Bulletin of the American Physical Society
2006 37th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 16–20, 2006; Knoxville, TN
Session V3: Photoassociation, Efimov, and Feshbach Physics |
Hide Abstracts |
Chair: Brett Esry, Kansas State University Room: Knoxville Convention Center 301D |
Friday, May 19, 2006 1:30PM - 1:42PM |
V3.00001: Photoassociation Spectroscopy of Ultracold Atoms and the Study of ``Physicist's Molecules'' Eite Tiesinga, Kevin Jones, Paul Lett, Paul Julienne Photoassociation is the process where two colliding atoms absorb a photon to form an excited molecule. The development of laser cooling techniques for producing gasses at ultracold ($<$ 1 mK) temperatures has allowed photoassociation spectroscopy to be performed with very high spectral resolution. In particular, it has allowed the probing of ``purely long range" molecular states and the investigation of such ``physicist's molecules," - molecules whose properties can be derived with high precision from the properties of their constituent atoms. This presentation describes what is special about photoassociation spectroscopy at ultracold temperatures, how it is performed, and how it is used to investigate cold atomic collisions and extract atomic and molecular properties. We discuss the extraction of scattering lengths, their control via optical Feshbach resonances, precision determinations of atomic lifetimes, rate limits in a Bose-Einstein condensate, and briefly, production of cold molecules. Discussions are illustrated with examples on alkali-metal atoms as well as other species. This work has recently been accepted by the Review of Modern Physics. [Preview Abstract] |
Friday, May 19, 2006 1:42PM - 1:54PM |
V3.00002: Evidence for Efimov quantum states in an ultracold gas of cesium atoms B. Engeser, T. Kraemer, M. Mark, P. Waldburger, J.G. Danzl, C. Chin, A.D. Lange, K. Pilch, A. Jaakkola, H.-C. N\"agerl, R. Grimm A landmark theoretical advance in few-body quantum physics is Efimov's prediction of weakly bound three-body states occuring close to a two-body scattering resonance. Among the amazing properties predicted for Efimov states is the existence of weakly bound trimer states even when the interaction does not support a weakly bound dimer state. Since the Efimov problem originally occured 35 years ago in the context of nuclear matter, it has attracted great interest in many different areas of physics. In my talk I will report on the observation of an ``Efimov resonance'' as a clear manifestation of an Efimov state. The resonance arises in the zero collision energy limit from the coupling of three free atoms to an Efimov trimer and shows up as a giant three-body loss feature when the two-body interaction is magnetically tuned near a Feshbach resonance. Our results confirm central theoretical predictions of Efimov physics and represent a starting point to explore the universal properties of resonantly interacting few-body systems. [Preview Abstract] |
Friday, May 19, 2006 1:54PM - 2:06PM |
V3.00003: Ultracold Molecules Created near the continuum: Energy Structure and Efimov Physics Cheng Chin We present a two-channel model to describe weakly bound states of atoms near Feshbach resonances. This model provides a simple and accurate picture for the molecular energy structure and the bound state wave functions. We show that the results agree excellently with the measurements and the full multi-channel calculations. Several important issues will be addressed: first of all, we will discuss the strong and surprising dependence of Feshbach bound states on the background scattering properties. In the threshold regime, however, the bound state has a universal behavior and we will discuss the ``broadness'' of a resonance in the context of two-body physics and many-body physics. Finally, we will discuss trimer and tetramer energy structure in the vicinity of a Feshbach resonance and their connection to Efimov physics. [Preview Abstract] |
Friday, May 19, 2006 2:06PM - 2:18PM |
V3.00004: Atom-Dimer Coherence in Condensates of Strongly-Interacting Atoms Eric Braaten In a many-body system consisting of bosonic atoms with a large positive scattering length, atoms can flow coherently between coexisting Bose-Einstein condensates of atoms and weakly-bound dimers. A closed set of exact equations for the atom and dimer condensates can be rigorously derived using the one-particle-irreducible (1PI) effective action. Explicit approximate equations are obtained by truncating the 1PI effective action after the 2-body terms. Previous attempts to derive equations for atom-dimer coherence are critically examined. [Preview Abstract] |
Friday, May 19, 2006 2:18PM - 2:30PM |
V3.00005: Simple Analytic Theory of Cold Atom Feshbach Resonance Scattering Paul Julienne, Bo Gao Simple analytic theory, in excellent agreement with full quantum scattering calculations, is possible for the near-threshold resonant scattering 2-body T-matrix for magnetically tunable Feshbach resonances in ultracold atomic collisions. The theory is based on the analytic properties of the exact solutions to the Schrodinger equation for the van der Waals potential, and is characterized by 5 parameters: the scattering length, van der Waals coefficient, and reduced mass of the background entrance channel, the coupling width of the resonance, and the difference in magnetic moments between the separated atoms and the resonance level. The resonance scattering phase shift is completely characterized by two functions: an energy-dependent width and an energy-dependent shift, both of which are found from analytic functions determined by the background van der Waals potential. The excellent quality of the theory is illustrated by calculations of above-threshold scattering for the fermionic isotopes K-40, and Li-6 and for bosonic Rb- 85. [Preview Abstract] |
Friday, May 19, 2006 2:30PM - 2:42PM |
V3.00006: Formation and properties of cold quasi-one-dimensional molecules with Feshbach resonance interaction Vladimir Yurovsky, Abraham Ben-Reuven, Maxim Olshanii Bound states of cold atoms with two-channel two-body interactions in harmonic waveguides are analyzed. The two-atom problem can be approximated by a one-dimensional model at low energies and small values of the non-resonant scattering length [1,2]. In the case of a strong resonance, two-atom bound states contain mostly the contributions of the open channel. The closed channel contribution becomes dominant in weak resonances, such as the 543 G resonance in $^{6}$Li. The results are applicable both to bosonic and fermionic atoms. The formation of molecules by three-body association of indistinguishable bosonic atoms becomes allowed thanks to the non-integrability of the resonant one-dimensional three-body problem. This problem is analyzed by a numerical solution of the Faddeev-Lovelace equations [3]. A large value of the association rate coefficient of more then $10^{-4} \mathrm{cm}^2/\mathrm{s}$ is predicted in the vicinity of the weak Feshbach resonance in Na. The rate vanishes at large detunings, since the integrability is restored, and both at zero and at high collision energies. 1. V. A. Yurovsky, Phys. Rev. A {\bf 71}, 012709 (2005). 2. V. A. Yurovsky, physics/0601073. 3. V. A. Yurovsky, A. Ben-Reuven, and M. Olshanii, physics/0512033. [Preview Abstract] |
Friday, May 19, 2006 2:42PM - 2:54PM |
V3.00007: Optimal molecule production from Bose condensed atoms using non-linear magnetic field sweeps through a Feshbach resonance Jaeyoon Jeong, Christopher P. Search In most experiments involving conversion of ultracold atomic gases into molecules via a Feshbach resonance, a magnetic field, $B(t) $, is linearly swept across the resonance. In this case, Landau- Zener (LZ) theory predicts a high conversion efficiency if $\delta_{LZ}=\Omega_R^2/4|\Delta\mu\partial B/\partial t|>1$, where $\Delta\mu$ is the difference between the atomic and molecular magnetic moments and $\Omega_R$ is the coupling between the atoms and molecules. $\delta_{LZ}>1$ corresponds to adiabatic evolution for which the fraction of atoms converted into molecules is independent of the functional form of the sweep. For very fast linear sweeps such that $\delta_{LZ}\ll 1$, LZ theory predicts that almost no atoms are converted to molecules. Here we employ a genetic algorithm to determine the time dependence of the magnetic field that produces the maximum number of molecules when the duration of the sweep, $T$, is small enough for the evolution to be non-adiabatic, $\Omega_R^2< 4|\Delta\mu(B_{initial}-B_{final})|/T$. The optimal sweep through resonance shows that more than $95\%$ of the atoms can be converted into molecules for sweep times as short as $4\pi/\Omega_R$ while the linear sweep results in a conversion of $<10\%$. The qualitative form of the non-linear optimal sweep is independent of the strength of the two-body interactions and the width of the resonance. [Preview Abstract] |
Friday, May 19, 2006 2:54PM - 3:06PM |
V3.00008: Feshbach molecules and repulsively bound atom pairs in optical lattices Gregor Thalhammer, Klaus Winkler, Florian Lang, Rudolf Grimm, Johannes Hecker Denschlag Three dimensional optical lattices represent an interesting environment for fundamental research with ultracold atoms. We have prepared atomic Fock states in an optical lattice where individual sites are either empty or filled with two $^{87}$Rb atoms in the vibrational ground state of the lattice. With the help of a Feshbach resonance we are able to reversibly convert the pairs of atoms into Feshbach molecules with almost unit efficiency. We observe long molecular lifetimes because the lattice shields the trapped molecules from collisions and thus overcomes the problem of inelastic decay by vibrational quenching. Aside from the conversion into molecules, the atomic pairs themselves are very interesting to study because they exhibit counterintuitive and paradoxical behavior. Even though the two atoms in a lattice site effectively repel each other and each individual atom can quickly hop between lattice sites, pairs of atoms do not separate but form a metastable bound state. This can be explained by a strong restriction in phase space due to the lattice which forbids shedding of the repulsive potential energy of the pair. We have investigated the properties and stability of these strange two-body bound states. [Preview Abstract] |
Friday, May 19, 2006 3:06PM - 3:18PM |
V3.00009: Feshbach molecules from an atomic Mott insulator Thomas Volz, Niels Syassen, Dominik Bauer, Eberhard Hansis, Stephan Duerr, Gerhard Rempe Feshbach molecules from bosonic atomic species have proven to be very unstable with respect to inelastic collisions [1]. As a result, the typical lifetime observed for a cloud of ultracold $^{87}$Rb$_2$ molecules stored in an optical dipole trap is limited to a few ms.\\ Here, we report on the observation of long-lived Feshbach molecules in an optical lattice. A BEC of $^{87}$Rb atoms is loaded into the lowest Bloch band of a 3D optical lattice operated at a wavelength of $830~$nm. By ramping up the lattice depth, the atomic gas enters the Mott insulator regime. A magnetic-field ramp through the Feshbach resonance at $1007~$G creates molecules [2]. Lattice sites initially occupied with more than 2 atoms experience fast inelastic collisional losses. The observed lifetime of the remaining molecules is $\sim 100~$ms, which is much longer than for a pure molecular sample in an optical dipole trap. Similar results have recently been reported in Ref.[3]. The increased lifetime is an important step on the route to a BEC of molecules in the vibrational ground state [4].\\ \\ $[1]$ T. Mukaiyama et al., Phys. Rev. Lett. 92, 180402 (2004) \\ $[2]$ S. D\"urr et al., Phys. Rev. Lett. 92, 020406 (2004) \\ $[3]$ G. Thalhammer et al., cond-mat/0510755 \\ $[4]$ D. Jaksch et al., Phys. Rev. Lett. 89, 040402 (2002)\\ [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700