investigated over a wide range of model parameters and its success is systematically quantified by a suitable fidelity measure, demonstrating its robustness against parameter variations, but also the need for tight focusing of the defect potential. Holding the soliton at a stationary defect for long times may give rise to dynamical instabilities, whose origin we explore within a Bogoliubov-de Gennes linearization analysis. We show that iterating the generation process with multiple defects offers a perspective for initializing multiple soliton dynamics with freely chosen initial conditions.
Elements of Vortex-Dipole Dynamics in a Nonuniform Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Sakhel, Roger R.; Sakhel, Asaad R.
2016-09-01
The elements of the vortex-dipole (VD) dynamics are numerically examined in a nonuniform Bose-Einstein condensate (BEC) using the time-dependent Gross-Pitaevskii equation that is solved by the split-step Crank-Nicolson method in real time. The BEC is trapped in a harmonic potential, surrounded by a hard-wall box potential, and stirred by an attractive focusing laser. In this regard, we particularly refer to a recent examination by Aioi et al. (Phys. Rev. X, 1: 021003, 2011) who presented controlled VD generation using a red laser in an infinite homogeneous BEC for comparison. It is found that the dynamics in the present nonuniform BEC is quite different from the one reported earlier by Aioi et al. The elements considered are the phase maps that demonstrate the presence of phase rings, the effects of the coupling constant on the vortex lifetime, the density at the vortex core, and the heating effects of the stirrer. Upon a suitable choice of coupling for our system, a VD generated by the moving fragment is transferred to and trapped by the central BEC cloud. The latter serves as a dissipationless vortex respository, where the lifetime of the VD is extended on demand. An analytical model is presented that qualitatively reproduces the wavefunction with its principle features and provides details inaccessible by the present numerical method such as the coupling between stirrer and BEC.
Tunable Polarons of Slow-Light Polaritons in a Two-Dimensional Bose-Einstein Condensate.
Grusdt, Fabian; Fleischhauer, Michael
2016-02-01
When an impurity interacts with a bath of phonons it forms a polaron. For increasing interaction strengths the mass of the polaron increases and it can become self-trapped. For impurity atoms inside an atomic Bose-Einstein condensate (BEC) the nature of this transition is not understood. While Feynman's variational approach to the Fröhlich model predicts a sharp transition for light impurities, renormalization group studies always predict an extended intermediate-coupling region characterized by large phonon correlations. To investigate this intricate regime and to test polaron physics beyond the validity of the Fröhlich model we suggest a versatile experimental setup that allows us to tune both the mass of the impurity and its interactions with the BEC. The impurity is realized as a dark-state polariton (DSP) inside a quasi-two-dimensional BEC. We show that its interactions with the Bogoliubov phonons lead to photonic polarons, described by the Bogoliubov-Fröhlich Hamiltonian, and make theoretical predictions using an extension of a recently introduced renormalization group approach to Fröhlich polarons. PMID:26894712
Tunable Polarons of Slow-Light Polaritons in a Two-Dimensional Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Grusdt, Fabian; Fleischhauer, Michael
2016-02-01
When an impurity interacts with a bath of phonons it forms a polaron. For increasing interaction strengths the mass of the polaron increases and it can become self-trapped. For impurity atoms inside an atomic Bose-Einstein condensate (BEC) the nature of this transition is not understood. While Feynman's variational approach to the Fröhlich model predicts a sharp transition for light impurities, renormalization group studies always predict an extended intermediate-coupling region characterized by large phonon correlations. To investigate this intricate regime and to test polaron physics beyond the validity of the Fröhlich model we suggest a versatile experimental setup that allows us to tune both the mass of the impurity and its interactions with the BEC. The impurity is realized as a dark-state polariton (DSP) inside a quasi-two-dimensional BEC. We show that its interactions with the Bogoliubov phonons lead to photonic polarons, described by the Bogoliubov-Fröhlich Hamiltonian, and make theoretical predictions using an extension of a recently introduced renormalization group approach to Fröhlich polarons.
Tunable Polarons of Slow-Light Polaritons in a Two-Dimensional Bose-Einstein Condensate.
Grusdt, Fabian; Fleischhauer, Michael
2016-02-01
When an impurity interacts with a bath of phonons it forms a polaron. For increasing interaction strengths the mass of the polaron increases and it can become self-trapped. For impurity atoms inside an atomic Bose-Einstein condensate (BEC) the nature of this transition is not understood. While Feynman's variational approach to the Fröhlich model predicts a sharp transition for light impurities, renormalization group studies always predict an extended intermediate-coupling region characterized by large phonon correlations. To investigate this intricate regime and to test polaron physics beyond the validity of the Fröhlich model we suggest a versatile experimental setup that allows us to tune both the mass of the impurity and its interactions with the BEC. The impurity is realized as a dark-state polariton (DSP) inside a quasi-two-dimensional BEC. We show that its interactions with the Bogoliubov phonons lead to photonic polarons, described by the Bogoliubov-Fröhlich Hamiltonian, and make theoretical predictions using an extension of a recently introduced renormalization group approach to Fröhlich polarons.
Melting of phase-stripes in Bose-Einstein condensates with synthetic spin-orbit coupling
NASA Astrophysics Data System (ADS)
Sudbo, Asle; Galteland, Peder; Babaev, Egor
We study a two-component, density imbalanced Bose-Einstein condensate with density-density interactions and synthetic spin-orbit coupling, focusing on the impact of thermal fluctuations and density-density interactions on spin-orbit induced effects. We find that for intermediate density imbalance and small intercomponent density-density interactions, the ground state is non-uniform, represented by a striped state of modulated phases of the individual complex order parameter components. By using mean-field stability arguments, we calculate a critical value for the intercomponent density-density interaction, above which the non-uniform ground state collapses into a uniform single-component state. This is reproduced in Monte-Carlo simulations for intermediate values of the spin-orbit coupling. We also find that the non-uniform ground state is disordered by thermal fluctuations when heated, through a Berizinskii-Kosterlitz-Thouless unbinding of disclocation pairs. We argue that, to lowest order, the spin-orbit coupling can be seen as an effective Josephson-type locking of the phase difference θ1 -θ2 while simultaneously allowing the system to gain energy by modulating the phase sum θ1 +θ2 . Work supported by the Norwegian Research Council, the Swedish Research Council, and the National Science Foundation.
Cuprate superconductors. Universal properties and trends; evidence for Bose-Einstein condensation
Schneider, T.; Pedersen, M.H. )
1994-06-01
We explore the compatibility of empirical trends in various thermodynamic properties of cuprate superconductors with the Bose-Einstein condensation scenario. These trends include the relations between transition temperature, hole concentration and condensate density, the rise and the upper limit of the transition temperature, the dependence of pressure and isotope coefficients on transition temperature, as well as the observed critical behavior, which is reminiscent of three-dimensional systems with a scalar complex order parameter and short-range interactions. For this purpose we consider an interacting charged Bose gas. Due to the high polarizability of the cuprates, the Coulomb interaction is strongly screened. For this reason, the problem of calculating thermodynamic properties becomes essentially equivalent to that of the uncharged gas with short-range interactions. This problem, however, has not been solved either. Nevertheless, in the dilute limit the problem reduces to the ideal Bose gas treated by Schafroth, while in the dense regime condensation and superfluidity are suppressed because bosons of finite extension fill the available volume. This limiting behavior provides an interpolation scheme for the dependence of both transition temperature and zero temperature superfluid density on boson density. 23 refs., 5 figs.
Energy Band and Josephson Dynamics of Spin-Orbit Coupled Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Zhang, Xin; Yu, Zi-Fa; Xue, Ju-Kui
2015-10-01
We theoretically investigate the energy band structure and Josephson dynamics of a spin-orbit coupled Bose-Einstein condensate in a double-well potential. We study the energy band structure and the corresponding tunneling dynamics of the system by properly adjusting the SO coupling, Raman coupling, Zeeman field and atomic interactions. The coupled effects of SO coupling, Raman coupling, Zeeman field and atomic interactions lead to the appearance of complex energy band structure including the loop structure. Particularly, the emergence of the loop structure in energy band also depends on SO coupling, Raman coupling, Zeeman field and atomic interactions. Correspondingly, the Josephson dynamics of the system are strongly related to the energy band structure. Especially, the emergence of the loop structure results in complex tunneling dynamics, including suppression-revival transitions and self-trapping of atoms transfer between two spin states and two wells. This engineering provides a possible means for studying energy level and corresponding dynamics of two-species SO coupled BECs. Supported by the National Natural Science Foundation of China under Grant Nos. 11274255 and 11305132, by Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20136203110001, by the Natural Science Foundation of Gansu province under Grant No. 2011GS04358, and by Creation of Science and Technology of Northwest Normal University under Grant Nos. NWNU-KJCXGC-03-48, NWNU-LKQN-12-12
Collective dynamics of a spin-orbit-coupled Bose-Einstein condensate.
Hu, Fang-Qi; Wang, Jian-Jun; Yu, Zi-Fa; Zhang, Ai-Xia; Xue, Ju-Kui
2016-02-01
We study the collective dynamics of the spin-orbit coupled two pseudospin components of a Bose-Einstein condensate trapped in a quasi-one-dimensional harmonic potential, by using variational and directly numerical approach of binary mean-field Gross-Pitaevskii equations. The results show that, because of strong coupling of spin-orbit coupling (SOC), Rabi coupling, and atomic interaction, the collective dynamics of the system behave as complex characters. When the Rabi coupling is absent, the density profiles of the system preserve the Gauss type and the wave packets do harmonic oscillations. The amplitude of the collective oscillations increases with SOC. Furthermore, when the SOC strength increases, the dipole oscillations of the two pseudospin components undergo a transition from in-phase to out-of-phase oscillations. When the Rabi coupling present, there will exist a critical value of SOC strength (which depends on the Rabi coupling and atomic interaction). If the SOC strength is less than this critical value, the density profiles of the system can preserve the Gauss type and the wave packets do anharmonic (the frequency of dipole oscillations depends on SOC) oscillations synchronously (i.e., in-phase oscillations). However, if the SOC strength is larger than this critical value, the wave packets are dynamically fragmented and the stable dipole oscillations of the system can not exist. The collective dynamics of the system can be controlled by adjusting the atomic interaction, SOC, and Rabi-coupling strength.
Collective dynamics of a spin-orbit-coupled Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Hu, Fang-Qi; Wang, Jian-Jun; Yu, Zi-Fa; Zhang, Ai-Xia; Xue, Ju-Kui
2016-02-01
We study the collective dynamics of the spin-orbit coupled two pseudospin components of a Bose-Einstein condensate trapped in a quasi-one-dimensional harmonic potential, by using variational and directly numerical approach of binary mean-field Gross-Pitaevskii equations. The results show that, because of strong coupling of spin-orbit coupling (SOC), Rabi coupling, and atomic interaction, the collective dynamics of the system behave as complex characters. When the Rabi coupling is absent, the density profiles of the system preserve the Gauss type and the wave packets do harmonic oscillations. The amplitude of the collective oscillations increases with SOC. Furthermore, when the SOC strength increases, the dipole oscillations of the two pseudospin components undergo a transition from in-phase to out-of-phase oscillations. When the Rabi coupling present, there will exist a critical value of SOC strength (which depends on the Rabi coupling and atomic interaction). If the SOC strength is less than this critical value, the density profiles of the system can preserve the Gauss type and the wave packets do anharmonic (the frequency of dipole oscillations depends on SOC) oscillations synchronously (i.e., in-phase oscillations). However, if the SOC strength is larger than this critical value, the wave packets are dynamically fragmented and the stable dipole oscillations of the system can not exist. The collective dynamics of the system can be controlled by adjusting the atomic interaction, SOC, and Rabi-coupling strength.
Dynamics of a macroscopic spin qubit in spin-orbit coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Mardonov, Sh; Modugno, M.; Sherman, E. Ya
2015-06-01
We consider a macroscopic spin qubit based on spin-orbit coupled Bose-Einstein condensates, where, in addition to the spin-orbit coupling (SOC), spin dynamics strongly depends on the interaction between particles. The evolution of the spin for freely expanding, trapped, and externally driven condensates is investigated. For condensates oscillating at the frequency corresponding to the Zeeman splitting in the synthetic magnetic field, the spin Rabi frequency does not depend on the interaction between the atoms since it produces only internal forces and does not change the total momentum. However, interactions and SOC bring the system into a mixed spin state, where the total spin is inside rather than on the Bloch sphere. This greatly extends the available spin space making it three-dimensional, but imposes limitations on the reliable spin manipulation of such a macroscopic qubit. The spin dynamics can be modified by introducing suitable spin-dependent initial phases, determined by the SOC, in the spinor wave function.
Trap- and population-imbalanced two-component Fermi gas in the Bose-Einstein-condensate limit
Silotri, S. A.
2010-01-15
We study equal mass population imbalanced two-component atomic Fermi gas with unequal trap frequencies (omega{sub a}rrow upnot =omega{sub a}rrow down) at zero temperature using the local density approximation (LDA). We consider the strongly attracting Bose-Einstein condensation (BEC) limit where polarized (gapless) superfluid is stable. The system exhibits shell structure: unpolarized superfluid->polarized superfluid->normal state. Compared to the trap symmetric case, when the majority component is tightly confined the gapless superfluid shell grows in size leading to reduced threshold polarization to form a polarized (gapless) superfluid core. In contrast, when the minority component is tightly confined, we find that the superfluid phase is dominated by the unpolarized superfluid phase with the gapless phase forming a narrow shell. The shell radii for various phases as a function of polarization at different values of trap asymmetry are presented and the features are explained using the phase diagram.
Cosmological perturbations during the Bose-Einstein condensation of dark matter
Freitas, R.C.; Gonçalves, S.V.B. E-mail: sergio.vitorino@pq.cnpq.br
2013-04-01
In the present work, we analyze the evolution of the scalar and tensorial perturbations and the quantities relevant for the physical description of the Universe, as the density contrast of the scalar perturbations and the gravitational waves energy density during the Bose-Einstein condensation of dark matter. The behavior of these parameters during the Bose-Einstein phase transition of dark matter is analyzed in details. To study the cosmological dynamics and evolution of scalar and tensorial perturbations in a Universe with and without cosmological constant we use both analytical and numerical methods. The Bose-Einstein phase transition modifies the evolution of gravitational waves of cosmological origin, as well as the process of large-scale structure formation.
Hidden vortices in a Bose-Einstein condensate in a rotating double-well potential
Wen Linghua; Xiong Hongwei; Wu Biao
2010-11-15
We study vortex formation in a Bose-Einstein condensate in a rotating double-well potential. In addition to the ordinary quantized vortices and elusive ghost vortices, 'hidden' vortices are found distributed along the central barrier. These hidden vortices are invisible like ghost vortices but carry angular momentum. Moreover, their core size is not given by the healing length, but is strongly influenced by the external potential. We find that the Feynman rule can be well satisfied only after including the hidden vortices. There is no critical rotation frequency for the formation of hidden vortices while there is one for the formation of ordinary visible vortices. Hidden vortices can be revealed in the free expansion of Bose-Einstein condensates. In addition, the hidden vortices in a Bose-Einstein condensate can appear in other external potentials, such as a rotating anisotropic toroidal trap.
Thermalization and Bose-Einstein condensation of quantum light in bulk nonlinear media
NASA Astrophysics Data System (ADS)
Chiocchetta, A.; Larré, P.-É.; Carusotto, I.
2016-07-01
We study the thermalization and the Bose-Einstein condensation of a paraxial, spectrally narrow beam of quantum light propagating in a lossless bulk Kerr medium. The spatiotemporal evolution of the quantum optical field is ruled by a Heisenberg equation analogous to the quantum nonlinear Schrödinger equation of dilute atomic Bose gases. Correspondingly, in the weak-nonlinearity regime, the phase-space density evolves according to the Boltzmann equation. Expressions for the thermalization time and for the temperature and the chemical potential of the eventual Bose-Einstein distribution are found. After discussing experimental issues, we introduce an optical setup allowing the evaporative cooling of a guided beam of light towards Bose-Einstein condensation. This might serve as a novel source of coherent light.
Homogeneous one-dimensional Bose-Einstein condensate in the Bogoliubov’s regime
NASA Astrophysics Data System (ADS)
Castellanos, Elías
2016-08-01
We analyze the corrections caused by finite size effects upon the ground state properties of a homogeneous one-dimensional (1D) Bose-Einstein condensate. We assume from the very beginning that the Bogoliubov’s formalism is valid and consequently, we show that in order to obtain a well-defined ground state properties, finite size effects of the system must be taken into account. Indeed, the formalism described in the present paper allows to recover the usual properties related to the ground state of a homogeneous 1D Bose-Einstein condensate but corrected by finite size effects of the system. Finally, this scenario allows us to analyze the sensitivity of the system when the Bogoliubov’s regime is valid and when finite size effects are present. These facts open the possibility to apply these ideas to more realistic scenarios, e.g. low-dimensional trapped Bose-Einstein condensates.
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
Phase separation and dynamics of two-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Lee, Kean Loon; Jørgensen, Nils B.; Liu, I.-Kang; Wacker, Lars; Arlt, Jan J.; Proukakis, Nick P.
2016-07-01
The miscibility of two interacting quantum systems is an important testing ground for the understanding of complex quantum systems. Two-component Bose-Einstein condensates enable the investigation of this scenario in a particularly well controlled setting. In a homogeneous system, the transition between mixed and separated phases is fully characterized by a miscibility parameter based on the ratio of intra- to interspecies interaction strengths. Here we show, however, that this parameter is no longer the optimal one for trapped gases, for which the location of the phase boundary depends critically on atom numbers. We demonstrate how monitoring of damping rates and frequencies of dipole oscillations enables the experimental mapping of the phase diagram by numerical implementation of a fully self-consistent finite-temperature kinetic theory for binary condensates. The change in damping rate is explained in terms of surface oscillation in the immiscible regime, and counterflow instability in the miscible regime, with collisions becoming only important in the long time evolution.
Two-component dipolar Bose-Einstein condensate in concentrically coupled annular traps
Zhang, Xiao-Fei; Han, Wei; Wen, Lin; Zhang, Peng; Dong, Rui-Fang; Chang, Hong; Zhang, Shou-Gang
2015-01-01
Dipolar Bosonic atoms confined in external potentials open up new avenues for quantum-state manipulation and will contribute to the design and exploration of novel functional materials. Here we investigate the ground-state and rotational properties of a rotating two-component dipolar Bose-Einstein condensate, which consists of both dipolar bosonic atoms with magnetic dipole moments aligned vertically to the condensate and one without dipole moments, confined in concentrically coupled annular traps. For the nonrotational case, it is found that the tunable dipolar interaction can be used to control the location of each component between the inner and outer rings, and to induce the desired ground-state phase. Under finite rotation, it is shown that there exists a critical value of rotational frequency for the nondipolar case, above which vortex state can form at the trap center, and the related vortex structures depend strongly on the rotational frequency. For the dipolar case, it is found that various ground-state phases and the related vortex structures, such as polygonal vortex clusters and vortex necklaces, can be obtained via a proper choice of the dipolar interaction and rotational frequency. Finally, we also study and discuss the formation process of such vortex structures. PMID:25731962
Orbit-induced spin squeezing in a spin-orbit coupled Bose-Einstein condensate
Lian, Jinling; Yu, Lixian; Liang, J.-Q.; Chen, Gang; Jia, Suotang
2013-01-01
In recent pioneer experiment, a strong spin-orbit coupling, with equal Rashba and Dresselhaus strengths, has been created in a trapped Bose-Einstein condensate. Moreover, many exotic superfluid phenomena induced by this strong spin-orbit coupling have been predicted. In this report, we show that this novel spin-orbit coupling has important applications in quantum metrology, such as spin squeezing. We first demonstrate that an effective spin-spin interaction, which is the heart for producing spin squeezing, can be generated by controlling the orbital degree of freedom (i.e., the momentum) of the ultracold atoms. Compared with previous schemes, this realized spin-spin interaction has advantages of no dissipation, high tunability, and strong coupling. More importantly, a giant squeezing factor (lower than −30 dB) can be achieved by tuning a pair of Raman lasers in current experimental setup. Finally, we find numerically that the phase factor of the prepared initial state affects dramatically on spin squeezing. PMID:24196590
Two-component dipolar Bose-Einstein condensate in concentrically coupled annular traps
NASA Astrophysics Data System (ADS)
Zhang, Xiao-Fei; Han, Wei; Wen, Lin; Zhang, Peng; Dong, Rui-Fang; Chang, Hong; Zhang, Shou-Gang
2015-03-01
Dipolar Bosonic atoms confined in external potentials open up new avenues for quantum-state manipulation and will contribute to the design and exploration of novel functional materials. Here we investigate the ground-state and rotational properties of a rotating two-component dipolar Bose-Einstein condensate, which consists of both dipolar bosonic atoms with magnetic dipole moments aligned vertically to the condensate and one without dipole moments, confined in concentrically coupled annular traps. For the nonrotational case, it is found that the tunable dipolar interaction can be used to control the location of each component between the inner and outer rings, and to induce the desired ground-state phase. Under finite rotation, it is shown that there exists a critical value of rotational frequency for the nondipolar case, above which vortex state can form at the trap center, and the related vortex structures depend strongly on the rotational frequency. For the dipolar case, it is found that various ground-state phases and the related vortex structures, such as polygonal vortex clusters and vortex necklaces, can be obtained via a proper choice of the dipolar interaction and rotational frequency. Finally, we also study and discuss the formation process of such vortex structures.
Rashba-type spin-orbit coupling in bilayer Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Su, S.-W.; Gou, S.-C.; Sun, Q.; Wen, L.; Liu, W.-M.; Ji, A.-C.; Ruseckas, J.; JuzeliÅ«nas, G.
2016-05-01
We explore a way of producing the Rashba spin-orbit coupling (SOC) for ultracold atoms by using a two-component (spinor) atomic Bose-Einstein condensate (BEC) confined in a bilayer geometry. The SOC of the Rashba type is created if the atoms pick up a π phase after completing a cyclic transition between four combined spin-layer states composed of two spin and two layer states. The cyclic coupling of the spin-layer states is carried out by combining an intralayer Raman coupling and an interlayer laser assisted tunneling. We theoretically determine the ground-state phases of the spin-orbit-coupled BEC for various strengths of the atom-atom interaction and the laser-assisted coupling. It is shown that the bilayer scheme provides a diverse ground-state phase diagram. In an intermediate range of the atom-light coupling two interlacing lattices of half-skyrmions and half-antiskyrmions are spontaneously created. In the strong-coupling regime, where the SOC of the Rashba type is formed, the ground state represents plane-wave or standing-wave phases depending on the interaction between the atoms. A variational analysis is shown to be in good agreement with the numerical results.
Two-component dipolar Bose-Einstein condensate in concentrically coupled annular traps.
Zhang, Xiao-Fei; Han, Wei; Wen, Lin; Zhang, Peng; Dong, Rui-Fang; Chang, Hong; Zhang, Shou-Gang
2015-03-03
Dipolar Bosonic atoms confined in external potentials open up new avenues for quantum-state manipulation and will contribute to the design and exploration of novel functional materials. Here we investigate the ground-state and rotational properties of a rotating two-component dipolar Bose-Einstein condensate, which consists of both dipolar bosonic atoms with magnetic dipole moments aligned vertically to the condensate and one without dipole moments, confined in concentrically coupled annular traps. For the nonrotational case, it is found that the tunable dipolar interaction can be used to control the location of each component between the inner and outer rings, and to induce the desired ground-state phase. Under finite rotation, it is shown that there exists a critical value of rotational frequency for the nondipolar case, above which vortex state can form at the trap center, and the related vortex structures depend strongly on the rotational frequency. For the dipolar case, it is found that various ground-state phases and the related vortex structures, such as polygonal vortex clusters and vortex necklaces, can be obtained via a proper choice of the dipolar interaction and rotational frequency. Finally, we also study and discuss the formation process of such vortex structures.
Orbit-induced spin squeezing in a spin-orbit coupled Bose-Einstein condensate.
Lian, Jinling; Yu, Lixian; Liang, J-Q; Chen, Gang; Jia, Suotang
2013-11-07
In recent pioneer experiment, a strong spin-orbit coupling, with equal Rashba and Dresselhaus strengths, has been created in a trapped Bose-Einstein condensate. Moreover, many exotic superfluid phenomena induced by this strong spin-orbit coupling have been predicted. In this report, we show that this novel spin-orbit coupling has important applications in quantum metrology, such as spin squeezing. We first demonstrate that an effective spin-spin interaction, which is the heart for producing spin squeezing, can be generated by controlling the orbital degree of freedom (i.e., the momentum) of the ultracold atoms. Compared with previous schemes, this realized spin-spin interaction has advantages of no dissipation, high tunability, and strong coupling. More importantly, a giant squeezing factor (lower than -30 dB) can be achieved by tuning a pair of Raman lasers in current experimental setup. Finally, we find numerically that the phase factor of the prepared initial state affects dramatically on spin squeezing.
Tunable Spin-orbit Coupling and Quantum Phase Transition in a Trapped Bose-Einstein Condensate
Zhang, Yongping; Chen, Gang; Zhang, Chuanwei
2013-01-01
Spin-orbit coupling (SOC), the intrinsic interaction between a particle spin and its motion, is responsible for various important phenomena, ranging from atomic fine structure to topological condensed matter physics. The recent experimental breakthrough on the realization of SOC for ultra-cold atoms provides a completely new platform for exploring spin-orbit coupled superfluid physics. However, the SOC strength in the experiment is not tunable. In this report, we propose a scheme for tuning the SOC strength through a fast and coherent modulation of the laser intensities. We show that the many-body interaction between atoms, together with the tunable SOC, can drive a quantum phase transition (QPT) from spin-balanced to spin-polarized ground states in a harmonic trapped Bose-Einstein condensate (BEC), which resembles the long-sought Dicke QPT. We characterize the QPT using the periods of collective oscillations of the BEC, which show pronounced peaks and damping around the quantum critical point. PMID:23727689
Spin-orbit-coupled Bose-Einstein condensates in a circular box
NASA Astrophysics Data System (ADS)
Chen, Yu-Zhu; Xie, Mi
2015-05-01
In this paper we discuss the properties of the ground state of a Rashba spin-orbit (SO) coupled Bose-Einstein condensate (BEC) in a circular box with hard walls, especially the influence of the SO coupling. We first give the analytical solutions for non-interacting particles with Rashba coupling in a circular box. The solution shows that the eigenstate has a Skyrmion-type spin texture, but the Skyrmion charge is usually not an integer, which is different from the case of a harmonic trap. Then, we consider the ground state of a SO-coupled BEC with weak interparticle interaction by numerically solving the Gross-Pitaevskii (GP) equation. We show that a quantum phase transition will appear as the SO coupling strength increases and give the phase diagram. Various aspects of the BEC ground state are discussed, especially their changes before and after the phase transition, such as the energy, the particle distribution, and the spin distribution. When the SO coupling is very strong or the box is very large, the trapped system should be similar to that in free space. We also discuss the relation between the ground states in the box and in free space.
Spin Hall effect in a spinor dipolar Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Oshima, T.; Kawaguchi, Y.
2016-05-01
We theoretically show that the spin Hall effect arises in a Bose-Einstein condensate (BEC) of neutral atoms interacting via the magnetic dipole-dipole interactions (MDDIs). Since the MDDI couples the total spin angular momentum and the relative orbital angular momentum of two colliding atoms, it works as a spin-orbit coupling. Thus, when we prepare a BEC in a magnetic sublevel m =0 , thermally and quantum-mechanically excited atoms in the m =1 and -1 states feel the Lorentz-like forces in the opposite directions. This is the origin for the emergence of the spin Hall effect. We define the mass-current and spin-current operators from the equations of continuity and calculate the spin Hall conductivity from the off-diagonal current-current correlation function within the Bogoliubov approximation. We find that the correction of the current operators due to the MDDI significantly contributes to the spin Hall conductivity. A possible experimental situation is also discussed.
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.
Creating full-Bloch Bose-Einstein condensates with Raman q-plates
NASA Astrophysics Data System (ADS)
Schultz, Justin T.; Hansen, Azure; Murphree, Joseph D.; Jayaseelan, Maitreyi; Bigelow, Nicholas P.
2016-06-01
A coherent two-photon optical Raman interaction in a pseudo-spin-1/2 Bose-Einstein condensate (BEC) serves as a q-plate for atoms, converting spin to orbital angular momentum. This Raman q-plate has a singular pattern in its polarization distribution in analogy to the singular birefringent q-plates used in singular optics. The vortex winding direction and magnitude as well as the final spin state of the BEC depend on the initial spin state and the topology of the optical Raman q-plate beams. Drawing on the mathematical and geometric foundations of singular optics, we derive the equivalent Jones matrix for this Raman q-plate and use it to create and characterize atomic spin singularities in the BEC that are analogous to optical C-point singularities in polarization. By tuning the optical Raman parameters, we can generate a coreless vortex spin texture which contains every possible superposition in a two-state system. We identify this spin texture as a full-Bloch BEC since every point on the Bloch sphere is represented at some point in the cross section of the atomic cloud. This spin-orbit interaction and the spin textures it generates may allow for the observation of interesting geometric phases in matter waves and lead to schemes for topological quantum computation with spinor BECs.
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
2016-01-18
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.
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.
Scaling up the precision in a ytterbium Bose-Einstein condensate interferometer
NASA Astrophysics Data System (ADS)
McAlpine, Katherine; Plotkin-Swing, Benjamin; Gochnauer, Daniel; Saxberg, Brendan; Gupta, Subhadeep
2016-05-01
We report on progress toward a high-precision ytterbium (Yb) Bose-Einstein condensate (BEC) interferometer, with the goal of measuring h/m and thus the fine structure constant α. Here h is Planck's constant and m is the mass of a Yb atom. The use of the non-magnetic Yb atom makes our experiment insensitive to magnetic field noise. Our chosen symmetric 3-path interferometer geometry suppresses errors from vibration, rotation, and acceleration. The precision scales with the phase accrued due to the kinetic energy difference between the interferometer arms, resulting in a quadratic sensitivity to the momentum difference. We are installing and testing the laser pulses for large momentum transfer via Bloch oscillations. We will report on Yb BEC production in a new apparatus and progress toward realizing the atom optical elements for high precision measurements. We will also discuss approaches to mitigate two important systematics: (i) atom interaction effects can be suppressed by creating the BEC in a dynamically shaped optical trap to reduce the density; (ii) diffraction phase effects from the various atom-optical elements can be accounted for through an analysis of the light-atom interaction for each pulse.
Bose-Einstein condensation and critical behavior of two-component bosonic gases
NASA Astrophysics Data System (ADS)
Ceccarelli, Giacomo; Nespolo, Jacopo; Pelissetto, Andrea; Vicari, Ettore
2015-10-01
We study Bose-Einstein condensation (BEC) in three-dimensional two-component bosonic gases, characterizing the universal behaviors of the critical modes arising at the BEC transitions. For this purpose, we use field-theoretical (FT) renormalization-group (RG) methods and perform mean-field and numerical calculations. The FT RG analysis is based on the Landau-Ginzburg-Wilson Φ4 theory with two complex scalar fields which has the same symmetry as the bosonic system. In particular, for identical bosons with exchange Z2 symmetry, coupled by effective density-density interactions, the global symmetry is Z2 ,e⊗U (1 ) ⊗U (1 ) . At the BEC transition, it may break into Z2 ,e⊗Z2⊗Z2 when both components condense simultaneously, or to U (1 ) ⊗Z2 when only one component condenses. This implies different universality classes for the corresponding critical behaviors. Numerical simulations of the two-component Bose-Hubbard model in the hard-core limit support the RG prediction: when both components condense simultaneously, the critical behavior is controlled by a decoupled XY fixed point, with unusual slowly decaying scaling corrections arising from the onsite interspecies interaction.
Clark, Kevin B
2010-03-01
Fringe quantum biology theories often adopt the concept of Bose-Einstein condensation when explaining how consciousness, emotion, perception, learning, and reasoning emerge from operations of intact animal nervous systems and other computational media. However, controversial empirical evidence and mathematical formalism concerning decoherence rates of bioprocesses keep these frameworks from satisfactorily accounting for the physical nature of cognitive-like events. This study, inspired by the discovery that preferential attachment rules computed by complex technological networks obey Bose-Einstein statistics, is the first rigorous attempt to examine whether analogues of Bose-Einstein condensation precipitate learned decision making in live biological systems as bioenergetics optimization predicts. By exploiting the ciliate Spirostomum ambiguum's capacity to learn and store behavioral strategies advertising mating availability into heuristics of topologically invariant computational networks, three distinct phases of strategy use were found to map onto statistical distributions described by Bose-Einstein, Fermi-Dirac, and classical Maxwell-Boltzmann behavior. Ciliates that sensitized or habituated signaling patterns to emit brief periods of either deceptive 'harder-to-get' or altruistic 'easier-to-get' serial escape reactions began testing condensed on initially perceived fittest 'courting' solutions. When these ciliates switched from their first strategy choices, Bose-Einstein condensation of strategy use abruptly dissipated into a Maxwell-Boltzmann computational phase no longer dominated by a single fittest strategy. Recursive trial-and-error strategy searches annealed strategy use back into a condensed phase consistent with performance optimization. 'Social' decisions performed by ciliates showing no nonassociative learning were largely governed by Fermi-Dirac statistics, resulting in degenerate distributions of strategy choices. These findings corroborate
Clark, Kevin B
2010-03-01
Fringe quantum biology theories often adopt the concept of Bose-Einstein condensation when explaining how consciousness, emotion, perception, learning, and reasoning emerge from operations of intact animal nervous systems and other computational media. However, controversial empirical evidence and mathematical formalism concerning decoherence rates of bioprocesses keep these frameworks from satisfactorily accounting for the physical nature of cognitive-like events. This study, inspired by the discovery that preferential attachment rules computed by complex technological networks obey Bose-Einstein statistics, is the first rigorous attempt to examine whether analogues of Bose-Einstein condensation precipitate learned decision making in live biological systems as bioenergetics optimization predicts. By exploiting the ciliate Spirostomum ambiguum's capacity to learn and store behavioral strategies advertising mating availability into heuristics of topologically invariant computational networks, three distinct phases of strategy use were found to map onto statistical distributions described by Bose-Einstein, Fermi-Dirac, and classical Maxwell-Boltzmann behavior. Ciliates that sensitized or habituated signaling patterns to emit brief periods of either deceptive 'harder-to-get' or altruistic 'easier-to-get' serial escape reactions began testing condensed on initially perceived fittest 'courting' solutions. When these ciliates switched from their first strategy choices, Bose-Einstein condensation of strategy use abruptly dissipated into a Maxwell-Boltzmann computational phase no longer dominated by a single fittest strategy. Recursive trial-and-error strategy searches annealed strategy use back into a condensed phase consistent with performance optimization. 'Social' decisions performed by ciliates showing no nonassociative learning were largely governed by Fermi-Dirac statistics, resulting in degenerate distributions of strategy choices. These findings corroborate
Beliaev theory of spinor Bose-Einstein condensates
Phuc, Nguyen Thanh; Kawaguchi, Yuki; Ueda, Masahito
2013-01-15
By generalizing the Green's function approach developed by Beliaev [S.T. Beliaev, Sov. Phys. JETP 7 (1958) 299; S.T. Beliaev, Sov. Phys. JETP 7 (1958) 289], we study effects of quantum fluctuations on the energy spectra of spin-1 spinor Bose-Einstein condensates, in particular, of a {sup 87}Rb condensate in the presence of an external magnetic field. We find that due to quantum fluctuations, the effective mass of magnons, which characterizes the quadratic dispersion relation of spin-wave excitations, increases compared with its mean-field value. The enhancement factor turns out to be the same for two distinct quantum phases: the ferromagnetic and polar phases, and it is a function of only the gas parameter. The lifetime of magnons in a spin-1 {sup 87}Rb spinor condensate is shown to be much longer than that of phonons due to the difference in their dispersion relations. We propose a scheme to measure the effective mass of magnons in a spinor Bose gas by utilizing the effect of magnons' nonlinear dispersion relation on the time evolution of the distribution of transverse magnetization. This type of measurement can be applied, for example, to precision magnetometry. - Highlights: Black-Right-Pointing-Pointer Second-order energy spectra for a spin-1 {sup 87}Rb spinor BEC under a quadratic Zeeman effect are found. Black-Right-Pointing-Pointer Effective mass of magnons increases due to quantum fluctuations. Black-Right-Pointing-Pointer Enhancement factor is the same for two quantum phases and also independent of external parameters. Black-Right-Pointing-Pointer Lifetime of magnons in a spin-1 {sup 87}Rb spinor BEC is much longer than that of phonons. Black-Right-Pointing-Pointer Experimental scheme to measure the effective mass of magnons is proposed.
Bose-Einstein condensate in a rapidly rotating nonsymmetric trap
Fetter, Alexander L.
2010-03-15
A rapidly rotating Bose-Einstein condensate in a symmetric two-dimensional harmonic trap can be described with the lowest Landau-level set of single-particle states. The condensate wave function {psi}(x,y) is a Gaussian {proportional_to}exp(-r{sup 2}/2), multiplied by an analytic function f(z) of the complex variable z=x+iy. The criterion for a quantum phase transition to a non-superfluid correlated many-body state is usually expressed in terms of the ratio of the number of particles to the number of vortices. Here a similar description applies to a rapidly rotating nonsymmetric two-dimensional trap with arbitrary quadratic anisotropy ({omega}{sub x}{sup 2}<{omega}{sub y}{sup 2}). The corresponding condensate wave function {psi}(x,y) is a complex anisotropic Gaussian with a phase proportional to xy, multiplied by an analytic function f(z), where z=x+i{beta}{sub -}y is a stretched complex variable and 0{<=}{beta}{sub -{<=}}1 is a real parameter that depends on the trap anisotropy and the rotation frequency. Both in the mean-field Thomas-Fermi approximation and in the mean-field lowest Landau level approximation with many visible vortices, an anisotropic parabolic density profile minimizes the energy. An elongated condensate grows along the soft trap direction yet ultimately shrinks along the tight trap direction. The criterion for the quantum phase transition to a correlated state is generalized (1) in terms of N/L{sub z}, which suggests that a nonsymmetric trap should make it easier to observe this transition, or (2) in terms of a 'fragmented' correlated state, which suggests that a nonsymmetric trap should make it harder to observe this transition. An alternative scenario involves a crossover to a quasi one-dimensional condensate without visible vortices, as suggested by Aftalion et al., Phys. Rev. A 79, 011603(R) (2009).
Properties of spin-orbit-coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Zhang, Yongping; Mossman, Maren Elizabeth; Busch, Thomas; Engels, Peter; Zhang, Chuanwei
2016-06-01
The experimental and theoretical research of spin-orbit-coupled ultracold atomic gases has advanced and expanded rapidly in recent years. Here, we review some of the progress that either was pioneered by our own work, has helped to lay the foundation, or has developed new and relevant techniques. After examining the experimental accessibility of all relevant spin-orbit coupling parameters, we discuss the fundamental properties and general applications of spin-orbit-coupled Bose-Einstein condensates (BECs) over a wide range of physical situations. For the harmonically trapped case, we show that the ground state phase transition is a Dicke-type process and that spin-orbit-coupled BECs provide a unique platform to simulate and study the Dicke model and Dicke phase transitions. For a homogeneous BEC, we discuss the collective excitations, which have been observed experimentally using Bragg spectroscopy. They feature a roton-like minimum, the softening of which provides a potential mechanism to understand the ground state phase transition. On the other hand, if the collective dynamics are excited by a sudden quenching of the spin-orbit coupling parameters, we show that the resulting collective dynamics can be related to the famous Zitterbewegung in the relativistic realm. Finally, we discuss the case of a BEC loaded into a periodic optical potential. Here, the spin-orbit coupling generates isolated flat bands within the lowest Bloch bands whereas the nonlinearity of the system leads to dynamical instabilities of these Bloch waves. The experimental verification of this instability illustrates the lack of Galilean invariance in the system.
Control of a Bose-Einstein condensate by dissipation: Nonlinear Zeno effect
Shchesnovich, V. S.; Konotop, V. V.
2010-05-15
We show that controlled dissipation can be used as a tool for exploring fundamental phenomena and managing mesoscopic systems of cold atoms and Bose-Einstein condensates. Even the simplest boson-Josephson junction, that is, a Bose-Einstein condensate in a double-well trap, subjected to removal of atoms from one of the two potential minima allows one to observe such phenomena as the suppression of losses and the nonlinear Zeno effect. In such a system the controlled dissipation can be used to create desired macroscopic states and implement controlled switching among different quantum regimes.
Dynamic manipulation of Bose-Einstein condensates with a spatial light modulator
Boyer, V.; Godun, R. M.; Smirne, G.; Cassettari, D.; Chandrashekar, C. M.; Deb, A. B.; Foot, C. J.; Laczik, Z. J.
2006-03-15
We manipulate a Bose-Einstein condensate using the optical trap created by the diffraction of a laser beam on a fast ferroelectric liquid crystal spatial light modulator. The modulator acts as a phase grating which can generate arbitrary diffraction patterns and be rapidly reconfigured at rates up to 1 kHz to create smooth, time-varying optical potentials. The flexibility of the device is demonstrated with our experimental results for splitting a Bose-Einstein condensate and independently transporting the separate parts of the atomic cloud.
Bose-Einstein condensates in strong electric fields: Effective gauge potentials and rotating states
Kailasvuori, J.M.; Hansson, T.H.; Kavoulakis, G.M.
2002-11-01
Magnetically trapped atoms in Bose-Einstein condensates are spin polarized. Since the magnetic field is inhomogeneous, the atoms acquire Berry phases of the Aharonov-Bohm type during adiabatic motion. In the presence of an electric field, there is an additional Aharonov-Casher effect. Taking into account the limitations on the strength of the electric fields due to the polarizability of the atoms, we investigate the extent to which these effects can be used to induce rotation in a Bose-Einstein condensate.
NASA Astrophysics Data System (ADS)
Dujardin, Julien; Engl, Thomas; Schlagheck, Peter
2016-01-01
We study the transport of an interacting Bose-Einstein condensate through a 1D correlated disorder potential. We use for this purpose the truncated Wigner method, which is, as we show, corresponding to the diagonal approximation of a semiclassical van Vleck-Gutzwiller representation of this many-body transport process. We also argue that semiclassical corrections beyond this diagonal approximation are vanishing under disorder average, thus confirming the validity of the truncated Wigner method in this context. Numerical calculations show that, while for weak atom-atom interaction strengths Anderson localization is preserved with a slight modification of the localization length, for larger interaction strengths a crossover to a delocalized regime exists due to inelastic scattering. In this case, the transport is fully incoherent.
Galactic cold dark matter as a Bose-Einstein condensate of WISPs
NASA Astrophysics Data System (ADS)
Pires, M. O. C.; de Souza, J. C. C.
2012-11-01
We propose here the dark matter content of galaxies as a cold bosonic fluid composed of Weakly Interacting Slim Particles (WISPs), represented by spin-0 axion-like particles and spin-1 hidden bosons, thermalized in the Bose-Einstein condensation state and bounded by their self-gravitational potential. We analyze two zero-momentum configurations: the polar phases in which spin alignment of two neighbouring particles is anti-parallel and the ferromagnetic phases in which every particle spin is aligned in the same direction. Using the mean field approximation we derive the Gross-Pitaevskii equations for both cases, and, supposing the dark matter to be a polytropic fluid, we describe the particles density profile as Thomas-Fermi distributions characterized by the halo radii and in terms of the scattering lengths and mass of each particle. By comparing this model with data obtained from 42 spiral galaxies and 19 Low Surface Brightness (LSB) galaxies, we constrain the dark matter particle mass to the range 10-6-10-4 eV and we find the lower bound for the scattering length to be of the order 10-14 fm.
NASA Astrophysics Data System (ADS)
Lovegrove, Justin; Borgh, Magnus O.; Ruostekoski, Janne
2016-03-01
We demonstrate how conservation of longitudinal magnetization can have pronounced effects on both stability and structure of vortices in the atomic spin-1 Bose-Einstein condensate by providing a systematic characterization of nonsingular and singular vortex states. Constructing spinor wave functions for vortex states that continuously connect ferromagnetic and polar phases, we systematically derive analytic models for nonrotating cores of different singular vortices and for composite defect states with distinct small- and large-distance topology. We explain how the conservation law provides a stabilizing mechanism when the coreless vortex imprinted on the condensate relaxes in the polar regime of interatomic interactions. The resulting structure forms a composite defect: The inner ferromagnetic coreless vortex deforms toward an outer singly quantized polar vortex. We also numerically show how other even more complex hierarchies of vortex-core topologies may be stabilized. Moreover, we analyze the structure of the coreless vortex also in a ferromagnetic condensate and show how reducing magnetization leads to a displacement of the vortex from the trap center and eventually to the deformation and splitting of its core where a singular vortex becomes a lower-energy state. For the case of singular vortices, we find that the stability and the core structure are notably less influenced by the conservation of magnetization.
Theory of combined photoassociation and Feshbach resonances in a Bose-Einstein condensate
Mackie, Matt; DeBrosse, Catherine
2010-04-15
We model combined photoassociation and Feshbach resonances in a Bose-Einstein condensate, where the shared dissociation continuum allows for quantum interference in losses from the condensate, as well as a dispersive-like shift of resonance. A seemingly oversimplified model is revisited, explaining it as based on the limit of weakly bound molecules, reinforcing it with a comparison to numerical experiments that explicitly include dissociation to noncondensate modes, comparing it against the unitarity limit on condensate losses, and lastly, checking its universal implications. In particular, for a resonant laser and an off-resonant magnetic field, these numerical experiments reveal a rate limit on condensate losses that is larger for smaller condensate densities, approaches the rate limit for magnetoassociation alone near the Feshbach resonance, and agrees best with the analytical model for low density. Comparing the analytical rate limit against the unitary limit, which is set by the size of the condensate, agreement is found only for a limited range of near-resonant magnetic fields. Finally, for a resonant magnetic field and an off-resonant laser, the analytical shift of the Feshbach resonance is found to depend on the size of the Feshbach molecule, signifying nonuniversal physics in a strongly interacting system.
Galactic cold dark matter as a Bose-Einstein condensate of WISPs
Pires, M.O.C.; Souza, J.C.C. de E-mail: jose.souza@ufabc.edu.br
2012-11-01
We propose here the dark matter content of galaxies as a cold bosonic fluid composed of Weakly Interacting Slim Particles (WISPs), represented by spin-0 axion-like particles and spin-1 hidden bosons, thermalized in the Bose-Einstein condensation state and bounded by their self-gravitational potential. We analyze two zero-momentum configurations: the polar phases in which spin alignment of two neighbouring particles is anti-parallel and the ferromagnetic phases in which every particle spin is aligned in the same direction. Using the mean field approximation we derive the Gross-Pitaevskii equations for both cases, and, supposing the dark matter to be a polytropic fluid, we describe the particles density profile as Thomas-Fermi distributions characterized by the halo radii and in terms of the scattering lengths and mass of each particle. By comparing this model with data obtained from 42 spiral galaxies and 19 Low Surface Brightness (LSB) galaxies, we constrain the dark matter particle mass to the range 10{sup −6}–10{sup −4} eV and we find the lower bound for the scattering length to be of the order 10{sup −14} fm.
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.
Faraday and resonant waves in binary collisionally-inhomogeneous Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Sudharsan, J. B.; Radha, R.; Carina Raportaru, Mihaela; Nicolin, Alexandru I.; Balaž, Antun
2016-08-01
We study Faraday and resonant waves in two-component quasi-one-dimensional (cigar-shaped) collisionally inhomogeneous Bose-Einstein condensates subject to periodic modulation of the radial confinement. We show by means of extensive numerical simulations that, as the system exhibits stronger spatially-localised binary collisions (whose scattering length is taken for convenience to be of Gaussian form), the system becomes effectively a linear one. In other words, as the scattering length approaches a delta-function, we observe that the two nonlinear configurations typical for binary cigar-shaped condensates, namely the segregated and the symbiotic one, turn into two overlapping Gaussian wave functions typical for linear systems, and that the instability onset times of the Faraday and resonant waves become longer. Moreover, our numerical simulations show that the spatial period of the excited waves (either resonant or Faraday ones) decreases as the inhomogeneity becomes stronger. Our results also demonstrate that the topology of the ground state impacts the dynamics of the ensuing density waves, and that the instability onset times of Faraday and resonant waves, for a given level of inhomogeneity in the two-body interactions, depend on whether the initial configuration is segregated or symbiotic.
SO(2)-induced breathing patterns in multicomponent Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Charalampidis, E. G.; Wang, Wenlong; Kevrekidis, P. G.; Frantzeskakis, D. J.; Cuevas-Maraver, J.
2016-06-01
In this work, we employ the SO (2 ) rotations of a two-component, one-, two-, and three-dimensional nonlinear Schrödinger system at and near the Manakov limit to construct vector solitons and vortex structures. In this way, stable stationary dark-bright solitons and their higher-dimensional siblings are transformed into robust oscillatory dark-dark solitons (and generalizations thereof) with and without a harmonic confinement. By analogy to the one-dimensional case, vector higher-dimensional structures take the form of vortex-vortex states in two dimensions and, e.g., vortex-ring-vortex-ring ones in three dimensions. We consider the effects of unequal (self- and cross-) interaction strengths, where the SO (2 ) symmetry is only approximately satisfied, showing the dark-dark soliton oscillation is generally robust. Similar features are found in higher dimensions too, although our examples suggest that phenomena such as phase separation may contribute to the associated dynamics. These results, in connection with the experimental realization of one-dimensional variants of such states in optics and Bose-Einstein condensates, suggest the potential observability of the higher-dimensional bound states proposed herein.
Jiang, Jian-Hua; John, Sajeev
2014-01-01
Semiconductor-microcavity polaritons are composite quasiparticles of excitons and photons, emerging in the strong coupling regime. As quantum superpositions of matter and light, polaritons have much stronger interparticle interactions compared with photons, enabling rapid equilibration and Bose-Einstein condensation (BEC). Current realizations based on 1D photonic structures, such as Fabry-Pérot microcavities, have limited light-trapping ability resulting in picosecond polariton lifetime. We demonstrate, theoretically, above-room-temperature (up to 590 K) BEC of long-lived polaritons in MoSe2 monolayers sandwiched by simple TiO2 based 3D photonic band gap (PBG) materials. The 3D PBG induces very strong coupling of 40 meV (Rabi splitting of 62 meV) for as few as three dichalcogenide monolayers. Strong light-trapping in the 3D PBG enables the long-lived polariton superfluid to be robust against fabrication-induced disorder and exciton line-broadening. PMID:25503586
A novel experiment for coupling a Bose-Einstein condensate with two crossed cavity modes
NASA Astrophysics Data System (ADS)
Donner, Tobias; Leonard, Julian; Lee, Moojnoo; Morales, Andrea; Karg, Thomas; Esslinger, Tilman
2014-05-01
Over the last decade, combining cavity quantum electrodynamics and quantum gases allowed to explore the coupling of quantized light fields to coherent matter waves, leading e.g. to new optomechanical phenomena and the realization of quantum phase transitions. Triggered by the interest to study setups with more complex cavity geometries, we built a novel, highly flexible experimental system for coupling a Bose-Einstein condensate (BEC) with optical cavities, which allows to switch the cavity setups by means of an interchangeable science platform. The BEC is generated from a cloud of laser-cooled 87-Rb atoms which is first loaded into a hybrid trap, formed by a combined magnetic and optical potential, and then optically transported into the cavity setup, where it is cooled down to quantum degeneracy. At first we aim to explore the coupling of a BEC with two crossed cavity modes. We report on our progress on the implementation of a science setup involving two cavities intersecting under an angle of 60°. his setup will allow us to study the coherent interaction of a BEC and the two cavity modes both in internal lambda-level transitions and in spatial self-organization processes in dynamical hexagonal lattices.
NASA Astrophysics Data System (ADS)
Jiang, Zhang; Caves, Carlton M.
2016-03-01
We encode the many-body wave function of a Bose-Einstein condensate (BEC) in the N -particle sector of an extended catalytic state. This catalytic state is a coherent state for the condensate mode and an arbitrary state for the modes orthogonal to the condensate mode. Going to a time-dependent interaction picture where the state of the condensate mode is displaced to the vacuum, we can organize the effective Hamiltonian by powers of N-1 /2. Requiring the terms of order N1 /2 to vanish gives the Gross-Pitaevskii equation. Going to the next order, N0, we derive equations for the number-conserving Bogoliubov approximation, first given by Castin and Dum [Phys. Rev. A 57, 3008 (1998), 10.1103/PhysRevA.57.3008]. In contrast to other approaches, ours is well suited to calculating the state evolution in the Schrödinger picture; moreover, it is straightforward to generalize our method to multicomponent BECs and to higher-order corrections.
Finite-temperature effects in stirred ring Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Murray, N.; Lanier, C.; Edwards, M.; Wang, Y.-H.; Clark, C. W.
2014-05-01
A ring Bose-Einstein condensate (BEC) with zero circulation (m = 0) stirred by a barrier will eventually jump to an m = 1 state when stirred faster than a certain critical speed, Ωc+. A ring BEC with m = 1 will drop to m = 0 when stirred at a critical speed, Ωc-, which is lower than Ωc+. The loop areas, Ωc+ -Ωc- , of this hysteretic response of the BEC to stirring predicted by zero-temperature Gross-Pitaevskii equation (GPE) disagreed significantly with the results of a recent experiment. In the work reported here, we simulated this experiment with the phenomenologically damped GPE, [S. Choi, S. A. Morgan, and K. Burnett, Phys. Rev. A 57, 4057 (1999)], and with the Zaremba-Nikuni-Griffin (ZNG) theory. The ZNG theory can account for finite-T, non-equilibrium dynamics. We compare the results of these simulations with the experimental data. The simulations show that a vortex/antivortex pair forms in the barrier region during the stirring and that this drives the hysteresis. We also show how the presence of an interacting, thermal cloud affects the dynamics of these pairs. We also simulate a ring condensate stirred by two barriers and find that the GPE matches the data much more closely. Supported in part by NSF grant #1068761 and ARO Atomtronics MURI.
Finite-temperature effects in rotational hysteresis of ring Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Murray, N.; Lanier, C.; Edwards, M.; Wang, Y.-H.; Clark, C. W.; Eckel, S.; Jendrzejewski, F.; Campbell, G. K.
2014-03-01
A ring Bose-Einstein condensate (BEC) with zero circulation (m = 0) stirred by a barrier will eventually jump to an m = 1 state when stirred faster than a certain critical speed, Ωc+. A ring BEC with m = 1 will drop to m = 0 when stirred at a critical speed, Ωc-, which is lower than Ωc+. The loop areas, Ωc+ -Ωc- , of this hysteretic response of the BEC to stirring predicted by zero-temperature Gross-Pitaevskii equation (GPE) disagreed significantly with the results of a recent experiment. In the work reported here, we simulated this experiment with the phenomenologically damped GPE, [S. Choi, S. A. Morgan, and K. Burnett, Phys. Rev. A 57, 4057 (1999)], and with the Zaremba-Nikuni-Griffin (ZNG) theory. The ZNG theory can account for finite-T, non-equilibrium dynamics. We compare the results of these simulations with the experimental data. The simulations show that a vortex/antivortex pair forms in the barrier region during the stirring and that this drives the hysteresis. We also show how the presence of an interacting, thermal cloud affects the dynamics of these pairs. Supported in part by NSF grant #1068761 and ARO Atomtronics MURI
Probing a scattering resonance with Rydberg molecules inside a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Perez-Rios, J.; Schlagmüller, M.; Liebisch, T. C.; Nguyen, H.; Lochead, G.; Engel, F.; Böottcher, F.; Westphal, K. M.; Kleinbach, K. S.; Löw, R.; Hofferberth, S.; Pfau, T.; Greene, C. H.
2016-05-01
The spectroscopy of a single Rydberg atom within a Bose-Einstein condensate is studied, and as a result a line shape dependence on the principal Rydberg quantum number n is observed, apart from the expected density shift due to the large number of neutrals inside the Rydberg orbit. The observed line broadening depends on the Rydberg electron-neutral interaction, in particular, it manifests the influence of the e-Rb(5S) p-wave scattering shape resonance, which dramatically affects the potential energy landscape for the neutrals embedded within the Rydberg orbit. The observed spectroscopic line shapes are reproduced with an overall good agreement by means of a microscopic model, in which the atoms overlapped with the Rydberg orbit are treated as zero-velocity point-like particles, with binding energies associated with the ion-neutral distance. We acknowledge support from Deutsche Forschungsge5 meinschaft (DFG) within the SFB/TRR21 and the project PF 381/13-1. This work has been supported by NSF under Grand Number PHY-130690.
Vortices in dipolar Bose-Einstein condensates in synthetic magnetic field
NASA Astrophysics Data System (ADS)
Qiang, Zhao; Qiang, Gu
2016-01-01
We study the formation of vortices in a dipolar Bose-Einstein condensate in a synthetic magnetic field by numerically solving the Gross-Pitaevskii equation. The formation process depends on the dipole strength, the rotating frequency, the potential geometry, and the orientation of the dipoles. We make an extensive comparison with vortices created by a rotating trap, especially focusing on the issues of the critical rotating frequency and the vortex number as a function of the rotating frequency. We observe that a higher rotating frequency is needed to generate a large number of vortices and the anisotropic interaction manifests itself as a perceptible difference in the vortex formation. Furthermore, a large dipole strength or aspect ratio also can increase the number of vortices effectively. In particular, we discuss the validity of the Feynman rule. Project supported by the National Natural Science Foundation of China (Grant No. 11274039), the National Basic Research Program of China (Grant No. 2013CB922002), and the Fundamental Research Funds for the Central Universities of China.
Persistent currents in coherently coupled Bose-Einstein condensates in a ring trap
NASA Astrophysics Data System (ADS)
Abad, Marta
2016-03-01
We study the stability of persistent currents in a coherently coupled quasi-two-dimensional Bose-Einstein condensate confined in a ring trap at T =0 . By numerically solving Gross-Pitaevskii equations and by analyzing the excitation spectrum obtained from diagonalization of the Bogoliubov-de Gennes matrix, we describe the mechanisms responsible for the decay of the persistent currents depending on the values of the interaction coupling constants and the Rabi frequency. When the unpolarized system decays due to an energetic instability in the density channel, the spectrum may develop a rotonlike minimum, which gives rise to the finite wavelength excitation necessary for vortex nucleation at the inner surface. When decay in the unpolarized system is driven by spin-density excitations, the finite wavelength naturally arises from the existence of a gap in the excitation spectrum. In the polarized phase of the coherently coupled condensate, there is a hybridization of the excitation modes that leads to complex decay dynamics. In particular, close to the phase transition, a state of broken rotational symmetry is found to be stationary and stable.
Fractality and macroscopic entanglement in two-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Byrnes, Tim
2013-08-01
Spin coherent states are the matter equivalent of optical coherent states, where a large number of two component particles form a macroscopic state displaying quantum coherence. Here we give a detailed study of entanglement generated between two spin-1/2 Bose-Einstein condensates (BECs) due to an S1zS2z interaction. The states that are generated show a remarkably rich structure showing fractal characteristics. In the limit of large particle number N, the entanglement shows a strong dependence upon whether the entangling gate times are a rational or irrational multiple of π/4, with a fractal dimension of d≈1.7. We discuss the robustness of various states under decoherence and show that despite the large number of particles in a typical BEC, entanglement on a macroscopic scale should be observable as long as the gate times are less than ℏ/JN, where J is the effective BEC-BEC coupling energy. Such states are anticipated to be useful for various quantum information applications such as quantum teleportation and quantum algorithms.
Quasi one-dimensional Bose-Einstein condensate in a gravito-optical surface trap
NASA Astrophysics Data System (ADS)
Akram, Javed; Girodias, Benjamin; Pelster, Axel
2016-04-01
We study both static and dynamic properties of a weakly interacting Bose-Einstein condensate (BEC) in a quasi one-dimensional gravito-optical surface trap, where the downward pull of gravity is compensated by the exponentially decaying potential of an evanescent wave. First, we work out approximate solutions of the Gross-Pitaevskii equation for both a small number of atoms using a Gaussian ansatz and a larger number of atoms using the Thomas-Fermi limit. Then we confirm the accuracy of these analytical solutions by comparing them to numerical results. From there, we numerically analyze how the BEC cloud expands non-ballistically, when the confining evanescent laser beam is shut off, showing agreement between our theoretical and previous experimental results. Furthermore, we analyze how the BEC cloud expands non-ballistically due to gravity after switching off the evanescent laser field in the presence of a hard-wall mirror which we model by using a blue-detuned far-off-resonant sheet of light. There we find that the BEC shows significant self-interference patterns for a large number of atoms, whereas for a small number of atoms, a revival of the BEC wave packet with few matter-wave interference patterns is observed.
Bargueño, Pedro; Pérez de Tudela, Ricardo; Miret-Artés, Salvador; Gonzalo, Isabel
2011-01-21
Interactions which do not conserve parity might influence chiral compounds giving rise to a parity violating energy difference (PVED) that might have affected the evolution towards homochirality. However, this tiny effect predicted by electroweak-quantum chemistry calculations is easily masked by thermal effects, making it desirable to reach cold regimes in the laboratory. As an alternative route to the detection of the PVED, we study a simplified model of Bose-Einstein condensation of a sample of non-interacting chiral molecules, showing that it leads to a nonzero optical activity of the condensate and also to a subcritical temperature in the heat capacity, due to the internal structure of the molecule characterized by tunneling and parity violation. This predicted singular behavior found for the specific heat, below the condensation temperature, might shed some light on the existence of the thus far elusive PVED between enantiomers.
NASA Astrophysics Data System (ADS)
You, Jhih-Shih; Liu, I.-Kang; Wang, Daw-Wei; Gou, Shih-Chuan; Wu, Congjun
We investigate the unconventional Bose-Einstein condensations of two-species mixture with p-wave symmetry in the second band of a bipartite optical lattice. Different from the single-species case, the two-species boson mixture exhibits two non-equivalent complex BECs in the intraspecies-interaction-dominating regime, with one breaking time-reversal symmetry while the other not. When the interspecies interaction is tuned across the SU(2) invariant point, the system undergoes a quantum phase transition toward a real-valued checkerboard state characterized by a staggered spin density structure. An experimental scheme for phase measurement is presented. Finally, we will show strong coupling analysis on anti-Hund'srule, Mott-insulating states and the superfluid.
Ultraslow, stopped, and compressed light in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Dutton, Zachary John
We present theoretical analysis and experimental results of methods to achieve and use ultraslow light (USL), stopped light, and compressed light in sodium Bose-Einstein condensates (BECs). We present applications of these methods to study and harness both the coherent and superfluid properties of BECs. A description of the propagation of probe and coupling laser fields in three-level Λ configuration atoms is presented in a semiclassical description. This formalism is used to derive how electromagnetically induced transparency (EIT) and USL arise. We present novel theoretical results on the effect a fourth level, and effects of nonlinearities associated with a strong probe. Experimental demonstration of ultraslow light is presented. A description which includes atomic motion in Bose-condensed samples of alkali atoms is developed in a mean field description and coupled Gross-Pitaevskii equations are derived. A numerical code which solves these equations is presented. An analytic and numerical analysis reveal the limits on ultraslow light and compressed light imposed by the external atomic dynamics. We then show that using USL and switching the coupling field off allows storage of the coherent probe pulse information (amplitude and phase) in the atomic fields. Switching the coupling beam back on writes the coherent information back onto the probe field. Experimental demonstration is presented. We present experimental data and theoretical analysis showing how stopping light in a BEC creates an atom laser with the highest reported phase space density flux to date. Alternatively, reviving the probe pulse after significant BEC dynamics can be used to process the information before it is written back onto the probe. Possible applications to quantum processing are discussed. We then present results on a light "roadblock", whereby blocking part of the coupling field spatially compresses probe pulses to sizes on the order of the condensate healing length. The compressed
Sykes, Andrew G; Davis, Matthew J; Roberts, David C
2009-08-21
The existence of frictionless flow below a critical velocity for obstacles moving in a superfluid is well established in the context of the mean-field Gross-Pitaevskii theory. We calculate the next order correction due to quantum and thermal fluctuations and find a nonzero force acting on a delta-function impurity moving through a quasi-one-dimensional Bose-Einstein condensate at all subcritical velocities and at all temperatures. The force occurs due to an imbalance in the Doppler shifts of reflected quantum fluctuations from either side of the impurity. Our calculation is based on a consistent extension of Bogoliubov theory to second order in the interaction strength, and finds new analytical solutions to the Bogoliubov-de Gennes equations for a gray soliton. Our results raise questions regarding the quantum dynamics in the formation of persistent currents in superfluids.
Kudo, Kazue; Kawaguchi, Yuki
2011-10-15
The hydrodynamic equation of a spinor Bose-Einstein condensate (BEC) gives a simple description of spin dynamics in the condensate. We introduce the hydrodynamic equation of a ferromagnetic BEC with dissipation originating from the energy dissipation of the condensate. The dissipative hydrodynamic equation has the same form as an extended Landau-Lifshitz-Gilbert (LLG) equation, which describes the magnetization dynamics of conducting ferromagnets in which localized magnetization interacts with spin-polarized currents. Employing the dissipative hydrodynamic equation, we demonstrate the magnetic domain pattern dynamics of a ferromagnetic BEC in the presence and absence of a current of particles, and discuss the effects of the current on domain pattern formation. We also discuss the characteristic lengths of domain patterns that have domain walls with and without finite magnetization.
NASA Astrophysics Data System (ADS)
Hoashi, M.; Nakamura, Y.; Yamanaka, Y.
2016-04-01
The dynamical instability of weakly interacting two-component Bose-Einstein condensates with coaxial quantized vortices is analytically investigated in a two-dimensional isotopic harmonic potential. We examine whether complex eigenvalues appear on the Bogoliubov-de Gennes equation, implying dynamical instability. Rather than solving the Bogoliubov-de Gennes equation numerically, we rely on a perturbative expansion with respect to the coupling constant which enables a simple, analytic approach. For each pair of winding numbers and for each magnetic quantum number, the ranges of intercomponent coupling constant where the system is dynamically unstable are exhaustively obtained. Corotating and counter-rotating systems show distinctive behaviors. The latter is much more complicated than the former with respect to dynamical instability, particularly because radial excitations contribute to complex eigenvalues in counter-rotating systems.
NASA Astrophysics Data System (ADS)
Liao, Renyuan; Fialko, Oleksandr; Brand, Joachim; Zülicke, Ulrich
2015-10-01
We theoretically study homogeneously trapped atomic Bose-Einstein condensates where all three-momentum components couple to a pseudo-spin-1/2 degree of freedom. Tuning the anisotropies of spin-orbit coupling and the spin-dependent interactions is shown to provide access to a rich phase diagram with a tetracritical point, first-order phase transitions, and multiple metastable phases of stripe and plane-wave character. The elementary excitation spectrum of the axial plane-wave phase features an anisotropic roton feature and can be used to probe the phase diagram. In addition to providing a versatile laboratory for studying fundamental concepts in statistical physics, the emergence of metastable phases creates new opportunities for observing false-vacuum decay and bubble nucleation in ultracold-atom experiments.
Photoassociation spectroscopy of 174 Yb Bose-Einstein Condensate using the 1 S0<-->3 P1 transition
NASA Astrophysics Data System (ADS)
Mun, Jongchul; Lee, Jeongwon; Lee, Jae Hoon; Kim, Min-Seok; Shin, Yong-Il
2016-05-01
We studied the photoassociation spectrum of 174 Yb Bose-Einstein condensate (BEC) using an optical Feshbach resonance near the intercombination transition (1 S0 -3 P1, 578 nm). The optical length lopt, which characterize the interaction strength of optical Feshbach resonances, of four least-bound molecular levels (ν' = - 1 ~ - 4) were precisely determined by measuring the two-body loss rate at various optical powers. We also found the parameter η =Γspon /Γmol , which characterizes the enhancement of molecular loss, to be > 1 as in the previous studies. Our BEC apparatus and experimental scheme are also introduced in this presentation. This work was supported by KRISS creative research initiative.
NASA Astrophysics Data System (ADS)
Nematollahi, Delaram; Zhang, Qimin; Altermatt, Joseph; Zhong, Shan; Goodman, Matthew; Bhagat, Anita; Schwettmann, Arne
2016-05-01
We present our apparatus designed to study matter-wave quantum optics in spin space, including our recently finished vacuum system and laser systems. Microwave-dressed spin-exchange collisions in a sodium spinor Bose-Einstein condensate provide a precisely controllable nonlinear interaction that generates squeezing and acts as a source of entanglement. As a consequence of this entanglement between atoms with magnetic quantum numbers m = +1 and m = -1, the noise of population measurements can be reduced below the shot noise. Versatile microwave pulse sequences will be used to implement an interferometer, a phase-sensitive amplifier and other devices. With an added ion detector to detect Rydberg atoms via pulsed-field ionization, we plan to study the effect of Rydberg excitations on the spin evolution of the ultracold gas.
NASA Astrophysics Data System (ADS)
Borgh, Magnus O.; Ruostekoski, Janne
2016-05-01
We demonstrate that multiple interaction-dependent defect core structures as well as dynamics of non-Abelian vortices can be realized in the biaxial nematic (BN) phase of a spin-2 atomic Bose-Einstein condensate (BEC). An experimentally simple protocol may be used to break degeneracy with the uniaxial nematic phase. We show that a discrete spin-space symmetry in the core may be reflected in a breaking of its spatial symmetry. The discrete symmetry of the BN order parameter leads to non-commuting vortex charges. We numerically simulate reconnection of non-Abelian vortices, demonstrating formation of the obligatory rung vortex. In addition to atomic BECs, non-Abelian vortices are theorized in, e.g., liquid crystals and cosmic strings. Our results suggest the BN spin-2 BEC as a prime candidate for their realization. We acknowledge financial support from the EPSRC.
NASA Astrophysics Data System (ADS)
Vilchynskyy, S. I.; Yakimenko, A. I.; Isaieva, K. O.; Chumachenko, A. V.
2013-09-01
We present a brief overview of crucial historical stages in creation of superfluidity theory and of the current state of the microscopic theory of superfluid 4He. We pay special attention to the role of Bose-Einstein condensates (BECs) in understanding of physical mechanisms of superfluidity and identification of quantum mechanical structure of 4He superfluid component below λ-point, in particular—the possibility that at least two types of condensates may appear and coexist simultaneously in superfluid 4He. In this context we discuss the properties of the binary mixtures of BECs and types of excitations, which may appear due to intercomponent interaction in such binary mixtures of condensates. We also discuss current status of investigations of persistent currents in toroidal optical traps and present an outlook of our recent findings on this subject.
Bogoliubov theory of a Bose-Einstein condensate in the particle representation
Dziarmaga, Jacek; Sacha, Krzysztof
2003-03-01
In the number-conserving Bogoliubov theory of the Bose-Einstein condensate, the Bogoliubov transformation between quasiparticles and particles is nonlinear. We invert this nonlinear transformation and give a general expression for eigenstates of the Bogoliubov Hamiltonian in particle representation. The particle representation unveils the structure of a condensate multiparticle wave function. We give several examples to illustrate a general formalism.
Frausto-Solis, Juan; Liñán-García, Ernesto; Sánchez-Hernández, Juan Paulo; González-Barbosa, J Javier; González-Flores, Carlos; Castilla-Valdez, Guadalupe
2016-01-01
A new hybrid Multiphase Simulated Annealing Algorithm using Boltzmann and Bose-Einstein distributions (MPSABBE) is proposed. MPSABBE was designed for solving the Protein Folding Problem (PFP) instances. This new approach has four phases: (i) Multiquenching Phase (MQP), (ii) Boltzmann Annealing Phase (BAP), (iii) Bose-Einstein Annealing Phase (BEAP), and (iv) Dynamical Equilibrium Phase (DEP). BAP and BEAP are simulated annealing searching procedures based on Boltzmann and Bose-Einstein distributions, respectively. DEP is also a simulated annealing search procedure, which is applied at the final temperature of the fourth phase, which can be seen as a second Bose-Einstein phase. MQP is a search process that ranges from extremely high to high temperatures, applying a very fast cooling process, and is not very restrictive to accept new solutions. However, BAP and BEAP range from high to low and from low to very low temperatures, respectively. They are more restrictive for accepting new solutions. DEP uses a particular heuristic to detect the stochastic equilibrium by applying a least squares method during its execution. MPSABBE parameters are tuned with an analytical method, which considers the maximal and minimal deterioration of problem instances. MPSABBE was tested with several instances of PFP, showing that the use of both distributions is better than using only the Boltzmann distribution on the classical SA.
Comment on 'Feshbach resonance and growth of a Bose-Einstein condensate'
Wu, Lei; Jiang, Ren-Jie; Pei, Yu-hua; Zhang, Jie-Fang
2007-03-15
Our analytical solution shows that the number of atoms continuously injected into Bose-Einstein condensate from the reservoir depends on the linear gain/loss coefficient, and cannot be controlled by applying the external magnetic field via Feshbach resonance reported by Yuce and Kilic [Phys. Rev. A 74, 033609 (2006)].
Bogoliubov space of a Bose-Einstein condensate and quantum spacetime fluctuations
Rivas, J. I.; Camacho, A.; Goeklue, E.
2012-08-24
We analyze the role that metric fluctuations could have on the features of a Bose-Einstein condensate. Particularly, the Bogoliubov space associated to it is considered and it will be shown that the pressure and the speed of sound of the ground state define an expression allowing us to determine the average size of these fluctuations.
Zero-Temperature, Mean-Field Theory of Atomic Bose-Einstein Condensates
Edwards, Mark; Dodd, R. J.; Clark, Charles W.; Burnett, K.
1996-01-01
We review the application of zero-temperature, mean-field theory to current experimental atomic Bose-Einstein condensates. We assess the validity of the approximations made by comparing the mean-field results with a variety of experimental data.
Quantum Entanglement and Spin Squeezing of Two Species Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Li, Song-Song
2016-09-01
We investigate quantum entanglement and spin squeezing of two species Bose-Einstein condensates. By the rotating-wave approximation, we obtain the effective Hamiltonian and the wave function of the system. It's shown that more entanglement and squeezing may be achieved by increasing the population difference of particles.
Liñán-García, Ernesto; Sánchez-Hernández, Juan Paulo; González-Barbosa, J. Javier; González-Flores, Carlos
2016-01-01
A new hybrid Multiphase Simulated Annealing Algorithm using Boltzmann and Bose-Einstein distributions (MPSABBE) is proposed. MPSABBE was designed for solving the Protein Folding Problem (PFP) instances. This new approach has four phases: (i) Multiquenching Phase (MQP), (ii) Boltzmann Annealing Phase (BAP), (iii) Bose-Einstein Annealing Phase (BEAP), and (iv) Dynamical Equilibrium Phase (DEP). BAP and BEAP are simulated annealing searching procedures based on Boltzmann and Bose-Einstein distributions, respectively. DEP is also a simulated annealing search procedure, which is applied at the final temperature of the fourth phase, which can be seen as a second Bose-Einstein phase. MQP is a search process that ranges from extremely high to high temperatures, applying a very fast cooling process, and is not very restrictive to accept new solutions. However, BAP and BEAP range from high to low and from low to very low temperatures, respectively. They are more restrictive for accepting new solutions. DEP uses a particular heuristic to detect the stochastic equilibrium by applying a least squares method during its execution. MPSABBE parameters are tuned with an analytical method, which considers the maximal and minimal deterioration of problem instances. MPSABBE was tested with several instances of PFP, showing that the use of both distributions is better than using only the Boltzmann distribution on the classical SA. PMID:27413369
Observation of phase defects in quasi-two-dimensional Bose-Einstein condensates.
Stock, Sabine; Hadzibabic, Zoran; Battelier, Baptiste; Cheneau, Marc; Dalibard, Jean
2005-11-01
We have observed phase defects in quasi-2D Bose-Einstein condensates close to the condensation temperature. Either a single or several equally spaced condensates are produced by selectively evaporating the sites of a 1D optical lattice. When several clouds are released from the lattice and allowed to overlap, dislocation lines in the interference patterns reveal nontrivial phase defects.
Excess noise depletion of a Bose-Einstein condensate in an optical cavity.
Szirmai, G; Nagy, D; Domokos, P
2009-02-27
Quantum fluctuations of a cavity field coupled into the motion of ultracold bosons can be strongly amplified by a mechanism analogous to the Petermann excess noise factor in lasers with unstable cavities. For a Bose-Einstein condensate in a stable optical resonator, the excess noise effect amounts to a significant depletion on long time scales. PMID:19257722
On three-dimensional dynamics of oscillons of Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Rosanov, N. N.
2015-12-01
Three-dimensional motion of the center of the localized structure of atomic Bose-Einstein condensate in a dynamic trap has been analyzed. The transverse and longitudinal motions of the structure center are separated within the approximation of Newtonian-type mechanical equation. The transverse-motion equations are solved for the axisymmetric and quadratic transverse potentials.
Excess Noise Depletion of a Bose-Einstein Condensate in an Optical Cavity
Szirmai, G.; Nagy, D.; Domokos, P.
2009-02-27
Quantum fluctuations of a cavity field coupled into the motion of ultracold bosons can be strongly amplified by a mechanism analogous to the Petermann excess noise factor in lasers with unstable cavities. For a Bose-Einstein condensate in a stable optical resonator, the excess noise effect amounts to a significant depletion on long time scales.
Structure of vortex shedding past potential barriers moving in a Bose-Einstein condensate
Mironov, V. A.; Smirnov, A. I. Smirnov, L. A.
2010-05-15
The problem of excitation of a homogeneous Bose-Einstein condensate by axially symmetric potential barriers moving with respect to the condensate with both supersonic and subsonic velocities is considered in terms of the Gross-Pitaevskii equation. The specific features of the structure of the vortex shedding past the barriers are analyzed for both regimes of motion.
The Evolution of Hyperedge Cardinalities and Bose-Einstein Condensation in Hypernetworks
Guo, Jin-Li; Suo, Qi; Shen, Ai-Zhong; Forrest, Jeffrey
2016-01-01
To depict the complex relationship among nodes and the evolving process of a complex system, a Bose-Einstein hypernetwork is proposed in this paper. Based on two basic evolutionary mechanisms, growth and preference jumping, the distribution of hyperedge cardinalities is studied. The Poisson process theory is used to describe the arrival process of new node batches. And, by using the Poisson process theory and a continuity technique, the hypernetwork is analyzed and the characteristic equation of hyperedge cardinalities is obtained. Additionally, an analytical expression for the stationary average hyperedge cardinality distribution is derived by employing the characteristic equation, from which Bose-Einstein condensation in the hypernetwork is obtained. The theoretical analyses in this paper agree with the conducted numerical simulations. This is the first study on the hyperedge cardinality in hypernetworks, where Bose-Einstein condensation can be regarded as a special case of hypernetworks. Moreover, a condensation degree is also discussed with which Bose-Einstein condensation can be classified. PMID:27669903
Frausto-Solis, Juan; Liñán-García, Ernesto; Sánchez-Hernández, Juan Paulo; González-Barbosa, J Javier; González-Flores, Carlos; Castilla-Valdez, Guadalupe
2016-01-01
A new hybrid Multiphase Simulated Annealing Algorithm using Boltzmann and Bose-Einstein distributions (MPSABBE) is proposed. MPSABBE was designed for solving the Protein Folding Problem (PFP) instances. This new approach has four phases: (i) Multiquenching Phase (MQP), (ii) Boltzmann Annealing Phase (BAP), (iii) Bose-Einstein Annealing Phase (BEAP), and (iv) Dynamical Equilibrium Phase (DEP). BAP and BEAP are simulated annealing searching procedures based on Boltzmann and Bose-Einstein distributions, respectively. DEP is also a simulated annealing search procedure, which is applied at the final temperature of the fourth phase, which can be seen as a second Bose-Einstein phase. MQP is a search process that ranges from extremely high to high temperatures, applying a very fast cooling process, and is not very restrictive to accept new solutions. However, BAP and BEAP range from high to low and from low to very low temperatures, respectively. They are more restrictive for accepting new solutions. DEP uses a particular heuristic to detect the stochastic equilibrium by applying a least squares method during its execution. MPSABBE parameters are tuned with an analytical method, which considers the maximal and minimal deterioration of problem instances. MPSABBE was tested with several instances of PFP, showing that the use of both distributions is better than using only the Boltzmann distribution on the classical SA. PMID:27413369
Optical analog of the Iordanskii force in a Bose-Einstein condensate
Leonhardt, U.; Oehberg, P.
2003-05-01
A vortex in a Bose-Einstein condensate generates the optical analog of the Aharonov-Bohm effect when illuminated with slow light. In contrast to the original Aharonov-Bohm effect the vortex will exchange forces with the light that leads to a measurable motion of the vortex.
On the occurrence and detectability of Bose-Einstein condensation in helium white dwarfs
Benvenuto, O.G.; Vito, M.A. De E-mail: adevito@fcaglp.unlp.edu.ar
2011-02-01
It has been recently proposed that helium white dwarfs may provide promising conditions for the occurrence of the Bose-Einstein condensation. The argument supporting this expectation is that in some conditions attained in the core of these objects, the typical De Broglie wavelength associated with helium nuclei is of the order of the mean distance between neighboring nuclei. In these conditions the system should depart from classical behavior showing quantum effects. As helium nuclei are bosons, they are expected to condense. In order to explore the possibility of detecting the Bose-Einstein condensation in the evolution of helium white dwarfs we have computed a set of models for a variety of stellar masses and values of the condensation temperature. We do not perform a detailed treatment of the condensation process but mimic it by suppressing the nuclei contribution to the equation of state by applying an adequate function. As the cooling of white dwarfs depends on average properties of the whole stellar interior, this procedure should be suitable for exploring the departure of the cooling process from that predicted by the standard treatment. We find that the Bose-Einstein condensation has noticeable, but not dramatic effects on the cooling process only for the most massive white dwarfs compatible with a helium dominated interior ( ≈ 0.50M{sub s}un) and very low luminosities (say, Log(L/L{sub s}un) < −4.0). These facts lead us to conclude that it seems extremely difficult to find observable signals of the Bose-Einstein condensation. Recently, it has been suggested that the population of helium white dwarfs detected in the globular cluster NGC 6397 is a good candidate for detecting signals of the Bose-Einstein condensation. We find that these stars have masses too low and are too bright to have an already condensed interior.
NASA Astrophysics Data System (ADS)
Minguzzi, A.; Succi, S.; Toschi, F.; Tosi, M. P.; Vignolo, P.
2004-06-01
The achievement of Bose-Einstein condensation in ultra-cold vapours of alkali atoms has given enormous impulse to the study of dilute atomic gases in condensed quantum states inside magnetic traps and optical lattices. High-purity and easy optical access make them ideal candidates to investigate fundamental issues on interacting quantum systems. This review presents some theoretical issues which have been addressed in this area and the numerical techniques which have been developed and used to describe them, from mean-field models to classical and quantum simulations for equilibrium and dynamical properties. After an introductory overview on dilute quantum gases, both in the homogeneus state and under harmonic or periodic confinement, the article is organized in three main sections. The first concerns Bose-condensed gases at zero temperature, with main regard to the properties of the ground state in different confinements and to collective excitations and transport in the condensate. Bose-Einstein-condensed gases at finite temperature are addressed in the next section, the main emphasis being on equilibrium properties and phase transitions and on dynamical and transport properties associated with the presence of the thermal cloud. Finally, the last section is focused on theoretical and computational issues that have emerged from the efforts to drive gases of fermionic atoms and boson-fermion mixtures deep into the quantum degeneracy regime, with the aim of realizing novel superfluids from fermion pairing. The attention given in this article to methods beyond standard mean-field approaches should make it a useful reference point for future advances in these areas.
De Souza, J.C.C.; Pires, M.O.C. E-mail: marcelo.pires@ufabc.edu.br
2014-03-01
We show that the galactic dark matter halo, considered composed of an axionlike particles Bose-Einstein condensate [6] trapped by a self-graviting potential [5], may be stable in the Thomas-Fermi approximation since appropriate choices for the dark matter particle mass and scattering length are made. The demonstration is performed by means of the calculation of the potential, kinetic and self-interaction energy terms of a galactic halo described by a Boehmer-Harko density profile. We discuss the validity of the Thomas-Fermi approximation for the halo system, and show that the kinetic energy contribution is indeed negligible.
NASA Astrophysics Data System (ADS)
Polo, J.; Ahufinger, V.; Mason, P.; Sridhar, S.; Billam, T. P.; Gardiner, S. A.
2015-05-01
We investigate a harmonically trapped two-component Bose-Einstein condensate within the miscible regime, close to its boundaries, for different ratios of effective intra- and interspecies interactions. We derive analytically a universal equation for the density around the different boundaries in one, two, and three dimensions, for both the coexisting and spatially separated regimes. We also present a general procedure to solve the Thomas-Fermi approximation in all three spatial dimensionalities, reducing the complexity of the Thomas-Fermi problem for the spatially separated case in one and three dimensions to a single numerical inversion. Finally, we analytically determine the frontier between the two different regimes of the system.
NASA Astrophysics Data System (ADS)
Opatrný, Tomáš; Kolář, Michal; Das, Kunal K.
2015-05-01
We propose a scheme for spin squeezing in the orbital motion of a Bose-Einstein condensate in a toroidal trap. A circular lattice couples two counterrotating modes and squeezing is generated by the nonlinear interaction spatially modulated at half the lattice period. By varying the amplitude and phase of the modulation, various cases of the twisting tensor can be directly realized, leading to different squeezing regimes. These include the one-axis twisting and two-axis countertwisting that are often discussed as the most important paradigms for spin squeezing. Our scheme naturally realizes the Lipkin-Meshkov-Glick model with the freedom to vary all its parameters simultaneously.
Perceived Attractiveness and Classroom Interactions
ERIC Educational Resources Information Center
Algozzine, Bob
1977-01-01
Adams and Cohen (1974) demonstrated that facial attractiveness was a salient factor in differential student-teacher interactions. This research investigates further the interaction between teachers and children perceived to be attractive or unattractive by those teachers. It was hypothesized that attractive children would exhibit more "positive,"…
Coherence and decoherence of excitations in a trapped Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Eitan, Rowen E.
A Bose-Einstein condensate of atomic vapor has proven in the past decade to be a simple enough system to follow theoretic predictions with great accuracy. Still, the control over all parameters gives a rich system, abundant with new physical phenom-ena together with the possibility of realizing clean physical models. The s-wave interactions between the atoms make this a generic tool for studying nonlinear physics. The excitations display a transition from a single particle nature to a many body nature. In this dissertation we study both dephasing and decoherence of excitations over a trapped condensate, with the intent of possibly overcoming these mechanisms. In the spectral domain we devise an echo method and suggest trap geometries with the aim of overcoming the less inherent inhomogeneous broadening and measuring the "natural line width" due to decoherence. By rapidly oscillating a condensate between different momentum states, we are able to overcome Doppler broadening and inhomogeneous broadening in the time domain. We also find a quantum enhancement of phonon scattering in contrast to the well known quantum suppression in the excitation of a phonon. The decoherence of a many-body state is one of the most interesting problems remaining in quantum mechanics. We study the coherent evolution of excitations, and their decoherence via collisions, towards the goal of understanding the process of decoherence of interacting many body systems, and perhaps controlling and suppressing it. Since we image both collided and non-collided population, we measure properties of the decoherence products and not only loss of the coherent population. For a rapidly oscillating condensate we find the damping products are shifted inwards in momentum space from the swave halo. We find an energy dependence of the decoherence rate in an elongated condensate, and explain this by use of radial modes. In optical lattices, where the spectrum is convex and energy conservation is impossible, we
Cosmological constraints on Bose-Einstein-condensed scalar field dark matter
NASA Astrophysics Data System (ADS)
Li, Bohua; Rindler-Daller, Tanja; Shapiro, Paul R.
2014-04-01
Despite the great successes of the cold dark matter (CDM) model in explaining a wide range of observations of the global evolution and the formation of galaxies and large-scale structure in the Universe, the origin and microscopic nature of dark matter is still unknown. The most common form of CDM considered to date is that of weakly interacting massive particles (WIMPs), but, so far, attempts to detect WIMPs directly or indirectly have not yet succeeded, and the allowed range of particle parameters has been significantly restricted. Some of the cosmological predictions for this kind of CDM are even in apparent conflict with observations (e.g., cuspy-cored halos and an overabundance of satellite dwarf galaxies). For these reasons, it is important to consider the consequences of different forms of CDM. We focus here on the hypothesis that the dark matter is comprised, instead, of ultralight bosons that form a Bose-Einstein condensate, described by a complex scalar field, for which particle number per unit comoving volume is conserved. We start from the Klein-Gordon and Einstein field equations to describe the evolution of the Friedmann-Robertson-Walker universe in the presence of this kind of dark matter. We find that, in addition to the radiation-, matter-, and Λ-dominated phases familiar from the standard CDM model, there is an earlier phase of scalar-field domination, which is special to this model. In addition, while WIMP CDM is nonrelativistic at all times after it decouples, the equation of state of Bose-Einstein condensed scalar field dark matter (SFDM) is found to be relativistic at early times, evolving from stiff (p ¯=ρ ¯) to radiationlike (p ¯=ρ ¯/3), before it becomes nonrelativistic and CDM-like at late times (p ¯=0). The timing of the transitions between these phases and regimes is shown to yield fundamental constraints on the SFDM model parameters, particle mass m, and self-interaction coupling strength λ. We show that SFDM is compatible with
Bose-Einstein Condensates with Spin-Orbit Interaction
Ho Tinlun; Zhang Shizhong
2011-10-07
Motivated by recent experiments carried out by Spielman's group at NIST, we study a general scheme for generating families of gauge fields, spanning the scalar, spin-orbit, and non-Abelian regimes. The NIST experiments, which impart momentum to bosons while changing their spin state, can in principle realize all these. In the spin-orbit regime, we show that a Bose gas is a spinor condensate made up of two non-orthogonal dressed spin states carrying different momenta. As a result, its density shows a stripe structure with a contrast proportional to the overlap of the dressed states, which can be made very pronounced by adjusting the experimental parameters.
Bose-Einstein correlations in pp and PbPb collisions with ALICE at the LHC
None
2016-07-12
We report on the results of identical pion femtoscopy at the LHC. The Bose-Einstein correlation analysis was performed on the large-statistics ALICE p+p at sqrt{s}= 0.9 TeV and 7 TeV datasets collected during 2010 LHC running and the first Pb+Pb dataset at sqrt{s_NN}= 2.76 TeV. Detailed pion femtoscopy studies in heavy-ion collisions have shown that emission region sizes ("HBT radii") decrease with increasing pair momentum, which is understood as a manifestation of the collective behavior of matter. 3D radii were also found to universally scale with event multiplicity. In p+p collisions at 7 TeV one measures multiplicities which are comparable with those registered in peripheral AuAu and CuCu collisions at RHIC, so direct comparisons and tests of scaling laws are now possible. We show the results of double-differential 3D pion HBT analysis, as a function of multiplicity and pair momentum. The results for two collision energies are compared to results obtained in the heavy-ion collisions at similar multiplicity and p+p collisions at lower energy. We identify the relevant scaling variables for the femtoscopic radii and discuss the similarities and differences to results from heavy-ions. The observed trends give insight into the soft particle production mechanism in p+p collisions and suggest that a self-interacting collective system may be created in sufficiently high multiplicity events. First results for the central Pb+Pb collisions are also shown. A significant increase of the reaction zone volume and lifetime in comparison to RHIC is observed. Signatures of collective hydrodynamics-like behavior of the system are also apparent, and are compared to model predictions.
Testing the Bose-Einstein Condensate dark matter model at galactic cluster scale
Harko, Tiberiu; Liang, Pengxiang; Liang, Shi-Dong; Mocanu, Gabriela E-mail: lpengx@mail2.sysu.edu.cn2 E-mail: gabriela.mocanu@ubbcluj.ro
2015-11-01
The possibility that dark matter may be in the form of a Bose-Einstein Condensate (BEC) has been extensively explored at galactic scale. In particular, good fits for the galactic rotations curves have been obtained, and upper limits for the dark matter particle mass and scattering length have been estimated. In the present paper we extend the investigation of the properties of the BEC dark matter to the galactic cluster scale, involving dark matter dominated astrophysical systems formed of thousands of galaxies each. By considering that one of the major components of a galactic cluster, the intra-cluster hot gas, is described by King's β-model, and that both intra-cluster gas and dark matter are in hydrostatic equilibrium, bound by the same total mass profile, we derive the mass and density profiles of the BEC dark matter. In our analysis we consider several theoretical models, corresponding to isothermal hot gas and zero temperature BEC dark matter, non-isothermal gas and zero temperature dark matter, and isothermal gas and finite temperature BEC, respectively. The properties of the finite temperature BEC dark matter cluster are investigated in detail numerically. We compare our theoretical results with the observational data of 106 galactic clusters. Using a least-squares fitting, as well as the observational results for the dark matter self-interaction cross section, we obtain some upper bounds for the mass and scattering length of the dark matter particle. Our results suggest that the mass of the dark matter particle is of the order of μ eV, while the scattering length has values in the range of 10{sup −7} fm.
Cosmological Constraints on Bose-Einstein-Condensed Scalar Field Dark Matter
NASA Astrophysics Data System (ADS)
Li, B.; Rindler-Daller, T.; Shapiro, P. R.
2013-10-01
We focus on the hypothesis that the darkmatter is comprised of ultralight bosons that form a Bose-Einstein Condensate (BEC), described by a complex scalar field. We calculate the evolution of the Friedmann-Robertson-Walker (FRW) universe in the presence of the BEC scalar field dark matter (SFDM).We find that, while WIMP CDM is non-relativistic at all times after it decouples, the equation of state of SFDM is found to be relativistic at early times, evolving from stiff (p¯ =r¯ ) to radiation-like (p¯ =r¯/3), before it becomes non-relativistic and CDM-like at late times (p¯ = 0. The stiff phase is a distinctive feature of our model. The timing of the transitions between these phases and regimes is shown to yield fundamental constraints on the SFDM model parameters, particle mass m and self-interaction coupling strength l . We show that SFDM is compatible with observations of the evolving background universe, by deriving the range of particle parameters required to match observations of the cosmic microwave background (CMB) and the abundances of the light elements produced by Big Bang nucleosynthesis (BBN), including Neff, the effective number of neutrino species, and the epoch of matter-radiation equality zeq. This yields m ≥ 2.4× 10-21eV/c2 and 9.5×10-19eV-1cm3 ≤l /(mc2)2 ≤ 4×10-17eV-1cm3. Indeed, our model can accommodate current observations in which Neff is higher at the BBN epoch than at zeq, probed by the CMB, which is otherwise unexplained by the standard CDM model involving WIMPs.
Impurity Crystal in a Bose-Einstein Condensate
Roberts, David C.; Rica, Sergio
2009-01-16
We investigate the behavior of impurity fields immersed in a larger condensate field in various dimensions. We discuss the localization of a single impurity field within a condensate and note the effects of surface energy. We derive the functional form of the attractive condensate-mediated interaction between two impurities. Generalizing the analysis to N impurity fields, we show that within various parameter regimes a crystal of impurity fields can form spontaneously in the condensate. Finally, the system of condensate and crystallized impurity structure is shown to have nonclassical rotational inertia, which is characteristic of superfluidity; i.e., the system can be seen to exhibit supersolid behavior.
Spin-momentum coupled Bose-Einstein condensates with lattice band pseudospins
Khamehchi, M. A.; Qu, Chunlei; Mossman, M. E.; Zhang, Chuanwei; Engels, P.
2016-01-01
The quantum emulation of spin-momentum coupling, a crucial ingredient for the emergence of topological phases, is currently drawing considerable interest. In previous quantum gas experiments, typically two atomic hyperfine states were chosen as pseudospins. Here, we report the observation of a spin-momentum coupling achieved by loading a Bose-Einstein condensate into periodically driven optical lattices. The s and p bands of a static lattice, which act as pseudospins, are coupled through an additional moving lattice that induces a momentum-dependent coupling between the two pseudospins, resulting in s–p hybrid Floquet-Bloch bands. We investigate the band structures by measuring the quasimomentum of the Bose-Einstein condensate for different velocities and strengths of the moving lattice, and compare our measurements to theoretical predictions. The realization of spin-momentum coupling with lattice bands as pseudospins paves the way for engineering novel quantum matter using hybrid orbital bands. PMID:26924575
On the nature of Bose-Einstein condensation enhanced by localization
Jaeck, Thomas; Pule, Joseph V.; Zagrebnov, Valentin A.
2010-10-15
In a previous paper we established that for the perfect Bose gas and the mean-field Bose gas with an external random or weak potential, whenever there is generalized Bose-Einstein condensation in the eigenstates of the single particle Hamiltonian, there is also generalized condensation in the kinetic-energy states. In these cases Bose-Einstein condensation is produced or enhanced by the external potential. In the present paper we establish a criterion for the absence of condensation in single kinetic-energy states and prove that this criterion is satisfied for a class of random potentials and weak potentials. This means that the condensate is spread over an infinite number of states with low kinetic-energy without any of them being macroscopically occupied.
Generalized Bose-Einstein condensation into multiple states in driven-dissipative systems.
Vorberg, Daniel; Wustmann, Waltraut; Ketzmerick, Roland; Eckardt, André
2013-12-13
Bose-Einstein condensation, the macroscopic occupation of a single quantum state, appears in equilibrium quantum statistical mechanics and persists also in the hydrodynamic regime close to equilibrium. Here we show that even when a degenerate Bose gas is driven into a steady state far from equilibrium, where the notion of a single-particle ground state becomes meaningless, Bose-Einstein condensation survives in a generalized form: the unambiguous selection of an odd number of states acquiring large occupations. Within mean-field theory we derive a criterion for when a single state and when multiple states are Bose selected in a noninteracting gas. We study the effect in several driven-dissipative model systems, and propose a quantum switch for heat conductivity based on shifting between one and three selected states.
Observation of shock waves in a large Bose-Einstein condensate
Meppelink, R.; Koller, S. B.; Vogels, J. M.; Straten, P. van der; Ooijen, E. D. van; Heckenberg, N. R.; Rubinsztein-Dunlop, H.; Haine, S. A.; Davis, M. J.
2009-10-15
We observe the formation of shock waves in a Bose-Einstein condensate containing a large number of sodium atoms. The shock wave is initiated with a repulsive blue-detuned light barrier, intersecting the Bose-Einstein condensate, after which two shock fronts appear. We observe breaking of these waves when the size of these waves approaches the healing length of the condensate. At this time, the wave front splits into two parts and clear fringes appear. The experiment is modeled using an effective one-dimensional Gross-Pitaevskii-like equation and gives excellent quantitative agreement with the experiment, even though matter waves with wavelengths two orders of magnitude smaller than the healing length are present. In these experiments, no significant heating or particle loss is observed.
Developing density functional theory for Bose-Einstein condensates. The case of chemical bonding
Putz, Mihai V.
2015-01-22
Since the nowadays growing interest in Bose-Einstein condensates due to the expanded experimental evidence on various atomic systems within optical lattices in weak and strong coupling regimes, the connection with Density Functional Theory is firstly advanced within the mean field framework at three levels of comprehension: the many-body normalization condition, Thomas-Fermi limit, and the chemical hardness closure with the inter-bosonic strength and universal Hohenberg-Kohn functional. As an application the traditional Heitler-London quantum mechanical description of the chemical bonding for homopolar atomic systems is reloaded within the non-linear Schrödinger (Gross-Pitaevsky) Hamiltonian; the results show that a two-fold energetic solution is registered either for bonding and antibonding states, with the bosonic contribution being driven by the square of the order parameter for the Bose-Einstein condensate density in free (gas) motion, while the associate wave functions remain as in classical molecular orbital model.
Gap solitons in spin-orbit-coupled Bose-Einstein condensates in optical lattices
NASA Astrophysics Data System (ADS)
Zhang, Yongping; Xu, Yong; Busch, Thomas
2015-04-01
While different ways to realize spin-orbit coupling in Bose-Einstein condensates exist, not all are currently experimentally implementable. Here we present a detailed study of gap solitons in a Bose-Einstein condensate with experimentally realizable spin-orbit coupling and discuss two cases relating to a spin-dependent parity symmetry. In the parity symmetric case, two families of fundamental gap solitons in the second linear energy gap are demonstrated with the opposite sign of the parity, with one family having single-humped densities and the other double-humped ones. In the case of broken parity symmetry, the fundamental modes manifest spin polarization. Both families possess an opposite sign of the spin polarization.
Superstripes and the excitation spectrum of a spin-orbit-coupled Bose-Einstein condensate.
Li, Yun; Martone, Giovanni I; Pitaevskii, Lev P; Stringari, Sandro
2013-06-01
Using Bogoliubov theory we calculate the excitation spectrum of a spinor Bose-Einstein condensed gas with an equal Rashba and Dresselhaus spin-orbit coupling in the stripe phase. The emergence of a double gapless band structure is pointed out as a key signature of Bose-Einstein condensation and of the spontaneous breaking of translational invariance symmetry. In the long wavelength limit the lower and upper branches exhibit, respectively, a clear spin and density nature. For wave vectors close to the first Brillouin zone, the lower branch acquires an important density character responsible for the divergent behavior of the structure factor and of the static response function, reflecting the occurrence of crystalline order. The sound velocities are calculated as functions of the Raman coupling for excitations propagating orthogonal and parallel to the stripes. Our predictions provide new perspectives for the identification of supersolid phenomena in ultracold atomic gases.
Dark matter as the Bose-Einstein condensation in loop quantum cosmology
NASA Astrophysics Data System (ADS)
Atazadeh, K.; Darabi, F.; Mousavi, M.
2016-06-01
We consider the FLRW universe in a loop quantum cosmological model filled with radiation, baryonic matter (with negligible pressure), dark energy, and dark matter. The dark matter sector is supposed to be of Bose-Einstein condensate type. The Bose-Einstein condensation process in a cosmological context by supposing it as an approximate first-order phase transition, has already been studied in the literature. Here, we study the evolution of the physical quantities related to the early universe description such as the energy density, temperature, and scale factor of the universe, before, during, and after the condensation process. We also consider in detail the evolution era of the universe in a mixed normal-condensate dark matter phase. The behavior and time evolution of the condensate dark matter fraction is also analyzed.
An efficient numerical method for computing dynamics of spin F = 2 Bose-Einstein condensates
Wang Hanquan
2011-07-01
In this paper, we extend the efficient time-splitting Fourier pseudospectral method to solve the generalized Gross-Pitaevskii (GP) equations, which model the dynamics of spin F = 2 Bose-Einstein condensates at extremely low temperature. Using the time-splitting technique, we split the generalized GP equations into one linear part and two nonlinear parts: the linear part is solved with the Fourier pseudospectral method; one of nonlinear parts is solved analytically while the other one is reformulated into a matrix formulation and solved by diagonalization. We show that the method keeps well the conservation laws related to generalized GP equations in 1D and 2D. We also show that the method is of second-order in time and spectrally accurate in space through a one-dimensional numerical test. We apply the method to investigate the dynamics of spin F = 2 Bose-Einstein condensates confined in a uniform/nonuniform magnetic field.
Bose-Einstein Condensate Coupled to a Nanomechanical Resonator on an Atom Chip
Treutlein, Philipp; Hunger, David; Camerer, Stephan; Haensch, Theodor W.; Reichel, Jakob
2007-10-05
We theoretically study the coupling of Bose-Einstein condensed atoms to the mechanical oscillations of a nanoscale cantilever with a magnetic tip. This is an experimentally viable hybrid quantum system which allows one to explore the interface of quantum optics and condensed matter physics. We propose an experiment where easily detectable atomic spin flips are induced by the cantilever motion. This can be used to probe thermal oscillations of the cantilever with the atoms. At low cantilever temperatures, as realized in recent experiments, the backaction of the atoms onto the cantilever is significant and the system represents a mechanical analog of cavity quantum electrodynamics. With high but realistic cantilever quality factors, the strong coupling regime can be reached, either with single atoms or collectively with Bose-Einstein condensates. We discuss an implementation on an atom chip.
Spin-momentum coupled Bose-Einstein condensates with lattice band pseudospins.
Khamehchi, M A; Qu, Chunlei; Mossman, M E; Zhang, Chuanwei; Engels, P
2016-02-29
The quantum emulation of spin-momentum coupling, a crucial ingredient for the emergence of topological phases, is currently drawing considerable interest. In previous quantum gas experiments, typically two atomic hyperfine states were chosen as pseudospins. Here, we report the observation of a spin-momentum coupling achieved by loading a Bose-Einstein condensate into periodically driven optical lattices. The s and p bands of a static lattice, which act as pseudospins, are coupled through an additional moving lattice that induces a momentum-dependent coupling between the two pseudospins, resulting in s-p hybrid Floquet-Bloch bands. We investigate the band structures by measuring the quasimomentum of the Bose-Einstein condensate for different velocities and strengths of the moving lattice, and compare our measurements to theoretical predictions. The realization of spin-momentum coupling with lattice bands as pseudospins paves the way for engineering novel quantum matter using hybrid orbital bands.
NASA Astrophysics Data System (ADS)
Pattinson, R. W.; Billam, T. P.; Gardiner, S. A.; McCarron, D. J.; Cho, H. W.; Cornish, S. L.; Parker, N. G.; Proukakis, N. P.
2013-01-01
We investigate the mean-field equilibrium solutions for a two-species immiscible Bose-Einstein condensate confined by a harmonic confinement with additional linear perturbations. We observe a range of equilibrium density structures, including ball and shell formations and axially or radially separated states, with a marked sensitivity to the potential perturbations and the relative atom number in each species. Incorporation of linear trap perturbations, albeit weak, are found to be essential to match the range of equilibrium density profiles observed in a recent 87Rb-133Cs Bose-Einstein condensate experiment [McCarron , Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.84.011603 84, 011603(R) (2011)]. Our analysis of this experiment demonstrates that sensitivity to linear trap perturbations is likely to be an important factor in interpreting the results of similar experiments in the future.
Structure formation in immiscible two-species Bose-Einstein condensates in perturbed harmonic traps
NASA Astrophysics Data System (ADS)
Pattinson, Robert; Parker, Nick; Proukakis, Nick; Liu, I.-Kang; Gou, Shih-Chuan; Gardiner, Simon; McCarron, Daniel; Cho, Hung-Wen; Cornish, Simon; Billam, Tom
2013-05-01
We investigate the mean-field equilibrium solutions for a trapped two-species 87Rb-133Cs immiscible Bose-Einstein condensate, and show that the density profiles observed in a recent Bose-Einstein experiment (D. J. McCarron et al. Phys. Rev. A 84, 011603 (2011)), which include ball and shell formations and axially/radially separated states, can be reproduced when accounting for weak linear perturbations. We also demonstrate the importance of the coupled growth of the two condensates by a simple finite temperature model which reveals such structures to be generally metastable in the presence of dissipation, with our findings confirmed by the more accurate Stochastic Projected Gross-Pitaevskii equation.
Dipole oscillations of a Bose-Einstein condensate in the presence of defects and disorder.
Albert, M; Paul, T; Pavloff, N; Leboeuf, P
2008-06-27
We consider dipole oscillations of a trapped dilute Bose-Einstein condensate in the presence of a scattering potential consisting either in a localized defect or in an extended disordered potential. In both cases the breaking of superfluidity and the damping of the oscillations are shown to be related to the appearance of a nonlinear dissipative flow. At supersonic velocities the flow becomes asymptotically dissipationless.
Continuous measurement of atom-number moments of a Bose-Einstein condensate by photodetection
Prataviera, G.A.; Oliveira, M.C. de
2004-07-01
We propose a measurement scheme that allows determination of even moments of a Bose-Einstein condensate (BEC) atom number, in a ring cavity, by continuous photodetection of an off-resonant quantized optical field. A fast cavity photocounting process limits the heating of atomic samples with a relatively small number of atoms, being convenient for BECs on microchip scale applications. The measurement back-action introduces a counting-conditioned phase damping, suppressing the condensate typical collapse and revival dynamics.
Excitations in a Nonequilibrium Bose-Einstein Condensate of Exciton Polaritons
Wouters, Michiel; Carusotto, Iacopo
2007-10-05
We develop a mean-field theory of the dynamics of a nonequilibrium Bose-Einstein condensate of exciton polaritons in a semiconductor microcavity. The spectrum of elementary excitations around the stationary state is analytically studied by means of a generalized Gross-Pitaevskii equation. A diffusive behavior of the Goldstone mode is found in the spatially homogeneous case and new features are predicted for the Josephson effect in a two-well geometry.
Modugno, M.; Tozzo, C.; Dalfovo, F.
2006-12-15
We theoretically investigate the dynamic properties of a Bose-Einstein condensate in a toroidal trap. A periodic modulation of the transverse confinement is shown to produce a density pattern due to parametric amplification of phonon pairs. By imaging the density distribution after free expansion one obtains (i) a precise determination of the Bogoliubov spectrum and (ii) a sensitive detection of quantized circulation in the torus. The parametric amplification is also sensitive to thermal and quantum fluctuations.
Bogoliubov-Cerenkov Radiation in a Bose-Einstein Condensate Flowing against an Obstacle
Carusotto, I.; Hu, S. X.; Collins, L. A.; Smerzi, A.
2006-12-31
We study the density modulation that appears in a Bose-Einstein condensate flowing with supersonic velocity against an obstacle. The experimental density profiles observed at JILA are reproduced by a numerical integration of the Gross-Pitaevskii equation and then interpreted in terms of Cerenkov emission of Bogoliubov excitations by the defect. The phonon and the single-particle regions of the Bogoliubov spectrum are, respectively, responsible for a conical wave front and a fan-shaped series of precursors.
Phase-Diffusion Dynamics in Weakly Coupled Bose-Einstein Condensates
Boukobza, Erez; Vardi, Amichay; Chuchem, Maya; Cohen, Doron
2009-05-08
We study the phase sensitivity of collisional phase diffusion between weakly coupled Bose-Einstein condensates, using a semiclassical picture of the two-mode Bose-Hubbard model. When weak coupling is allowed, zero relative phase locking is attained in the Josephson-Fock transition regime, whereas a {pi} relative phase is only locked in Rabi-Josephson point. Our analytic semiclassical estimates agree well with the numerical results.
Bose-Einstein distribution of money in a free-market economy. II
NASA Astrophysics Data System (ADS)
Kürten, K. E.; Kusmartsev, F. V.
2011-01-01
We argue about the application of methods of statistical mechanics to free economy (Kusmartsev F. V., Phys. Lett. A, 375 (2011) 966) and find that the most general distribution of money or income in a free-market economy has a general Bose-Einstein distribution form. Therewith the market is described by three parameters: temperature, chemical potential and the space dimensionality. Numerical simulations and a detailed analysis of a generic model confirm this finding.
Javanainen, Juha
2010-05-15
We study theoretically an atomic Bose-Einstein condensate in a double-well trap, both quantum-mechanically and classically, under conditions such that in the classical model an unstable equilibrium dissolves into large-scale oscillations of the atoms between the potential wells. Quantum mechanics alone does not exhibit such nonlinear dynamics, but measurements of the atom numbers in the potential wells may nevertheless cause the condensate to behave essentially classically.
Photon antibunching upon scattering by an atomic Bose-Einstein condensate
Ilichev, L. V. Chapovsky, P. L.
2010-05-15
Antibunching of photodetections from different modes is shown to arise when two quantized light modes are scattered by an atomic Bose-Einstein condensate. This effect appears because of the uncertainty in the position of the condensate wave function relative to the optical lattice formed by the light beams. It is shown how the information contained in the history of photodetections leads to a spatial localization of the condensate wave function.
Higbie, J; Stamper-Kurn, D M
2002-03-01
We consider a two-component atomic gas illumined by two intersecting laser beams which induce Raman coupling between the components. This spatially periodic coupling modifies the dispersion relation of the gas. Properties of a Bose-Einstein condensate of such a gas are strongly affected by this modification. Using the quasiparticle excitation spectrum derived from a Bogoliubov transformation, the Landau critical velocity is found to be anisotropic and can be widely tuned by varying properties of the dressing laser beams.
Connection between rotation and miscibility in a two-component Bose-Einstein condensate
Shimodaira, Takayuki; Saito, Hiroki; Kishimoto, Tetsuo
2010-07-15
A two-component Bose-Einstein condensate rotating in a toroidal trap is investigated. The topological constraint depends on the density distribution of each component along the circumference of the torus, and therefore the quantization condition on the circulation can be controlled by changing the miscibility using the Feshbach resonance. We find that the system exhibits a variety of dynamics depending on the initial angular momentum when the miscibility is changed.
Collision dynamics of skyrmions in a two-component Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Kaneda, Tomoya; Saito, Hiroki
2016-03-01
The dynamics of skyrmions in a two-component Bose-Einstein condensate is numerically investigated in the mean-field theory. When two skyrmions collide with each other, they are first united and then scattered into various states. For head-on collisions, skyrmions with unit winding number are scattered. The collision dynamics with an impact parameter are shown to depend on the relative phase. These dynamic processes are characterized by integer winding numbers.
Viscondi, T. F.; Furuya, K.; Oliveira, M. C. de
2009-07-15
The generalized purity is employed for investigating the process of coherence loss and delocalization of the Q function in the Bloch sphere of a two-mode Bose-Einstein condensate in a symmetrical double well with cross collision. Quantum phase transition of the model is signaled by the generalized purity as a function of an appropriate parameter of the Hamiltonian and the number of particles (N). A power-law dependence of the critical parameter with N is derived.
Storage of Spin Squeezing in a Two-Component Bose-Einstein Condensate
Jin, Guang-Ri; Kim, Sang Wook
2007-10-26
A simple scheme for storage of spin squeezing in a two-component Bose-Einstein condensate is investigated by considering rapidly turning-off the external field at a time that maximal spin squeezing occurs. We show that strong reduction of spin fluctuation can be maintained in a nearly fixed direction. We explain the underlying physics using the phase model and present analytical expressions of the maximal-squeezing time and the corresponding squeezing parameter.
Storage of spin squeezing in a two-component Bose-Einstein condensate.
Jin, Guang-Ri; Kim, Sang Wook
2007-10-26
A simple scheme for storage of spin squeezing in a two-component Bose-Einstein condensate is investigated by considering rapidly turning-off the external field at a time that maximal spin squeezing occurs. We show that strong reduction of spin fluctuation can be maintained in a nearly fixed direction. We explain the underlying physics using the phase model and present analytical expressions of the maximal-squeezing time and the corresponding squeezing parameter.
Energetically stable particlelike skyrmions in a trapped Bose-Einstein condensate.
Savage, C M; Ruostekoski, J
2003-07-01
We numerically show that a topologically nontrivial 3D Skyrmion can be energetically stable in a trapped two-component atomic Bose-Einstein condensate, for the parameters of 87Rb condensate experiments. The separate conservation of the two atomic species can stabilize the Skyrmion against shrinking to zero size, while drift of the Skyrmion due to the trap-induced density gradient can be prevented by rotation or by a laser potential.
Field effects on the vortex states in spin-orbit coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Xu, Liang-Liang; Liu, Yong-Kai; Feng, Shiping; Yang, Shi-Jie
2016-06-01
Multi-quantum vortices can be created in the ground state of rotating Bose-Einstein condensates with spin-orbit couplings. We investigate the effects of external fields, either a longitudinal field or a transverse field, on the vortex states. We reveal that both fields can effectively reduce the number of vortices. In the latter case we further find that the condensate density packets are pushed away in the horizontal direction and the vortices finally disappear to form a plane wave phase.
Josephson Effect in Trapped Spin-orbit Coupled Bose-Einstein Condensation
NASA Astrophysics Data System (ADS)
Tang, Wai Ho
Spin-orbit coupling (SOC) has given rise to many novel states of matter including topological insulators and superconductors. Recent experimental realization of SOC in neutral cold atom systems have opened a new avenue to study its effects in Bose-Einstein condensate. In this study, we discuss the Josephson-like mode in the spin-orbit coupled condensate, and study its decoherence due to thermal effect. We discuss experimental implications of our results.