Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session J4: Efimov States and other Many-Body Interactions |
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Chair: Cheng Chin, University of Chicago Room: Clark Hall 108 |
Thursday, May 21, 2009 8:00AM - 8:12AM |
J4.00001: The Efimov Effect and Color Superconductivity in a Three-State Fermi Gas J.R. Williams, E.L. Hazlett, J.H. Huckans, R.W. Stites, Y. Zhang, K.M. O'Hara We have created a quantum degenerate $^6$Li gas with equal populations in the three lowest energy hyperfine states. This three-state Fermi gas is stable against two-body inelastic collisions but decays by three-body recombination. We measure the rate of three-body recombination which can be used as a signature of the Efimov effect and which determines whether conditions are favorable for BCS pairing. The three pairwise $s$-wave scattering lengths exhibit overlapping Feshbach resonances at 690, 810 and 834 Gauss. As we vary the field between 0 and 834 Gauss, we find that the three-body recombination rate constant varies by over four orders of magnitude. High stability is achieved near 0 and 570 Gauss. We observe narrow resonant loss features near 130 and 500 Gauss. Recent calculations indicate that these resonant features arise from Efimov trimer states near threshold [1,2]. We also report on the rate of three-body recombination between 834 and 2000 Gauss. Our determination of the three-body parameters in this regime will guide future experiments aimed at achieving color superconductivity in this system.\\[4pt] [1] E. Braaten, H.-W. Hammer, D. Kang, \& L. Platter, arXiv:0806.0587.\\[0pt] [2] P. Naidon \& M. Ueda, arXiv:0811.4086. [Preview Abstract] |
Thursday, May 21, 2009 8:12AM - 8:24AM |
J4.00002: Extracting Efimov physics from three-body recombination at finite energies Yujun Wang, J.P. D'Incao, B.D. Esry We have identified energy-dependent features in the three-body recombination rate that trace their origin to Efimov physics. These features manifest themselves as log-periodic sinusoidal modulations of the rates as a function of energy. This log-periodic behavior provides the link to Efimov physics. Using a model two-body interaction, we calculate the recombination rate numerically for identical bosons and for the Cs-Li mixture. We show, however, that the energy modulations are more clear in Cs+Cs+Li recombination. We will also discuss the issues important for observing these features experimentally. [Preview Abstract] |
Thursday, May 21, 2009 8:24AM - 8:36AM |
J4.00003: A step beyond the Efimov scenario: evidence of a universal four-body state Francesca Ferlaino, Steven Knoop, Martin Berninger, Walter Harm, Hanns-Christoph Naegerl, Rudolf Grimm Ultracold cesium atoms and Feshbach molecules provide unique model systems to explore universal few-body phenomena. In previous experiments, we have investigated atomic three-body recombination and atom-dimer relaxtion in ultracold atomic and molecular samples at large scattering lengths and obtained clear evidence for Efimov three-body states. Here, we report on a step beyond the Efimov scenario by investigating a four-body phenomenon that was recently predicted by von Stecher et al. (arXiv:0810.3876). Our recombination measurements in an atomic sample at negative scattering lengths show a resonant enhancement of losses and provide strong evidence for the existence of the predicted four-body bound states. [Preview Abstract] |
Thursday, May 21, 2009 8:36AM - 8:48AM |
J4.00004: Universal four-body resonances in ultracold atomic and molecular gases Jose P. D'Incao, Javier von Stecher, Chris H. Greene We study the manifestations of universal four-body physics in ultracold, strongly interacting, atomic and molecular gases. We find that ultracold scattering observables such as four-body recombination and dimer-dimer relaxation, display resonant structure caused by the emergence of universal four-boson states. Such resonant effects enable the control of few-body interactions and potentially enrich the range of experimentally accessible phenomena. We also demonstrate the close relationship between universal four-body physics with Efimov physics. Our analysis shows that $B_{2}+B_{2}\rightarrow B_{3}+B$ rearrangement reactions offers a path for an efficient trimer formation, building the bridge between three- and four-body universal physics. Our analysis of the temperature dependence of this reaction provides an interpretation of the available experimental data and sheds light on the possible experimental realization of rearrangement processes in ultracold gases. This work was supported by the National Science Foundation. [Preview Abstract] |
Thursday, May 21, 2009 8:48AM - 9:00AM |
J4.00005: Investigating Many-body Physics with Ultracold Molecules in Optical Lattices Michael Wall, Lincoln Carr Ultracold polar molecules, with their large internal Hilbert space and significant electric dipole moments, offer exciting prospects for the production of novel many-body effects when placed in an optical lattice. In this talk we present a new lattice Hamiltonian, the \emph{Molecular Hubbard Hamiltonian} (MHH), which is a natural Hamiltonian for the study of many-body effects using experimental setups that can be performed in the immediate future with established techniques in ultracold molecular quantum gases. We will explain the Hamiltonian, its physical motivation, and the significant differences with typical Hubbard-like models realized with ultracold atomic gases. We will then show results from entangled quantum dynamics simulations demonstrating that the Hamiltonian exhibits emergent time scales over which spatial entanglement grows, crystalline order appears, and oscillations between rotational states self-damp into an asymptotic superposition. [Preview Abstract] |
Thursday, May 21, 2009 9:00AM - 9:12AM |
J4.00006: Strongly Correlated Few-Boson Dynamics in Waveguides Peter Schmelcher, Sascha Zoellner, Vladimir Melezhik The transition of a one-dimensional trapped few-boson system from weak to strong correlations including the fermionized limit is investigated. Our numerically exact analysis, based on the Multi-Configuration Time-Dependent Hartree method, explores the interplay between different shapes of external trapping and inter-particle forces by analyzing the one-particle density and density matrix as well as the two-particle correlation function. The main focus is the exploration of few-boson tunneling in multi-well systems. As we pass from weak interactions to the fermionization limit, the Rabi oscillations first give way to highly delayed correlated pair tunneling, whereas for very strong correlations multi-band Rabi oscillations include fragmented pair tunneling. Finally we briefly discuss the recently found effect of confinement induced transparency of ultracold scattering in a strongly confining waveguide. The underlying mechanism is the interference of the gerade and ungerade scattering contributions leading to transparency in the cold collisions This is the dual effect to the well-known confinement-induced resonance. [Preview Abstract] |
Thursday, May 21, 2009 9:12AM - 9:24AM |
J4.00007: Counterflow and paired superfluidity in one-dimensional Bose mixtures Anzi Hu, Ludwig Mathey, Ippei Danshita, Carl Williams, Charles Clark We study the quantum phases of 1D Bose mixtures using Luttinger liquid theory and the numerical method,TEBD. We consider a binary mixture with both repulsive and attractive inter-species interaction. We first present the phase diagram for a homogeneous system. In particular, we study the paired superfluid(PSF) and counterflow superfluid(CFSF) phases at different filling and hopping energies,as well as parameter regions where PSF/CFSF coexist with charge density wave (CDW) order.Then we address the question of how these phases can be created and detected in the presence of a trap. We present measurable quantities, such as time-of-flight images and noise correlations. We also suggest applying a Feshbach ramp and $\pi$/2 pulse followed by Bragg spectroscopy as possible ways of detection. [Preview Abstract] |
Thursday, May 21, 2009 9:24AM - 9:36AM |
J4.00008: Observation of Spin-Polarons in a tunable Fermi liquid Andre Schirotzek, Cheng-Hsun Wu, Ariel Sommer, Martin Zwierlein We have observed Spin-Polarons, dressed spin down impurities in a spin up Fermi sea. rf spectroscopy can directly reveal the polaronic nature of the impurity particles and allows for an experimental measure of the quasiparticle residue Z and the chemical potential $\mu$ of this novel Fermi liquid. The polarons are found to be only weakly interacting with each other, and can thus be identified with the quasi-particles of Landau's Fermi liquid theory. At a critical interaction strength, the transition to two-particle molecular binding is observed, constituting a phase transition from a Fermi liquid to a Bose liquid. Furthermore, we will give an outlook on experiments determining the effective mass $m$* of the observed Spin-Polarons, another central quantity of Fermi liquid theory. [Preview Abstract] |
Thursday, May 21, 2009 9:36AM - 9:48AM |
J4.00009: Polarized Fermi Gases at Unitarity in Anisotropic traps Leslie Baksmaty, Han Pu, Hong Lu, Carlos Bolech We discuss recent apparently contradictory experimental results on trapped polarized resonantly interacting interacting fermions. Our analysis occurs in the context of a full 3D Bogoliubov deGennes analysis and we dwell on the possible roles of the confining geometry in producing density distortions away from the local density approximation with implications for the Superfluid-Normal transition (Clogston limit). [Preview Abstract] |
Thursday, May 21, 2009 9:48AM - 10:00AM |
J4.00010: Prospects for ultracold dipolar physics, microscopy, and QIP with dysprosium Benjamin Lev, Seo Ho Youn, Mingwu Lu, Ushnish Ray Highly magnetic atoms such as dysprosium offer the ability to create strongly correlated matter in both atomic physics and quantum optics settings. In addition, these atoms will form the key ingredient in novel devices possessing unsurpassed sensitivity and resolution for the microscopy of condensed matter materials. We discuss prospects for laser cooling and trapping dysprosium on chips and in optical lattices. Such progress will lead to three research projects: the investigation of quantum liquid crystal physics in fermionic dipolar lattices; the exploration of non-equilibrium quantum phase transitions in many body cavity QED; and the development of atom chip microscopy at the greater than $10^{-7}$ magnetic flux quantum level. [Preview Abstract] |
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