Bulletin of the American Physical Society
2005 36th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 17–21, 2005; Lincoln, Nebraska
Session E2: Low Dimensional Quantum Gases and Quantum Mixtures |
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Chair: Nicholas P. Bigelow, University of Rochester Room: Burnham Yates Conference Center Ballroom II |
Thursday, May 19, 2005 8:00AM - 8:36AM |
E2.00001: Experimental study of a 1D Tonks-Girardeau gas Invited Speaker: I will describe our experiments with 1D Bose gases. We use a combination of conservative light traps to prepare and study atoms in 1D both near zero temperature and at finite temperature. We can scan across coupling regimes, including into the regime of the Tonks-Girardeau gas [1]. We have been able to test the exact 1D Bose gas theory [2,3] using several observables, including 1D energy, 1D cloud lengths, and the second order correlation function, g$^{(2)}$(0). \newline [1] T. Kinoshita, T. Wenger, and D. S. Weiss, Science 305, 1125 (2004). \newline [2] E.H. Lieb and W. Liniger, Phys. Rev. 130, 1605 (1963). \newline [3] M. Olshanii and V. Dunjko, Phys. Rev. Lett. 91, 090401 (2003). [Preview Abstract] |
Thursday, May 19, 2005 8:36AM - 9:12AM |
E2.00002: Atom-molecular oscillations of a Bose gas in an optical lattice Invited Speaker: A Bose gas in an optical lattice can undergo a quantum phase transition between a superfluid and a ``Mott insulator'' state [1]. We have created a Mott insulator state of $^{87}$Rb atoms in an optical lattice with a controllable number of atoms per site, and measured its stimulated Raman photoassociation spectrum. We found that higher density samples exhibited a two-peaked spectrum arising from photoassociation in sites with two and three atoms, respectively. The splitting between these peaks provides a measurement of the atom-molecule scattering length. Raman photoassociation of a sample with a central core of Mott insulator with two atoms per site induced macroscopic coherent oscillations between an atomic and a molecular gas, as predicted by Jaksch \textit{et al. }[2]. Our result implies that at the point of minimum atom number, we have created a molecular quantum gas with one molecule in each lattice site. In addition, we have carried out Bragg spectroscopy of the gas [3], and found evidence of a gap in the excitation spectrum of the insulating state. This work was carried out in collaboration with C. Ryu, Emek Yesilada, Xu Du, and Shoupu Wan. We acknowledge the support of the R.A. Welch Foundation, the N.S.F., and the D.O.E Quantum Optics Initiative. [1] Markus Greiner \textit{et al., }Nature \textbf{415}, 39 (2002). [2] D. Jaksch \textit{et al.}, Phys. Rev. Lett. \textbf{89}, 040402 (2002). [3] D. Van Oosten \textit{et al.}, cond-mat/0405492 (2004). [Preview Abstract] |
Thursday, May 19, 2005 9:12AM - 9:48AM |
E2.00003: Cold atom Fermi/Bose quantum liquid mixtures Invited Speaker: One of the intriguing avenues opened up by the advances in cold atom fermion cooling is the prospect of exploring fermion-boson quantum liquid mixtures in atom traps. Past experiments with condensed helium-3/helium-4 fluid mixtures, the only such mixtures accessible so far to table top experimentation, revealed an intricate phase diagram even though helium-3 remained normal (i.e. non-superfluid). However, strong-interaction effects greatly complicate any quantitative microscopic description of such striking phenomena as the phase separation of the helium-3 and helium-4 fluids. The helium-4 mediated interactions that are responsible for the separation were shown to be an order of magnitude weaker than calculated in lowest order perturbation. The Helium-3 mediated interactions, still attractive, can pair the helium-3 fluid into a superfluid, but at much lower temperatures. In comparison, the anticipated cold atom fermion-boson experiments could be amenable to first principle descriptions and their realizations would cover a much wider range of parameters. We will present insights from a theoretical study of the collective excitations of the simplest fermion-boson mixture: a single component fermion gas mixed in a with a cold atom Bose-Einstein condensate. We suggest that we can understand the dynamics of the onset of a phase separation, and we point out that retardation radically alters the nature of the mediated interaction if the Fermi-velocity exceeds the velocity of BEC-sound (not the regime of the helium mixtures). Even for mixtures in which the second fluid consists of only a single quantum particle, we find that the mediated interactions can give rise to non-trivial effects. [Preview Abstract] |
Thursday, May 19, 2005 9:48AM - 10:24AM |
E2.00004: Interacting Fermions in Optical Lattices Invited Speaker: Optical lattices are a powerful tool to create novel many-body quantum systems with ultra-cold atoms. They allow it to tune the role of interactions in the system or to change its dimensionality. The atoms inside an optical lattice experience a periodic potential which is formed by mutually perpendicular standing-wave laser fields. In this talk I will report on first experiments with a quantum degenerate two-component Fermi-gas in a three-dimensional optical lattice. We directly image the Fermi surface of the atoms in the lattice by turning off the optical lattice adiabatically. Due to the confining potential gradual filling of the lattice transforms the system from a normal state into a band insulator. The dynamics of the transition from a band insulator to a normal state is studied and the time scale is measured to be an order of magnitude larger than the tunnelling time in the lattice. Using a Feshbach resonance we tune the interaction between atoms in two different spin states, allowing us to dynamically induce a coupling between the lowest energy bands or to form molecules. [Preview Abstract] |
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