Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session B3: Spinor BEC |
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Chair: Michael Chapman, Georgia Institute of Technology Room: 202 |
Tuesday, June 4, 2013 10:30AM - 10:42AM |
B3.00001: Collective excitations in spinor Bose-Einstein condensate G. Edward Marti, Ryan Olf, Sean Lourette, Andrew MacRae, Dan Stamper-Kurn The multiple broken symmetries in a ferromagnetic Bose-Einstein condensate lead to two Nambu-Goldstone bosons: a phonon and a magnon. A magnon --- a spin impurity excitation --- is a gapless mode with a quadratic dispersion relation. We introduce a new spin imaging technique to study the transport and dispersion of weak spin excitations in a $F=1$ ${}^{87}$Rb spinor condensates. We use this technique to measure the magnon mass, magnetic moment, and energy gap. [Preview Abstract] |
Tuesday, June 4, 2013 10:42AM - 10:54AM |
B3.00002: Dynamical and Topological Stability of Coreless Vortices in a Spin-1 $^{87}$Rb BEC Ryan Olf, G. Edward Marti, Sean Lourette, Andrew MacRae, Dan Stamper-Kurn The order parameter provides a powerful framework for understanding the elementary and topological excitations of a system near its ground state. Away from the ground state, a system's dynamics become increasingly important and distinguishing topological and dynamical effects can become difficult. Spin-1 Bose-Einstein condensates (BEC) admit rich dynamics and two distinct order parameter spaces with different topologies, making them a versatile platform for both dynamical and topological studies of the system both in and out of equilibrium. In this talk we discuss recent experiments done in our lab investigating the dynamics and topology of spin textures in Spin-1 $^{87}$Rb BEC. [Preview Abstract] |
Tuesday, June 4, 2013 10:54AM - 11:06AM |
B3.00003: Spinor dynamics in a $^{23}$Na spin-1 thermal Bose gas H.K. Pechkis, J. Wrubel, A. Schwettmann, P.F. Griffin, R. Barnett, E. Tiesinga, P.D. Lett We present experimental observations of coherent spin-changing collisions in a cold thermal spin-1 Bose gas of $^{23}$Na atoms. We observe clear oscillations in the m$_F$=0 spin population for the thermal gas for various magnetic field and different initial phases. Experimental results show that the population oscillations in a multi-spatial-mode thermal gas have the same behavior as those observed in a single-spatial-mode antiferromagnetic spinor Bose Einstein condensate. We demonstrate this by showing that the two situations are described by the same dynamical equations, with a factor of two change in the spin dependent interaction coefficient, which results from the change to particles with distinguishable momentum states in the thermal gas. We find quantitative agreement with the measured amplitude and period of the oscillations as a function of magnetic field for different initial spinor phases. We also extract a value of the spin dependent interaction coefficient that is in a good agreement with the theory. [Preview Abstract] |
Tuesday, June 4, 2013 11:06AM - 11:18AM |
B3.00004: Signature of effective three-body interactions on the dynamics of spin-1 atoms in an optical lattice Eite Tiesinga, Khan W. Mahmud We performed a theoretical study of the non-equilibrium dynamics of spin-1 bosons in an optical lattice after suddenly raising the lattice depth. The hamiltonian that describes the physics of such deep harmonic wells comprises of effective multi-body interactions arising from virtual excitations to higher bands. Spin-1 bosons are known to contain a spin-dependent coupling term which interconverts a pair of spin-0 bosons into a spin+1 and spin-1 bosons, and vice versa; the signature of which shows up in the population oscillations after our quench set up. We show that this expected spin mixing dynamics is influenced by the effective three-body interactions, and a frequency analysis of the oscillations clearly shows its signature. We treat both antiferromagnetic ($^{23}$Na) and ferromagnetic ($^{87}$Rb) condensates. The spin-1 bosonic case treated here is unique in the sense that the three-body effect is evident directly in the in-situ number oscillations in addition to the familiar coherence visibility. [Preview Abstract] |
Tuesday, June 4, 2013 11:18AM - 11:30AM |
B3.00005: Full Bloch Bose-Einstein condensates Azure Hansen, Justin T. Schultz, Nicholas P. Bigelow We create and characterize a spin texture in a spinor Bose-Einstein condensate (BEC) that, in analogy to the full Poincare laser beams of singular optics [1], covers the Bloch sphere. The time evolution of the full Bloch BEC spin texture allows us to access information about the Gouy phase in matter waves. This phase anomaly is an important and interesting topic in optics and has not yet been directly measured in atom optics. Using this system, we explore parallels between angular momenta in light and in atoms. To engineer the complex wavefunction of a BEC, we use a coherent Raman spin imprinting technique. This transfers phase, amplitude, and polarization properties from a set of laser beams onto the phase, amplitude, and spin of the BEC. \\[4pt] [1] A.M. Beckley, T.G. Brown, and M.A. Alonso, ``Full Poincare beams.'' Optics Express 18, 10777 (2010). [Preview Abstract] |
Tuesday, June 4, 2013 11:30AM - 11:42AM |
B3.00006: Persistent Currents in Spinor Condensates Scott Beattie, Stuart Moulder, Richard Fletcher, Zoran Hadzibabic We create and study persistent currents in a toroidal two-component Bose gas, consisting of~Rb-87 atoms in two different spin states. For a large spin-population imbalance we observe supercurrents persisting for over two minutes. However, we find that the supercurrent is unstable for spin polarization below a well-defined critical value. We also investigate the role of phase coherence between the two spin components and show that only the magnitude of the spin-polarization vector, rather than its orientation in spin space, is relevant for supercurrent stability [Phys. Rev. Lett. 110, 025301 (2013)]. [Preview Abstract] |
Tuesday, June 4, 2013 11:42AM - 11:54AM |
B3.00007: Measurement backaction on a spinor condensate from off-resonant light Steven Steinke, Swati Singh, Pierre Meystre, Keith Schwab, Mukund Vengalattore We study the quantum backaction of spin precession imaging measurements on a Bose-Einstein condensate by off-resonant light. Two main results are the derivation of a quantum jump operator describing the small, abrupt change in the spin state of the atoms caused by the detection of a single photon and a conditional stochastic master equation for the evolution of the condensate subject to a particular measurement record. We examine the implications of these backaction effects for magnetometry and also evaluate their utility in quantum state preparation. [Preview Abstract] |
Tuesday, June 4, 2013 11:54AM - 12:06PM |
B3.00008: Topological interface physics in spinor Bose-Einstein condensates Magnus Borgh, Janne Ruostekoski We present an experimentally viable scheme whereby the physics of coherent interfaces between topologically distinct regions can be studied in an atomic quantum gas~[1]. 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~[1,2]. 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 \emph{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.\\[4pt] [1] M.~O.~Borgh and J.~Ruostekoski, Phys.\ Rev.\ Lett.\ \textbf{109,} 015302 (2012)\\[0pt] [2] M.~O.~Borgh and J.~Ruostekoski, arXiv:1212.2147 (2012) [Preview Abstract] |
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