Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session Q2: Bose-Einstein Condensates |
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Chair: J. Thywissen, University of Toronto Room: Gilmer Hall 130 |
Friday, May 22, 2009 8:00AM - 8:12AM |
Q2.00001: Phase Space Dynamics in an Antiferromagnetic Spinor Condensate Yingmei Liu, Eduardo Gomez, Stephen Maxwell, Lincoln Turner, Eite Tiesinga, Paul Lett Spinor condensates of F=1 sodium atoms display rich spin dynamics due to the antiferromagnetic nature of the interactions in this system. We make a continuous and minimally destructive measurement of the spin dynamics on a single evolving spinor condensate. This technique provides a sharp signature of a magnetically tuned boundary in phase space between the oscillating and running phase solutions. In recent experiments we have been able to track and observe the time evolution of atom number fluctuations, which contains a signature of the crossing of this boundary in phase space. We also introduce a phenomenological model to describe the observed energy dissipation. This allows us to investigate phase space dynamics during spin mixing in the condensate. [Preview Abstract] |
Friday, May 22, 2009 8:12AM - 8:24AM |
Q2.00002: Probe momentum distribution of a quasi-2d condensate using condensate focusing Shihkuang Tung, Giacomo Lamporesi, Eric Cornell A Bose-Einstein condensate is created in a TOP trap, then loaded into a 1D optical lattice. The optical lattice slices the condensate into several quasi-2D condensates. Using a selective microwave pumping scheme, we are able to select one slice of condensate and suddenly turn off interactions. We then focus [I. Shvarchuck et al, PRL 89,270404 (2002)] the selected condensate slice in two dimensions to image the momentum distribution below and above the BKT transition temperature. [Preview Abstract] |
Friday, May 22, 2009 8:24AM - 8:36AM |
Q2.00003: Three-Compoment Coreless Vortices in a Spinor BEC L. Suzanne Leslie, Azure Hansen, Kevin Wright, Nick Bigelow We present experimental results of three-component coreless vortices with winding number $w_i = \left(0,1,2\right)$ created in the $F=2$ manifold of $^{87}$Rb using an optical vortex coupling technique. Examples of vortices across a range of relative spatial distributions and spin state populations will be shown, and their vorticity confirmed through interference. [Preview Abstract] |
Friday, May 22, 2009 8:36AM - 8:48AM |
Q2.00004: Measuring the rates of spontaneous vortex formation in highly oblate Bose-Einstein condensates Tyler Neely, Edward Samson, Ashton Bradley, Matthew Davis, Brian Anderson By studying the dynamics of the Bose-Einstein condensation transition in highly oblate ($\sim $11:1 aspect ratio) traps, we have measured the dependence of spontaneous vortex formation on BEC growth rate, extending our previous experimental and numerical observations of spontaneous vortex formation in weakly oblate ($\sim $2:1 aspect ratio) traps [1]. Our condensation procedure in these highly oblate traps allows us to create BECs over a large range of growth times, from approximately 200 ms to over 2 s. By characterizing vortex formation vs. BEC growth rate, and comparing experimental and numerical results, the Kibble-Zurek mechanism for topological defect formation may be quantitatively studied in our system. [1] C.N. Weiler, T.W. Neely, D.R. Scherer, A.S. Bradley, M.J. Davis, and B.P. Anderson., \textit{Nature} \textbf{455}, 948 (2008). [Preview Abstract] |
Friday, May 22, 2009 8:48AM - 9:00AM |
Q2.00005: Splitting a Bose-Einstein Condensate in Two Translating Traps B. Sun, M.S. Pindzola, F. Robicheaux Motivated by an earlier proposal of splitting a one dimensional atomic wave packet using two translating traps (see M. Zhang et al., PRL {\bf 97}, 070403 (2006)), we report results of simulating the splitting dynamics for a three dimensional Bose-Einstein condensate at zero temperature. Different from the single atom case where the population in one of the traps shows full oscillations as a function of the translating velocity, we find that such oscillations are damped as the translating velocity decreases. The damping mechanism is attributed to the formation of solitons which decay to vortex rings and cuase complicated flow patterns to damp the population oscillations. The damping effect is more evident as the interaction strength increases. Therefore, the condensate can only be split by 50/50 in the adiabatically translating regime. Our conclusions are supported by simulations with N = 5400 and N = 54000 $^{87}$Rb atoms. [Preview Abstract] |
Friday, May 22, 2009 9:00AM - 9:12AM |
Q2.00006: Induced interaction and crystallization of impurity fields in a Bose-Einstein condensate David Roberts, Sergio Rica We model the behavior of N impurity classical fields immersed in a larger Bose-Einstein condensate by N+1 coupled nonlinear Schrodinger equations in 1, 2, and 3 dimensions. We discuss the stability of the uniform miscible system and show the importance of surface tension for self-localization of the impurities. We derive analytically the behavior of the attractive tail of impurity-impurity interaction due to the mediating effect of the underlying condensate. Assuming all impurities interact with the same strength, we numerically explore the phase diagram which contains four phases, namely i) where all fields are miscible; ii) where the impurities are miscible with each other but phase separate from the condensate as a single bubble; iii) where the impurities phase separate from the condensate and form a crystalline structure within a bubble; and iv) where localized impurities stay miscible within the condensate. Finally, we argue that the crystalline phases maintain a nonclassical rotational inertia, and hence have properties reminiscent of a supersolid. [Preview Abstract] |
Friday, May 22, 2009 9:12AM - 9:24AM |
Q2.00007: A buffer-gas cooled BEC of metastable $^4$He S. Charles Doret, Colin B. Connolly, Wolfgang Ketterle, John M. Doyle We report the first creation of a BEC (of metastable helium, $^4$He$^*$) using buffer-gas cooling, without the use of laser cooling. $10^{11}$ $^4$He $^*$ atoms are produced via RF-discharge and magnetically trapped at an initial temperature of 400 mK in an anit-Helmholtz quadrupole field. These atoms are evaporatively cooled into the ultracold regime and transferred to a tightly confining superconducting QUIC trap with trap frequencies $\omega_{axial}$ = 2$\pi$ x 210 Hz and $\omega_{radial}$ = 2$\pi$ x 2500 Hz. Further cooling is achieved by driving transitions with resonant RF radiation. The transition temperature is reached at $\sim$ 5 $\mu$K with approximately $10^6$ atoms. The cloud is detected via phase-contrast imaging at 1083 nm, either in-situ or in time-of-flight. [Preview Abstract] |
Friday, May 22, 2009 9:24AM - 9:36AM |
Q2.00008: Structure and Collapse of a Dipolar Bose-Einstein Condensate Ryan Wilson, Shai Ronen, John Bohn A Bose-Einstein condensate formed of dipolar particles is known to be unstable against collapse if the attractive part of the dipolar interaction is strong enough. Here we explore the limits of this stability, with special attention to the possibiliity of the condensate collapsing locally rather than collapsing as a whole toward the center of the trap. We explicitly connect local collapse to the presence of low-energy ``roton-like'' modes, and we propose experiments that could probe this local collapse. [Preview Abstract] |
Friday, May 22, 2009 9:36AM - 9:48AM |
Q2.00009: Solving Coupled Gross--Pitaevskii Equations on a Cluster of PlayStation 3 Computers Mark Edwards, Jeffrey Heward, C.W. Clark At Georgia Southern University we have constructed an 8+1--node cluster of Sony PlayStation 3 (PS3) computers with the intention of using this computing resource to solve problems related to the behavior of ultra--cold atoms in general with a particular emphasis on studying bose--bose and bose--fermi mixtures confined in optical lattices. As a first project that uses this computing resource, we have implemented a parallel solver of the coupled time--dependent, one--dimensional Gross--Pitaevskii (TDGP) equations. These equations govern the behavior of dual-- species bosonic mixtures. We chose the split--operator/FFT to solve the coupled 1D TDGP equations. The fast Fourier transform component of this solver can be readily parallelized on the PS3 cpu known as the Cell Broadband Engine (CellBE). Each CellBE chip contains a single 64--bit PowerPC Processor Element known as the PPE and eight ``Synergistic Processor Element'' identified as the SPE's. We report on this algorithm and compare its performance to a non--parallel solver as applied to modeling evaporative cooling in dual--species bosonic mixtures. [Preview Abstract] |
Friday, May 22, 2009 9:48AM - 10:00AM |
Q2.00010: The Two-Mode Approximation in a Realistic Bose-Josephson Junction in a $^{85}$Rb/$^{87}$Rb BEC Mixture Jeffrey Heward, Mark Edwards, C.W. Clark We have studied the behavior of an experimentally realistic Bose- Einstein condensate (BEC) mixture subjected to a double-well potential. The mixture studied consists of $^{87}$Rb and $^{85} $Rb held in an optical trap with an external magnetic field that enables tuning of the $^{85}$Rb--$^{85}$Rb scattering length. This system, without the external double--well potential, has been implemented at JILA [S.B.\ Papp, et al, Phys.Rev.Lett.\ {\bf 101}, 040402 (2008)]. A double--well potential can be added to this system by applying another pair of lasers as was done in a previous experiment for single condensates [M.\ Albiez, et al, Phys.\ Rev.\ Lett.\ {\bf 95}, 010402 (2005)]. We have used the Variable Tunneling Model (VTM) within the two--mode approximation to search for novel condensate mixture behavior in this experimentally accessible system. Possible behaviors include Bose--Josephson oscillations and macroscopic quantum self--trapping as described in a recent paper [I.\ Satija, et al, arXiv:0811.1921v1 [quant-ph]]. We compare the behavior as predicted by the two--mode VTM with the solution obtained by integrating the coupled Gross--Pitaevskii equations. We propose some new experiments designed to observe these novel phenomena. [Preview Abstract] |
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