Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session B6: Few-body Aspects of Cold Atomic Gases |
Hide Abstracts |
Sponsoring Units: DAMOP Chair: Robin Cote, University of Connecticut Room: Ballroom C2 |
Monday, March 21, 2011 11:15AM - 11:51AM |
B6.00001: Interacting and Rotating Gases of a Few Trapped Atoms Invited Speaker: I will discuss attempts to generate motionally entangled states in small clusters of repulsively interacting Bosonic atoms at nonzero angular momentum in two-dimensional harmonic traps.\footnote{Gemelke, N., Sarajlic, E., Chu, S., arXiv:1007.2677} By constructing an ``array of rotating buckets'' from an optical lattice of spinning and precisely controlled on-site potentials, small clusters of interacting atoms can be adiabatically transferred from uncorrelated states at zero angular momentum through a tabulated sequence of ground state level crossings with increasing atomic correlation and total angular momentum. Results will be shown probing these states with both time-of- flight techniques and by directly interrogating atomic correlation via photo-association to excited molecules. Comparison will be made to numeric models with no free parameters. I will discuss extension of these results to future experiments using Feshbach-resonant interactions, and the use of dynamically modulated lattice potentials to generate effective gauge fields. [Preview Abstract] |
Monday, March 21, 2011 11:51AM - 12:27PM |
B6.00002: Deterministic preparation and control of a tunable few-fermion system Invited Speaker: Systems consisting of only few interacting fermions play a fundamental role in nature with atoms and atomic nuclei being the most prominent examples. In our experiments with ultracold atoms we have recently been able to prepare and control few-atom quantum states consisting of 1-10 fermions. We prepare such a system using ultracold $^6$Lithium atoms in an optical dipole trap in which the interparticle interaction can be tuned over a wide range using a Feshbach resonance. By spilling all atoms occupying higher energy quantum states we can deterministically prepare samples from 1-10 particles in the ground state with fidelities exceeding 90\%. In my talk I will present our first experiments controlling the interaction between particles in the ground state of the trap. [Preview Abstract] |
Monday, March 21, 2011 12:27PM - 1:03PM |
B6.00003: Four-body Efimov effect Invited Speaker: The few-body problem with resonant two-body $s$-wave interaction (that is with an infinite scattering length) can now be studied experimentally with ultracold atomic gases. In particular, the three-body Efimov phenomenon (Efimov, 1971), consisting in the existence of an infinite number of trimer states with an asymptotically geometric spectrum in the vicinity of a zero energy accumulation point, has now obtained experimental evidence. On the contrary, the four-body Efimov effect has remained elusive, both theoretically and experimentally. Strictly speaking, for same spin state bosons, as pointed out by Amado and Greenwood (1973), it is {\sl a priori} excluded by the existence of the three-body Efimov effect: A tetramer state with an energy arbitrarily close to zero has eventually an energy larger than an Efimov trimer state and may decay into this trimer plus a free atom. We have found a system where a four-body Efimov effect takes place: It is made of three same spin state fermions of mass $M$ interacting only with a lighter particle of mass $m$. The mass ratio $\alpha=M/m$ is used as a control knob: This system experiences a three-body Efimov effect if and only if $\alpha>\alpha_c(2;1)\simeq 13.607$ (Efimov, 1973; Petrov, 2003). Using a combination of symmetry arguments and a numerical solution of an integral equation,we show that Efimov tetramers exist over the interval of mass ratio $\alpha_c(3;1) < \alpha < \alpha_c(2;1)$, with $\alpha_c(3;1)\simeq 13.384$. The four-body Efimov exponent $|s|$ is also calculated as a function of $\alpha$ over that interval, and the experimental feasibility is discussed. [Preview Abstract] |
Monday, March 21, 2011 1:03PM - 1:39PM |
B6.00004: Interferometry with ultra-cold few-atom states Invited Speaker: I will explain some of our recent modeling of experiments that loaded an atomic Bose-Einstein condensate into a three-dimensional optical lattice. In an optical lattice, a periodic trap for atoms, the condensate can be divided into millions of independent atomic coherent states. These states are superpositions of different atom number and the analogue of coherent states of light or photons. As in the case of coherent laser light these atomic states can be made to interfere. In fact, the time-evolution of the states leads to collapse and revivals in interference patterns observed in the atomic momentum distribution. I show that long-period revivals are associated to effective three-body interactions that are due to virtual excitations to higher vibrational states within a site of an optical lattice. This work has been published as P. R. Johnson, E. Tiesinga, J. V. Porto, and C. J. Williams, New Journal of Physics {\bf 11}, 093022 (2009). [Preview Abstract] |
Monday, March 21, 2011 1:39PM - 2:15PM |
B6.00005: Virial Expansion for a Strongly Correlated Fermi Gas Invited Speaker: Few-body physics can give considerable insight into the challenging many-body problem. A concrete example is the exact Tan relations [1] linking the ``hard'' (few-body) physics at short distance, large-momentum and high frequency to the ``soft'' physics of the equation of state via a contact parameter. This has been demonstrated clearly using the operator product expansion (OPE) method [2] which separates in a natural way few-body from many-body physics. In this talk, we present another example: the quantum virial expansion that bridges few-body and many-body physics. At large temperatures, the properties of a strongly correlated Fermi gas, either static or dynamic, can be expanded in terms of virial coefficients or expansion functions, calculable from the few-fermion solutions [3]. For the equation of state in the resonant unitarity limit [3], we obtain for the first time an accurate third order virial coefficient. This has been experimentally verified in a measurement at ENS (Paris) [4]. For the single-particle spectral function [5], we demonstrate that an expansion up to second order is able to explain the main features of momentum-resolved RF spectroscopy in a resonantly interacting Fermi gas, as recently reported by JILA [6]. We also obtain a virial expansion of the dynamic structure function, as measured at Swinburne University (Melbourne), and check that the second order expansion functions give the correct OPE coefficients in the limit of large momentum and frequency. The important feature of this expansion is the existence of a small parameter, the fugacity, even for strong interactions. In the future, we anticipate that higher-order virial expansions of dynamic properties such as the single-particle spectral function may provide useful insights into clarifying the debate on the pseudo-gap issue in resonantly interacting Fermi gases. \\[4pt] [1] S. Tan, \textit{Ann. Phys}. \textbf{323}, 2952 (2008); \textbf{323}, 2971 (2008).\\[0pt] [2] E. Braaten, and L. Platter, \textit{Phys. Rev. Lett}. \textbf{100}, 205301 (2008).\\[0pt] [3] X.-J. Liu, H. Hu, and P. D. Drummond, \textit{Phys. Rev. Lett}. \textbf{102}, 160401 (2009).\\[0pt] [4] S. Nascimb\`{e}ne et al. \textit{Nature} \textbf{463}, 1067 (2010).\\[0pt] [5] H. Hu, X.-J. Liu, and P. D. Drummond, \textit{Phys. Rev. Lett}. \textbf{104}, 240407 (2010).\\[0pt] [6] J. T. Stewart, J. P. Gaebler, and D. S. Jin, \textit{Nature} \textbf{454}, 744 (2008). [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