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 O3: Focus Session: Degenerate Gases in Reduced Dimension |
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Chair: Brett Esry, Kansas State University Room: Keller Building 104 |
Friday, May 30, 2008 8:00AM - 8:36AM |
O3.00001: The 2D Bose gas: observation of the BKT transition and the intermediate regime between thermal and superfluid. Invited Speaker: I will present experimental results on a Bose gas in a quasi-2D geometry, near the Berezinskii, Kosterlitz and Thouless (BKT) transition temperature. By measuring the 2D density profile and the coherence length of the gas, we identify different states of the gas. In particular, we observe that the gas exhibits a bimodal distribution without long range order. In this state, the gas in not superfluid, but presents a longer coherence length than the thermal cloud. Experimental evidence seems to indicate that we are observing the transition from this regime towards superfluidity (BKT transition). [Preview Abstract] |
Friday, May 30, 2008 8:36AM - 8:48AM |
O3.00002: Fractional Quantum Hall Effects with Bose-gases in Rotating Optical Lattice Potentials Nathan Gemelke, Edina Sarajlic, Steven Chu It has previously been noted that an analog to the fractional quantum-Hall (FQH) effect for two-dimensional electron gases can be produced with harmonically trapped and rotating neutral atoms. We report progress investigating FQH-like effects in the centrifugal limit of small, rotating, two-dimensional Bose gases. An ensemble of such systems is prepared in an optical lattice with locally rotating on-site potentials, produced by manipulation only of lattice beam optical phases. The non- rotating few-atom ground states are adiabatically transformed to higher angular momentum by applying a time-dependent sweep of rotation rate and deformation of the local lattice potential. Near the centrifugal limit, where the trap rotates at its vibration frequency, correlation is expected as a result of collisions. The onset of this behavior is probed by a combination of photoassociative transitions to bound molecules, and careful analysis of time-of-flight momentum distributions of atoms suddenly released from the lattice. [Preview Abstract] |
Friday, May 30, 2008 8:48AM - 9:00AM |
O3.00003: Effective Low-Dimensional Hamiltonian for Strongly Interacting Atoms in a Transverse Trap Jason Kestner, Luming Duan We consider an ultracold, dilute gas of two-component fermions strongly trapped along one or two dimensions. In a previous work [1], we have shown that near a Feshbach resonance, the excited modes of the transverse trap are not frozen out, even for very strong trapping. Now, we form an effective low-dimensional Hamiltonian by introducing a dressed molecule state comprising a superposition of the Feshbach molecule and atomic Cooper pairs in excited trap modes. The transverse physics is thus incorporated via the structure of this dressed molecule state. The dressed molecule is localized in all dimensions to less than the trap length scale, so, for a dilute gas, its structure is determined solely by the two-body physics. Thus, by matching the two-body bound state of the effective Hamiltonian with the exact two-body bound state, we are able to fix all the parameters in the effective Hamiltonian. This should provide a useful starting point for understanding the low-dimensional many-body physics when the gas is near its ground state configuration. [1] J.P. Kestner and L.-M. Duan, Phys. Rev. A 74, 053606 (2006). [Preview Abstract] |
Friday, May 30, 2008 9:00AM - 9:12AM |
O3.00004: Effects of tunneling on thermalization of quasi-one-dimensional gases Vladimir Yurovsky A many-body system, that does not approach thermal equilibrium, was realized in the quantum Newton's cradle experiment at Penn State [1], performed on an array of quasi-one-dimensional Bose gases in a two-dimensional optical lattice. This behavior reflects integrability of the Lieb-Liniger-McGuire model (see [2]), which can approximately describe the gas in each of the lattice tubes. Thermalization was observed in recent Penn State experiments [3] when the lattice depth is decreased. The present theoretical approach relates thermalization to the coupling of adjacent waveguides in the two-dimensional optical lattice due to tunneling of atoms. The analysis provides estimates of the thermalization rate and its dependence on the tunneling rate. The estimates are in agreement with the experimental results [3]. 1. T. Kinoshita, T. R. Wenger, and D. S. Weiss, Nature, Vol. 440, 900, (2006). 2. V. A. Yurovsky, M. Olshanii, and D. S. Weiss, Adv. At. Mol. Opt. Phys., Vol. 55, 61, (2008). 3. D. S. Weiss, private communication (2007). [Preview Abstract] |
Friday, May 30, 2008 9:12AM - 9:48AM |
O3.00005: Minimum Instances of Topological Matter in an Optical Plaquette Invited Speaker: We propose experimental schemes to create and probe minimum forms of different topologically ordered states in a plaquette of an optical lattice: Resonating Valence Bond, Laughlin and String condensed states. We show how to create anyonic excitations on top of these liquids and detect their fractional statistics. In addition, we propose a way to design a plaquette ring-exchange interaction, the building block Hamiltonian of a lattice topological theory. Our preparation and detection schemes combine different techniques already demonstrated in experiments with atoms in optical superlattices. [Preview Abstract] |
Friday, May 30, 2008 9:48AM - 10:00AM |
O3.00006: 1-D Mott insulator transition of a Bose-Einstein condensate Rachel Sapiro, Rui Zhang, Georg Raithel We experimentally demonstrate the superfluid to one-dimensional Mott-insulator transition of a $^{87}$Rb Bose-Einstein condensate. In the experiment, we apply a one-dimensional optical lattice, formed by two laser beams with a wavelength of 852~nm, to a three dimensional BEC in a shallow trap. We use Kapitza-Dirac scattering to precisely determine the depth of the optical lattice without knowledge of its exact geometry. It is found that the one-dimensional Mott insulator state is reached at a lattice depth of 30 recoil energies. We further study behavior specific to the one-dimensional case, including interference between pancake BECs in separate wells and dephasing behavior at the transition between the superfluid and Mott insulator states. [Preview Abstract] |
Friday, May 30, 2008 10:00AM - 10:12AM |
O3.00007: Charge density waves and off-diagonal order in the 1D Bose-Fermi-Hubbard model for fast fermions Alexander Mering, Michael Fleischhauer We discuss the Bose-Fermi-Hubbard model in 1D in the limit of fast (light) fermions. In this case, the fermions act as virtual quanta giving rise to an effective long-range interaction for the bosons, favouring a charge density wave (CDW) at $q=1/\rho_F $ at small bosonic hopping. We derive an effective theory predicting accurately the CDW amplitude if the mean-field backaction of the bosons is included in the free dynamics of the fermions. The analytic predictions are compared to numerical DMRG results giving evidence that a finite CDW is associated with exponentially decaying bosonic correlations thus questioning the existence of a supersolid phase. [Preview Abstract] |
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