Bulletin of the American Physical Society
38th Annual Meeting of the Division of Atomic, Molecular, and Optical Physics
Volume 52, Number 7
Tuesday–Saturday, June 5–9, 2007; Calgary, Alberta, Canada
Session G1: Optical Lattices |
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Chair: K. O'Hara, Penn State University Room: TELUS Convention Centre Macleod BC |
Thursday, June 7, 2007 8:00AM - 8:36AM |
G1.00001: Cold atoms and the 2D Bose-Hubbard model Invited Speaker: Cold atoms in optical lattices provide new avenues for studying iconic condensed matter problems. Using an initially Bose condensed sample of $^{87}$Rb atoms, we implement the 2D Bose-Hubbard model (one intense lattice beam partitions the system into an ensemble of 2D systems; the remaining 2D lattice potential determines the constants in the Bose-Hubbard model). This model has a superfluid-insulator transition, and this work focuses on the insulating phase. We carefully control the lattice lattice parameters, the loading procedure, and the total atom number and we measure momentum distributions which agree quantitatively with the predictions of theory (for a homogenous system). In our images, we also measure correlations in the atom-shot noise which given information regarding the spatial extend of the system. The correlation signal changes as expected as the insulating region develops. [Preview Abstract] |
Thursday, June 7, 2007 8:36AM - 9:12AM |
G1.00002: Orbital phases of the lattice $p$-band bosons Invited Speaker: Motivated by rapid developments in optical lattices, in this talk, I will introduce a new model system, which might previously have seemed academic or excessively special but now seems experimentally accessible. It is a system of ultracold bosonic atoms in the optical lattice $p$-band, which has also been studied by several other groups independently. I will discuss three aspects of the system: (a) the p-band lifetime, (b) novel order, and (c) detectable signatures. For (a), I will suggest ideas on how to keep the $p$-band population from decaying to the lowest $s$-band. For (b), the system will be shown to display interesting phases that I believe are new in both condensed matter and atomic physics, including a phase of non-zero momentum Bose-Einstein condensation and transversely staggered orbital current order in a cubic lattice and a phase of quantum orbital stripe order in a frustrated triangular optical lattice. In the triangular case, an orbital angular momentum moment is formed on each site exhibiting a stripe order both in the superfluid and Mott-insulating phases. For (c), unique signatures of each of the new phases will be predicted, which I believe can be proved or disproved by possible future experiments such as the time-of-flight. [Preview Abstract] |
Thursday, June 7, 2007 9:12AM - 9:48AM |
G1.00003: Atomic and molecular quantum gases in an optical lattice Invited Speaker: We report on recent progress in preparing and manipulating ultracold atomic and molecular ensembles in a 3D optical lattice. Starting from an atomic $^{87}$Rb condensate which is adiabatically loaded into a 3D optical lattice we can control the state and dynamics of the gas on the quantum level with the help of static magnetic fields, radio-frequency and laser radiation and a Feshbach resonance. For example, we can produce a pure molecular ensemble of Rb$_2$ Feshbach molecules in the lattice [1] and can coherently transfer it to a more deeply molecular bound state via STIRAP [2] or radio-frequency transitions. Besides possible applications for investigating molecular collisions and producing ultracold molecules in the vibrational ground state, this can also be used for spectroscopic precision measurements of molecular levels. Besides studying chemically bound molecules, optical lattices also allow for forming a novel kind of stable bound state of two atoms which is based on repulsion rather than attraction between the particles [3]. We will explain how these lattice-induced repulsively bound atom pairs come about and discuss their interesting properties. \newline [1] G. Thalhammer et al., Phys. Rev. Lett. 96, 050402 (2006). \newline [2] K. Winkler, cond-mat/0611222 \newline [3] K. Winkler et al., Nature 441, 853, (2006). \newline [Preview Abstract] |
Thursday, June 7, 2007 9:48AM - 10:24AM |
G1.00004: Evidence for superfluidity of ultracold fermions in an optical lattice Invited Speaker: Ultracold fermions in periodic potentials hold promise for studies of quantum order in crystalline materials, since the observables and the parameter regime accessed differ greatly from traditional condensed-matter systems. Condensation of fermion pairs is an example of macroscopic phase ordering, and is a first step towards the realization of more exotic orderings. Starting with a pure superfluid of $^{6}$Li pairs in the BEC-BCS crossover, we adiabatically ramp up an optical lattice potential and allow the system to equilibrate. Upon release, the atom cloud expands and self-interferes, revealing the phase-relation across the different lattice sites. The appearance of sharp momentum peaks corresponding to momenta 2$\hbar k$ carried by $^{6}$Li pairs of mass 2$m$ implies long-range phase coherence in the system. Such observations have traditionally been taken as an experimental indicator of superfluidity in an optical lattice, where the transport of atoms occurs by quantum mechanical tunneling and not by simple propagation. The effect of deep lattice depths and the role of interactions on the phase ordering and detection across the entire crossover are also explored. \newline \newline [1] J. K. Chin, D. E. Miller, Y. Liu, C. Stan, W. Setiawan, C. Sanner, K. Xu, W. Ketterle, Nature \textbf{443}, 961, (2006). [Preview Abstract] |
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