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Dan Stamperkurn - One of the best experts on this subject based on the ideXlab platform.
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spontaneously modulated spin textures in a dipolar spinor bose Einstein Condensate
Physical Review Letters, 2008Co-Authors: M Vengalattore, Sabrina Leslie, Jennie Guzman, Dan StamperkurnAbstract:Helical spin textures in a 87Rb F=1 spinor Bose-Einstein Condensate are found to decay spontaneously toward a spatially modulated structure of spin domains. The formation of this modulated phase is ascribed to magnetic dipolar interactions that energetically favor the short-wavelength domains over the long-wavelength spin helix. The reduction of dipolar interactions by a sequence of rf pulses results in a suppression of the modulated phase, thereby confirming the role of dipolar interactions in this process. This study demonstrates the significance of magnetic dipole interactions in degenerate 87Rb F=1 spinor gases.
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high resolution magnetometry with a spinor bose Einstein Condensate
Physical Review Letters, 2007Co-Authors: M Vengalattore, James Higbie, Sabrina Leslie, Jennie Guzman, Lorraine Sadler, Dan StamperkurnAbstract:We demonstrate a precise magnetic microscope based on direct imaging of the Larmor precession of a $^{87}\mathrm{Rb}$ spinor Bose-Einstein Condensate. This magnetometer attains a field sensitivity of $8.3\text{ }\text{ }\mathrm{pT}/{\mathrm{Hz}}^{1/2}$ over a measurement area of $120\text{ }\text{ }\ensuremath{\mu}{\mathrm{m}}^{2}$, an improvement over the low-frequency field sensitivity of modern SQUID magnetometers. The achieved phase sensitivity is close to the atom shot-noise limit, estimated as $0.15\text{ }\text{ }\mathrm{pT}/{\mathrm{Hz}}^{1/2}$ for a unity duty cycle measurement, suggesting the possibilities of spatially resolved spin-squeezed magnetometry. This magnetometer marks a significant application of degenerate atomic gases to metrology.
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high resolution magnetometry with a spinor bose Einstein Condensate
Physical Review Letters, 2007Co-Authors: M Vengalattore, James Higbie, Sabrina Leslie, Jennie Guzman, Lorraine Sadler, Dan StamperkurnAbstract:We demonstrate a precise magnetic microscope based on direct imaging of the Larmor precession of a 87Rb spinor Bose-Einstein Condensate. This magnetometer attains a field sensitivity of 8.3 pT/Hz1/2 over a measurement area of 120 microm2, an improvement over the low-frequency field sensitivity of modern SQUID magnetometers. The achieved phase sensitivity is close to the atom shot-noise limit, estimated as 0.15 pT/Hz1/2 for a unity duty cycle measurement, suggesting the possibilities of spatially resolved spin-squeezed magnetometry. This magnetometer marks a significant application of degenerate atomic gases to metrology.
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excitation of phonons in a bose Einstein Condensate by light scattering
Physical Review Letters, 1999Co-Authors: Dan Stamperkurn, A P Chikkatur, A Gorlitz, S Inouye, Subhadeep Gupta, David E Pritchard, Wolfgang KetterleAbstract:Stimulated small-angle light scattering was used to measure the structure factor of a Bose-Einstein Condensate in the phonon regime. The excitation strength for phonons was found to be significantly reduced from that of free particles, revealing the presence of correlated pair excitations and quantum depletion in the Condensate. The Bragg resonance line strength and line shift agreed with predictions for the homogeneous Bose gas using a local density approximation.
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superradiant rayleigh scattering from a bose Einstein Condensate
Science, 1999Co-Authors: S Inouye, Dan Stamperkurn, A P Chikkatur, David E Pritchard, J Stenger, Wolfgang KetterleAbstract:Rayleigh scattering off a Bose-Einstein Condensate was studied. Exposing an elongated Condensate to a single off-resonant laser beam resulted in the observation of highly directional scattering of light and atoms. This collective light scattering is caused by the coherent center-of-mass motion of the atoms in the Condensate. A directional beam of recoiling atoms was built up by matter wave amplification.
Wolfgang Ketterle - One of the best experts on this subject based on the ideXlab platform.
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Buffer-Gas Cooled Bose-Einstein Condensate
Physical Review Letters, 2009Co-Authors: S. Charles Doret, Wolfgang Ketterle, Colin B. Connolly, John M. DoyleAbstract:We report the creation of a Bose-Einstein Condensate using buffer-gas cooling, the first realization of Bose-Einstein condensation using a broadly general method which relies neither on laser cooling nor unique atom-surface properties. Metastable helium ((4)He*) is buffer-gas cooled, magnetically trapped, and evaporatively cooled to quantum degeneracy. 10(11) atoms are initially trapped, leading to Bose-Einstein condensation at a critical temperature of 5 microK and threshold atom number of 1.1 x 10(6). This method is applicable to a wide array of paramagnetic atoms and molecules, many of which are impractical to laser cool and impossible to surface cool.
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coreless vortex formation in a spinor bose Einstein Condensate
Physical Review Letters, 2003Co-Authors: Yongil Shin, David Kielpinski, D E Pritchard, Wolfgang KetterleAbstract:: Coreless vortices were phase imprinted in a spinor Bose-Einstein Condensate. The three-component order parameter of F=1 sodium Condensates held in a Ioffe-Pritchard magnetic trap was manipulated by adiabatically reducing the magnetic bias field along the trap axis to zero. This distributed the Condensate population across its three spin states and created a spin texture. Each spin state acquired a different phase winding which caused the spin components to separate radially.
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vortex nucleation in a stirred bose Einstein Condensate
Physical Review Letters, 2001Co-Authors: C Raman, J R Aboshaeer, J M Vogels, Wolfgang KetterleAbstract:We studied the nucleation of vortices in a Bose-Einstein Condensate stirred by a laser beam. The vortex cores were observed using time-of-flight absorption imaging. Depending on the stirrer size, either discrete resonances or a broad response was visible as the stir frequency was varied. Stirring beams small compared to the Condensate size generated vortices below the critical rotation frequency for the nucleation of surface modes, suggesting a local mechanism of generation. In addition, we observed the centrifugal distortion of the Condensate due to the rotating vortex lattice and found evidence for bent vortices.
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excitation of phonons in a bose Einstein Condensate by light scattering
Physical Review Letters, 1999Co-Authors: Dan Stamperkurn, A P Chikkatur, A Gorlitz, S Inouye, Subhadeep Gupta, David E Pritchard, Wolfgang KetterleAbstract:Stimulated small-angle light scattering was used to measure the structure factor of a Bose-Einstein Condensate in the phonon regime. The excitation strength for phonons was found to be significantly reduced from that of free particles, revealing the presence of correlated pair excitations and quantum depletion in the Condensate. The Bragg resonance line strength and line shift agreed with predictions for the homogeneous Bose gas using a local density approximation.
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superradiant rayleigh scattering from a bose Einstein Condensate
Science, 1999Co-Authors: S Inouye, Dan Stamperkurn, A P Chikkatur, David E Pritchard, J Stenger, Wolfgang KetterleAbstract:Rayleigh scattering off a Bose-Einstein Condensate was studied. Exposing an elongated Condensate to a single off-resonant laser beam resulted in the observation of highly directional scattering of light and atoms. This collective light scattering is caused by the coherent center-of-mass motion of the atoms in the Condensate. A directional beam of recoiling atoms was built up by matter wave amplification.
Massimo Inguscio - One of the best experts on this subject based on the ideXlab platform.
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magnetic dipolar interaction in a bose Einstein Condensate atomic interferometer
Physical Review Letters, 2008Co-Authors: Marco Fattori, Massimo Inguscio, Giacomo Roati, B Deissler, C Derrico, Matteo Zaccanti, M Jonalasinio, L Santos, Giovanni ModugnoAbstract: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.
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anderson localization of a non interacting bose Einstein Condensate
Nature, 2008Co-Authors: Giacomo Roati, L Fallani, Michele Modugno, Marco Fattori, C Derrico, Matteo Zaccanti, Giovanni Modugno, C. Fort, Massimo InguscioAbstract:Anderson localization of waves in disordered media was originally predicted fifty years ago, in the context of transport of electrons in crystals. The phenomenon is much more general and has been observed in a variety of systems, but never directly for matter waves. The authors use a non-interacting Bose–Einstein Condensate of ultracold atoms to study Anderson localization. The effect is clearly demonstrated through investigations of the transport properties and spatial and momentum distributions. The highly controllable nature of the system may render it useful for investigations of the interplay between disorder and interaction, and to uncover exotic quantum phases. Anderson localization of waves in disordered media was originally predicted1 fifty years ago, in the context of transport of electrons in crystals2. The phenomenon is much more general3 and has been observed in a variety of systems, including light waves4,5. However, Anderson localization has not been observed directly for matter waves. Owing to the high degree of control over most of the system parameters (in particular the interaction strength), ultracold atoms offer opportunities for the study of disorder-induced localization6. Here we use a non-interacting Bose–Einstein Condensate to study Anderson localization. The experiment is performed with a one-dimensional quasi-periodic lattice—a system that features a crossover between extended and exponentially localized states, as in the case of purely random disorder in higher dimensions. Localization is clearly demonstrated through investigations of the transport properties and spatial and momentum distributions. We characterize the crossover, finding that the critical disorder strength scales with the tunnelling energy of the atoms in the lattice. This controllable system may be used to investigate the interplay of disorder and interaction (ref. 7 and references therein), and to explore exotic quantum phases8,9.
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atom interferometry with a weakly interacting bose Einstein Condensate
Physical Review Letters, 2008Co-Authors: Marco Fattori, Massimo Inguscio, Michele Modugno, Giacomo Roati, C Derrico, Matteo Zaccanti, M Jonalasinio, Giovanni ModugnoAbstract: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.
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atom interferometry with a weakly interacting bose Einstein Condensate
Physical Review Letters, 2008Co-Authors: Marco Fattori, Massimo Inguscio, C Derrico, Matteo Zaccanti, M Jonalasinio, M Modugno, G Roati, Giovanni ModugnoAbstract: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 $^{39}\mathrm{K}$ Condensate trapped in an optical lattice, where Bloch oscillations are forced by gravity. The fine-tuning of the scattering length down to $0.1\text{ }\text{ }{a}_{0}$ 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.
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39K Bose-Einstein Condensate with tunable interactions.
Physical Review Letters, 2007Co-Authors: Giacomo Roati, Massimo Inguscio, Michele Modugno, Matteo Zaccanti, C. D'errico, Jacopo Catani, Andrea SimoniAbstract:We produce a Bose-Einstein Condensate of 39K atoms. Condensation of this species with a naturally small and negative scattering length is achieved by a combination of sympathetic cooling with 87Rb 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 39K Condensate is interesting for future experiments requiring a weakly-interacting Bose gas.
R Grimm - One of the best experts on this subject based on the ideXlab platform.
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two dimensional bose Einstein Condensate in an optical surface trap
Physical Review Letters, 2004Co-Authors: D Rychtarik, B Engeser, H C Nagerl, R GrimmAbstract:We report on the creation of a two-dimensional Bose-Einstein Condensate of cesium atoms in a gravito-optical surface trap. The Condensate is produced a few microm above a dielectric surface on an evanescent-wave atom mirror. After evaporative cooling by all-optical means, expansion measurements for the tightly confined vertical motion show energies well below the vibrational energy quantum. The presence of a Condensate is observed in two independent ways by a magnetically induced collapse at negative scattering length and by measurements of the horizontal expansion.
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crossover from a molecular bose Einstein Condensate to a degenerate fermi gas
Physical Review Letters, 2004Co-Authors: M Bartenstein, A Altmeyer, Stefan J Riedl, Selim Jochim, Cheng Chin, Hecker J Denschlag, R GrimmAbstract:We demonstrate a reversible conversion of a 6Li2 molecular Bose-Einstein Condensate to a degenerate Fermi gas of atoms by adiabatically crossing a Feshbach resonance. By optical in situ imaging, we observe a smooth change of the cloud size in the crossover regime. On the Feshbach resonance, the ensemble is strongly interacting and the measured cloud size is 75(7)% of the one of a noninteracting zero-temperature Fermi gas. The high Condensate fraction of more than 90% and the adiabatic crossover suggest our Fermi gas to be cold enough to form a superfluid.
Tiberiu Harko - One of the best experts on this subject based on the ideXlab platform.
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Slowly rotating Bose Einstein Condensate galactic dark matter halos, and their rotation curves
SpringerOpen, 2018Co-Authors: Xiaoyue Zhang, Tiberiu Harko, Man Ho Chan, Shi-dong Liang, Chun Sing LeungAbstract:Abstract If dark matter is composed of massive bosons, a Bose–Einstein condensation process must have occurred during the cosmological evolution. Therefore galactic dark matter may be in a form of a Condensate, characterized by a strong self-interaction. We consider the effects of rotation on the Bose–Einstein Condensate dark matter halos, and we investigate how rotation might influence their astrophysical properties. In order to describe the Condensate we use the Gross–Pitaevskii equation, and the Thomas–Fermi approximation, which predicts a polytropic equation of state with polytropic index $$n=1$$ n=1 . By assuming a rigid body rotation for the halo, with the use of the hydrodynamic representation of the Gross–Pitaevskii equation we obtain the basic equation describing the density distribution of the rotating Condensate. We obtain the general solutions for the condensed dark matter density, and we derive the general representations for the mass distribution, boundary (radius), potential energy, velocity dispersion, tangential velocity and for the logarithmic density and velocity slopes, respectively. Explicit expressions for the radius, mass, and tangential velocity are obtained in the first order of approximation, under the assumption of slow rotation. In order to compare our results with the observations we fit the theoretical expressions of the tangential velocity of massive test particles moving in rotating Bose–Einstein Condensate dark halos with the data of 12 dwarf galaxies and the Milky Way, respectively
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Bose-Einstein Condensate general relativistic stars
Physical Review D, 2012Co-Authors: Pierre-henri Chavanis, Tiberiu HarkoAbstract:We analyze the possibility that due to their superfluid properties some compact astrophysical objects may contain a significant part of their matter in the form of a Bose-Einstein Condensate. To study the Condensate we use the Gross-Pitaevskii equation, with arbitrary non-linearity. By introducing the Madelung representation of the wave function, we formulate the dynamics of the system in terms of the continuity equation and of the hydrodynamic Euler equations. The non-relativistic and Newtonian Bose-Einstein gravitational Condensate can be described as a gas, whose density and pressure are related by a barotropic equation of state. In the case of a Condensate with quartic non-linearity, the equation of state is polytropic with index one. In the framework of the Thomas-Fermi approximation the structure of the Newtonian gravitational Condensate is described by the Lane-Emden equation, which can be exactly solved. The case of the rotating Condensate is also discussed. General relativistic configurations with quartic non-linearity are studied numerically with both non-relativistic and relativistic equations of state, and the maximum mass of the stable configuration is determined. Condensates with particle masses of the order of two neutron masses (Cooper pair) and scattering length of the order of 10-20 fm have maximum masses of the order of 2 M_sun, maximum central density of the order of 0.1-0.3 10^16 g/cm^3 and minimum radii in the range of 10-20 km. In this way we obtain a large class of stable astrophysical objects, whose basic astrophysical parameters (mass and radius) sensitively depend on the mass of the condensed particle, and on the scattering length. We also propose that the recently observed neutron stars with masses in the range of 2-2.4 M_sun are Bose-Einstein Condensate stars.
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can dark matter be a bose Einstein Condensate
arXiv: Astrophysics, 2007Co-Authors: Christian G Boehmer, Tiberiu HarkoAbstract:We consider the possibility that the dark matter, which is required to explain the dynamics of the neutral hydrogen clouds at large distances from the galactic center, could be in the form of a Bose-Einstein Condensate. To study the Condensate we use the non-relativistic Gross-Pitaevskii equation. By introducing the Madelung representation of the wave function, we formulate the dynamics of the system in terms of the continuity equation and of the hydrodynamic Euler equations. Hence dark matter can be described as a non-relativistic, Newtonian Bose-Einstein gravitational Condensate gas, whose density and pressure are related by a barotropic equation of state. In the case of a Condensate with quartic non-linearity, the equation of state is polytropic with index $n=1$. To test the validity of the model we fit the Newtonian tangential velocity equation of the model with a sample of rotation curves of low surface brightness and dwarf galaxies, respectively. We find a very good agreement between the theoretical rotation curves and the observational data for the low surface brightness galaxies. The deflection of photons passing through the dark matter halos is also analyzed, and the bending angle of light is computed. The bending angle obtained for the Bose-Einstein Condensate is larger than that predicted by standard general relativistic and dark matter models. Therefore the study of the light deflection by galaxies and the gravitational lensing could discriminate between the Bose-Einstein Condensate dark matter model and other dark matter models.
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Can dark matter be a Bose-Einstein Condensate?
Journal of Cosmology and Astroparticle Physics, 2007Co-Authors: Tiberiu HarkoAbstract:We consider the possibility that the dark matter which is required to explain the dynamics of the neutral hydrogen clouds at large distances from the galactic centre could be in the form of a Bose–Einstein Condensate. To study the Condensate we use the non-relativistic Gross–Pitaevskii equation. By introducing the Madelung representation of the wavefunction, we formulate the dynamics of the system in terms of the continuity equation and of the hydrodynamic Euler equations. Hence dark matter can be described as a non-relativistic, Newtonian Bose–Einstein gravitational Condensate gas, whose density and pressure are related by a barotropic equation of state. In the case of a Condensate with quartic non-linearity, the equation of state is polytropic with index n = 1. In the framework of the Thomas–Fermi approximation the structure of the Newtonian gravitational Condensate is described by the Lane–Emden equation, which can be exactly solved. General relativistic configurations with quartic non-linearity are studied, by numerically integrating the structure equations. The basic parameters (mass and radius) of the Bose–Einstein Condensate dark matter halos sensitively depend on the mass of the condensed particle and of the scattering length. To test the validity of the model we fit the Newtonian tangential velocity equation of the model with a sample of rotation curves of low surface brightness and dwarf galaxies, respectively. We find a very good agreement between the theoretical rotation curves and the observational data for the low surface brightness galaxies. The deflection of photons passing through the dark matter halos is also analysed, and the bending angle of light is computed. The bending angle obtained for the Bose–Einstein Condensate is larger than that predicted by standard general relativistic and dark matter models. The angular radii of the Einstein rings are obtained in the small angle approximation. Therefore the study of the light deflection by galaxies and the gravitational lensing could discriminate between the Bose–Einstein Condensate dark matter model and other dark matter models.