Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session U6: Vortices and Solitons |
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Chair: Peter Engels, Washington State University Room: Garden 4 |
Friday, June 8, 2012 10:30AM - 10:42AM |
U6.00001: Phase-Dependent Interactions of Bright Matter-Wave Solitons Paul Dyke, Sidong Lei, Randall Hulet We investigate the interaction of bright matter-wave solitons with a thin repulsive barrier. The solitons are formed from a Bose-Einstein condensate of $^7$Li atoms confined in quasi-1D by a focused laser beam. We use the broad Feshbach resonance for $^7$Li in the $|1,1\rangle$ state to tune the scattering length through zero to small negative values to produce bright matter-wave solitons with atom numbers close to the critical number for collapse. The barrier is generated by a near-resonant cylindrically focused laser beam that perpendicularly bisects the trapping beam. By adjusting the barrier potential, the soliton can either be split in two, transmitted or reflected. We apply a phase imprinting laser beam to one arm of the split soliton to study phase dependent interactions. We also investigate the transmission and reflection probabilities as a function of the strength of non-linear interactions which are tuned via the Feshbach resonance. [Preview Abstract] |
Friday, June 8, 2012 10:42AM - 10:54AM |
U6.00002: Interacting Bright Solitons in Trapped BECs: Mean-Field Theory and Way Beyond William Reinhardt Bright multi-soliton trains have been experimentally observed in harmonic traps,\footnote{K. E. Strecker \textit{et. al.,} Nature \textbf{417},150 (2002).} in experiments made especially difficult by the fact that a too-bright soliton (or ground state of an attractive BEC) will self destruct in 3D. These are fascinating systems as, as recently pointed out,\footnote{A. I. Streltsov \textit{et. al}., Phys. Rev. Lett. \textbf{106}, 240401 (2011).} usual mean-field descriptions via the NLSE (or GP) equation, will often fail, as many-body effects may play a crucial role. Here we discuss 4 regimes of the statics and dynamics of double-bright-soliton systems by giving an overview of the full energy correlation diagram in a two (non-linear) mode description. 1) Strongly trapped soliton pairs are found to be quite well described by GP, and also via two mode, dynamics, up-holding prior theoretical analysis of existing experiment.\footnote{Strecker, op. sit.} Separated soliton pairs may be: 2) Schr\"{o}dinger cats; 3) fully fragmented; or, 4) decohering\footnote{Streltsov, op. sit.} wave packets if followed via two-mode dynamics, using coherent mean-field (GP) initial conditions, and end up producing states of controllable partial entanglement. [Preview Abstract] |
Friday, June 8, 2012 10:54AM - 11:06AM |
U6.00003: Physical and Algebraic Origins of the Reflectionless Property of the Bogoliubov-de-Gennes-sine-Gordon Equation Around a Soliton Albert Albert Kamanzi, Zaijong Hwang, Maxim Olshanii We analyze the reflectionless property of the so-called Bogoliubov-de-Gennes-sine-Gordon (BdG-sG) equation---a Sine-Gordon equation that has been linearized around a single soliton solution. We demonstrate that the absence of reflection is necessary for the original nonlinear soliton be transparent for the small breathers. On the other hand, we show that the BdG-sG equation is equivalent to the P\"{o}schl-Teller (PT) potential at transparency, whose transparency, in turn, originates from a SUSY structure of the PT Hamiltonian. Our study provides yet another example of a connection between the Supersymmetric Quantum Mechanics\footnote{E. Witten, Nucl. Phys. B 188, 513 (1981)} and integrable partial differential equations, in addition to the known examples of the Lax operators for the Korteweg-de Vries, sine-Gordon, and Nonlinear Schr\"{o}dinger equations that are shown to a have a SUSY structure for some few-solitonic solutions.\footnote{C. V. Sukumar, 1986 J. Phys. A 19, 2297 (1986); A. Koller and M. Olshanii, Phys. Rev. E 84, 066601 (2011)} [Preview Abstract] |
Friday, June 8, 2012 11:06AM - 11:18AM |
U6.00004: Dynamic Kosterlitz-Thouless transition in 2D Bose mixtures of ultra-cold atoms Ludwig Mathey, Kenneth Guenter, Jean Dalibard, Anatoli Polkovnikov We propose a realistic experiment to demonstrate a dynamic Kosterlitz-Thouless transition in ultra-cold atomic gases in two dimensions. With a numerical implementation of the Truncated Wigner Approximation we simulate the time evolution of several correlation functions, which can be measured via matter wave interference. We demonstrate that the relaxational dynamics is well-described by a real-time renormalization group approach, and argue that these experiments can guide the development of a theoretical framework for the understanding of critical dynamics. [Preview Abstract] |
Friday, June 8, 2012 11:18AM - 11:30AM |
U6.00005: Origins of bright soliton transparency to Bogoliubov quasi-particles Zaijong Hwang, Andrew Koller, Maxim Olshanii Bogoliubov quasi-particles can pass through a one-dimensional bright soliton without reflection at all energies.\footnote{D. J. Kaup, Phys. Rev. A {\bf 42}, 5689 (1990).} Reflectionless properties of this kind usually originate from a supersymmetric structure of the corresponding Hamiltonian.\footnote{E. Witten, Nucl. Phys. B {\bf 188}, 513 (1981).}$^,$\footnote{C. V. Sukumar, J. Phys. A {\bf 18}, 2917 (1985).} However, we give a strong indication that in this case\footnotemark[1], the mathematical mechanism enabling full spectrum transparency of a scattering object does not fall into any of the conventional paradigms. [Preview Abstract] |
Friday, June 8, 2012 11:30AM - 11:42AM |
U6.00006: Observation of Topologically Stable 2D Skyrmions in an Antiferromagnetic Spinor Bose-Einstein Condensate Jaeyoon Choi, Woo Jin Kwon, Sang Won Seo, Yong-il Shin We report the creation and time evolution of two-dimensional (2D) skyrmion excitations in quasi-2D polar Bose-Einstein condensate of F=1 23Na atoms, where the 2D skyrmion is topologically protected.\footnote{J. Choi, W. J. Kwon, and Y. Shin, Physical Review Letters 108, 035301 (2012).} Spin rotation method was used for imprinting the skyrmion spin textures in a controllable manner. The skyrmion was observed to be stable on a short time scale of a few tens of ms but to dynamically deform its shape and eventually decay to a uniform spin texture. The decay dynamics involves breaking the polar phase inside the condensate without having topological charge density flow through the boundary of the finite-sized sample. We discuss the possible formation of half-quantum vortices in the deformation process. [Preview Abstract] |
Friday, June 8, 2012 11:42AM - 11:54AM |
U6.00007: On the dynamics of dark-bright and dark-dark solitons in two-component BECs JiaJia Chang, Chris Hamner, Peter Engels We report on experiments investigating the in-trap dynamics of novel solitonic structures resulting from a counterflow induced modulational instability in two-component $^{87}$Rb BECs. Different types of solitons, including trains of dark-bright solitons and vector dark-dark solitons, are reliably produced for different boundary conditions. The dark-bright solitons are observed to oscillate in-trap with a frequency far below the confining harmonic trap frequency. The vector dark-dark solitons show interesting dynamics during which they periodically change their structure. Current and ongoing results of our experiment will be discussed. [Preview Abstract] |
Friday, June 8, 2012 11:54AM - 12:06PM |
U6.00008: Pinning and manipulation of vortex cores in Bose-Einstein condensates Kali Wilson, E. Carlo Samson, Zachary Newman, Brian P. Anderson We demonstrate the ability to reproducibly generate, pin, and then manipulate vortex cores in highly oblate Bose-Einstein condensates (BECs). Piezoelectric transducer-controlled mirrors are used to swipe two blue-detuned laser beams across the BEC such that two vortices of opposite circulation are generated, with each pinned to a laser beam. The beams are then used to position the cores within the condensate. Using additional pinning potentials, this procedure may be scaled to larger numbers of pinned vortices and will be useful for generating arbitrary vortex distributions for studies of superfluid dynamics and vortex interactions. [Preview Abstract] |
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