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 K2: Focus Session: Ultracold Dipolar Gases |
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Chair: Ed Eyler, University of Connecticut Room: Kern Building 112 |
Thursday, May 29, 2008 2:00PM - 2:36PM |
K2.00001: Ultracold dense gas of heteronuclear deeply bound molecules Invited Speaker: The preparation of a dense ultracold polar molecular sample is a long standing goal of AMO physics. Polar molecules have bright prospects as systems with anisotropic interactions, for precision measurements and for quantum information science. One approach towards this goal is to combine Feshbach molecule creation in heteronuclear quantum gases with coherent optical deexcitation schemes and thereby produce an ultracold dense gas of heteronuclear molecules in deeply bound vibrational levels where the heteronuclear molecules exhibit a significant dipole moment. We report about a key step along this route. Starting from an ultracold dense gas of heteronuclear $^{40}$K$^{87}$Rb Feshbach molecules, we coherently transfer these molecules into a vibrational level of the ground-state molecular potential bound by $>10$\,GHz. We thereby increase the binding energy and the expected dipole moment of the $^{40}$K$^{87}$Rb molecules by more than four orders of magnitude in a single transfer step. While dipolar effects are currently not observable yet, the presented technique can be extended to access much more deeply bound vibrational levels and ultimately those exhibiting a significant dipole moment. The preparation of an ultracold quantum gas of polar molecules might therefore come within experimental reach. [Preview Abstract] |
Thursday, May 29, 2008 2:36PM - 2:48PM |
K2.00002: Universal Dipolar Scattering Christopher Ticknor We explore the impact of the short range interaction on the scattering of ground state polar molecules, and study the transition from a weak to strong dipolar scattering over an experimentally reasonable range of energies and electric field values. In the strong dipolar limit, the scattering scales with respect to a dimensionless quantity defined by mass, induced dipole moment, and collision energy. The scaling has implications for all quantum mechanical dipolar scattering, and therefore this universal dipolar scaling provides estimates of scattering cross sections for any dipolar system. Furthermore the universal scattering regime will readily be achieved with polar molecules at ultracold temperatures. [Preview Abstract] |
Thursday, May 29, 2008 2:48PM - 3:00PM |
K2.00003: Fermionic stabilization and density-wave ground state of a polar condensate. Omjyoti Dutta, Rina Kanamoto, Pierre Meystre We examine the stability of a trapped dipolar condensate mixed with a single-component fermion gas at $T=0$ in a pancake and cigar shaped trap. Whereas the density wave state in dipolar condensates with small s-wave interaction are unstable towards collapse, we find that the admixture of fermions can significantly stabilize them, depending on the strength of the boson-fermion interaction. [Preview Abstract] |
Thursday, May 29, 2008 3:00PM - 3:12PM |
K2.00004: Role of exchange energy in a trapped dipolar Fermi gas Takahiko Miyakawa, Takaaki Sogo, Han Pu We consider a system of quantum degenerate spin polarized fermions in a harmonic oscillator trap at zero temperature that mutually interact via dipole-dipole forces. We examine the ground state properties by use of a variational Wigner function to describe the deformation and compression of the Fermi gas in phase space. The exchange energy of dipolar interaction is shown to cause the deformation of Fermi surface. We also show that the exchange energy plays a crucial role in the stability of the system. [Preview Abstract] |
Thursday, May 29, 2008 3:12PM - 3:48PM |
K2.00005: Expansion and Dipolar Collapse of a Quantum Ferrofluid Invited Speaker: I will report on the realization of a chromium Bose-Einstein condensate (BEC) in the regime of strong dipolar interaction\footnote{T. Lahaye et al. Nature 448, 672 (2007)} by using a magnetic Feshbach resonance to suppress the isotropic contact interaction. In this way, the anisotropic magnetic dipole-dipole interaction between $^{52}$Cr atoms, which possess extraordinarily large magnetic moments, becomes comparable in strength to the contact interaction and can even be dominant in the condensate. We examine the system by observing the change in the expansion of the condensate when the s-wave scattering length is reduced close to the resonance. In the strongly dipolar regime, we even observe a suppression of the inversion of ellipticity during the expansion that is often considered the ``smoking gun'' evidence of Bose-Einstein condensation. The expansion dynamics is described by superfluid hydrodynamic equations where dipole-dipole interaction terms are included, similar to the way classical ferrofluids can be described by including such terms in classical hydrodynamics. When the contact interaction is reduced further by going even closer to the resonance, such that the s-wave scattering length becomes smaller than a critical value, we observe the collapse of the condensate due to the dipole-dipole interaction\footnote{T. Koch et al. arXiv:cond-mat 0710.3643 to be published in Nature physics}. Since the interaction is anisotropic, this critical value depends on the trap geometry. The condensate can be stabilized against dipolar collapse by trapping it in a pancake shaped trap such that we are able to tune the scattering length to zero and thus to generate a purely dipolar BEC. [Preview Abstract] |
Thursday, May 29, 2008 3:48PM - 4:00PM |
K2.00006: Ultra-cold polar molecules in an optical trap Eric Hudson, Nathan Gilfoy, Stephan Falke, David DeMille We have recently confined ultra-cold RbCs molecules in an optical trap. Currently, these molecules are in high-lying vibrational levels of the a$^3\Sigma^+$ ground electronic state. Inelastic collision rates of these molecules with both Rb and Cs atoms have been determined for individual vibrational levels, across an order of magnitude of binding energies. A simple model for the collision process is shown to accurately reproduce the observed scattering rates. We are currently implementing a state transfer process, previously demonstrated in our lab, to transfer these molecules into the X$^1\Sigma^+(v = 0)$ absolute ground state, which possesses a large electric dipole moment ($\mu \approx$ 1.3 Debye). We will report on our recent measurements of ultra-cold inelastic molecular collisions as well as our progress towards the trapping of absolute ground state polar molecules. [Preview Abstract] |
Thursday, May 29, 2008 4:00PM - 4:12PM |
K2.00007: Single photon nonlinearities using arrays of cold polar molecules Renuka Rajapakse, Timothy Bragdon, Ana Maria Rey, Susanne Yelin We model single photon nonlinearities via the dipole-dipole interaction of cold polar molecules. A manifold of protected symmetric eigenstates is used as basis for optical quantum computation. Decoherence occurs in this system because of non-symmetric interaction and phonon dispersion. We discuss the feasibility of this system in optical quantum computation processing as an element of a controlled phase gate. [Preview Abstract] |
Thursday, May 29, 2008 4:12PM - 4:24PM |
K2.00008: Bound-bound Spectroscopy of Ultracold K40-Rb87 Molecules Kang-Kuen Ni, Silke Ospelkaus, Avi Pe'er, Josh Zirbel, Brian Neyenhuis, Marcio Miranda, Svetlana Kotochigova, Paul Julienne, Jun Ye, Deborah Jin We have recently demonstrated coherent optical transfer of KRb Feshbach molecules to a more deeply bound vibrational state. This transfer relied on an extensive search for a suitable intermediate state of KRb* as well as precision two-photon spectroscopy of target vibrational levels in the electronic ground-state KRb. We will present results of the KRb and KRb* spectroscopy as well as our progress toward creation of degenerate KRb polar molecules. [Preview Abstract] |
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