Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session C2: Focus Session: Vortices and Solitons |
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Chair: Zachary Dutton, BBN Technologies Room: Kern Building 112 |
Wednesday, May 28, 2008 2:00PM - 2:36PM |
C2.00001: Soliton formation during the cooling, merging and splitting of BECs Invited Speaker: Bose-Einstein Condensates are a powerful tool for the study of nonlinear dynamics. In our experiments we investigate the formation and dynamics of dark solitons in a variety of different settings. First, we observe soliton trains as a result of quantum shock (dispersive shock) during the merging of two BECs. Second, when a BEC is split into two parts by a repulsive barrier, a transition from sound formation to shock generation and solitons is observed with increasing barrier strength. Third, we also observe soliton formation during the creation of a BEC when the transition from non-condensed atoms to a BEC is crossed sufficiently rapidly. In this talk I will describe our ongoing experiments investigating such dynamics. [Preview Abstract] |
Wednesday, May 28, 2008 2:36PM - 2:48PM |
C2.00002: Spontaneous vortices in Bose-Einstein condensate formation: comparison of experiment and theory Tyler Neely, Chad Weiler, David Scherer, Ashton Bradley, Matthew Davis, Brian P. Anderson By evaporative cooling of an atomic gas through the Bose-Einstein condensation transition, we have experimentally observed and characterized the spontaneous creation of vortices in BECs during the transition. We have also observed spontaneous formation of vortices in BECs through numerical simulations of the BEC transition using theoretical methods based on the Stochastic Gross-Pitaevskii equation formalism. Our experimental and theoretical results show excellent quantitative agreement. Furthermore, our results are qualitatively consistent with the Kibble-Zurek mechanism for topological defect formation in a phase transition. A quantitative comparison of our experimental and numerical observations will be presented. [Preview Abstract] |
Wednesday, May 28, 2008 2:48PM - 3:00PM |
C2.00003: Thermal melting of two dimensional finite vortex lattice Leslie Baksmaty, Uzi Landman, Han Pu We present a two dimensional study of a vortex lattice using the self-consistent Hartree-Fock-Bogoliubov formalism within the Popov approximation. Our physical model is a rotating trapped condensate with a tight axial confinement. At constant rotation we solve for the equilibrium configuration of successively higher temperatures until all the vortices have disappeared from the system and the condensate fraction becomes very small. We observe discontinuities in thermodynamic quantities, such as chemical potential, as temperature is raised, which are closely correlated with sudden changes in the structure of the vortex lattice and the sudden loss of vortices to the surrounding thermal cloud. As well as being directly relevant to the finite vortex lattices in trapped gases, this work could have implications for the physics of Neutron stars, high temperature superconductors and studies of structural phase transitions in general. [Preview Abstract] |
Wednesday, May 28, 2008 3:00PM - 3:12PM |
C2.00004: Inducing vortices in a Bose-Einstein condensate using light beams with orbital angular momentum Waseem Bakr, Jonathon Gillen, Amy Peng, Johannes Brachmann, Markus Greiner We excite vortex states in a Rb-87 BEC using coherent transfer of angular momentum from light to atoms. The transfer is achieved by a Raman transition between the two hyperfine ground states using a Gaussian beam and a holographically generated vortex beam. The arbitrary phase pattern imprinted onto the beam by the hologram is used to produce vortices with arbitrary charge and orientation. In particular, we demonstrate the controlled generation of a vortex anti-vortex pair and use atom interferometry to verify the creation of the expected phase pattern in the condensate. [Preview Abstract] |
Wednesday, May 28, 2008 3:12PM - 3:48PM |
C2.00005: Vortices in Rotating Optical Lattices Invited Speaker: A collection of ultracold atoms subject to a spatially periodic potential energy can exhibit many types of behavior analogous to electrons moving in a crystal lattice. One of the most remarkable correspondences occurs with atoms in a corotating two-dimensional optical lattice and electrons confined in two-dimensions in the presence of a strong magnetic field. In both cases, the remarkable features of the fractional quantum Hall effect emerge. The means that atoms in a rotating optical lattice can contain circulation and quantum vortices and, if the lattice is rotating sufficiently rapidly, can support exotic highly-correlated quantum states. In this talk I will provide a few perspectives on the exciting possibilities that atomic physics is now offering in this area, and present some results showing the effects of the quantization of circulation, the apperance of vortices, and some of the novel features of quantum phase transitions in these systems. [Preview Abstract] |
Wednesday, May 28, 2008 3:48PM - 4:00PM |
C2.00006: Vortex lattices of bosons in deep rotating lattices Daniel Goldbaum, Erich Mueller We study vortex-lattice phases for a Bose gas trapped in a rotating optical lattice near the Mott-Hubbard transition. Unlike the case of shallow lattices, the physics in this regime is dominated by the strong on-site interaction between bosons. We find a series of first-order structural transitions between square lattices where vortices are pinned with their cores on plaquettes/sites. We discuss connections between these vortex structures and the Hofstadter butterfly spectrum of free particles on a rotating lattice. We also investigate vortex configurations in a harmonic trap, where superfluid and Mott phases can coexist in a shell structure [1]. \newline \newline [1] D. Goldbaum and E. Mueller, \emph{Vortex lattices of bosons in deep rotating lattices}, arXiv.org:0710.1090 (2007). [Preview Abstract] |
Wednesday, May 28, 2008 4:00PM - 4:12PM |
C2.00007: Generation of complex spin textures in a Raman-coupled spinor BEC K.C. Wright, L.S. Leslie, N.P. Bigelow We demonstrate the controlled creation of complex spin and vortex states of a spinor condensate, using spatially varying Raman-detuned laser pulses to control the internal and external angular momentum of the condensate. By applying several combinations of optical modes and pulse patterns, we illustrate the versatility of this technique for creating a range of physically interesting multicomponent coreless vortex states. We also show that it is possible to generate coherent superpositions of such vortex states, and use the resulting interference patterns to confirm the presence of quantized vortices. [Preview Abstract] |
Wednesday, May 28, 2008 4:12PM - 4:24PM |
C2.00008: Engineering of Quantum Entangled Dark Solitons on One-Dimensional Optical Lattices R.V. Mishmash, I. Danshita, C. W. Clark, L.D. Carr Using density and phase engineering techniques, we create quantum entangled dark solitons on a one-dimensional Bose-Hubbard lattice. This is accomplished numerically by employing a number-conserving time-evolving block decimation routine to simulate the Bose-Hubbard Hamiltonian. We show that when deep in the superfluid regime of the ground state phase diagram, solitons can be created with lifetimes on the order of tens of tunneling times. The soliton decay is purely due to quantum effects which we characterize with a complete set of quantum measures that include quantum depletion, von Neumann and generalized quantum entropies, and number fluctuations. Comparisons are made to the Bogoliubov theory which predicts quantum depletion into an anomalous mode that fills in the soliton. Our full quantum treatment allows us to go beyond the Bogoliubov approximation and explicitly calculate the time dependence of the distribution of the system's natural orbitals as well as their exact spatial form. [Preview Abstract] |
Wednesday, May 28, 2008 4:24PM - 4:36PM |
C2.00009: Density engineering of an oscillating soliton/vortex ring in a Bose-Einstein condensate Shahar Levy, Itay Shomroni, Elias Lahoud, Jeff Steinhauer We study solitons in a Bose-Einstein condensate by engineering a density minimum on the healing length scale, using a far off-resonant laser beam. This results in a pair of counterpropagating solitons, which is the low collisional energy version of the celebrated matter wave interference pattern [M. R. Andrews et al., Science 275, 637 (1997)]. The solitons subsequently evolve into a pair of periodic soliton/vortex rings. We image the vortex rings and solitons in-situ on the healing length scale. This stable periodic evolution is in sharp contrast to the behavior of previous experiments in which the solitons decay irreversibly into vortex rings via the snake instability. The periodic oscillation between two qualitatively different forms seems to be a rare phenomenon in nature. We explain this phenomenon in terms of conservation of mass and energy in a narrow condensate. [Preview Abstract] |
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