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 C3: Ultracold Atoms I |
Hide Abstracts |
Chair: Gil Summy, Oklahoma State University Room: Knoxville Convention Center 301D |
Wednesday, May 17, 2006 10:30AM - 10:42AM |
C3.00001: Determining $s$-wave Scattering Length Ratios from Binary Condensate Dynamics K. M. Mertes, J. W. Merrill, D. S. Hall, R. Carretero-Gonzalez, P. G. Kevrekidis, D. J. Frantzeskakis, H. E. Nistazakis We characterize experimentally and computationally the component separation dynamics of a binary Bose-Einstein condensate (BEC) created suddenly by a two-photon transition from a single BEC. In addition to inelastic losses, the condensate dynamics depend crucially on the three $s$-wave scattering lengths (inter- and intraspecies), which are nearly identical in ${}^{87}$Rb. The experimentally observed density distributions exhibit striking transient ring patterns that closely correspond to the results of numerical simulations. The simulations exhibit a sensitive dependence on the ratios of the scattering lengths; we can therefore extract these ratios by comparing simulation to experiment. [Preview Abstract] |
Wednesday, May 17, 2006 10:42AM - 10:54AM |
C3.00002: Spin noise spectroscopy to probe quantum states of ultracold fermionic atom gases Bogdan Mihaila, Scott Crooker, Krastan Blagoev, Dwight Rickel, Darryl Smith, Peter Littlewood Ultracold alkali atoms provide experimentally accessible model systems for probing quantum states that manifest themselves at the macroscopic scale. Recent experimental realizations of superfluidity in dilute gases of ultracold fermionic atoms offer exciting opportunities to directly test theoretical models of related many-body fermion systems that are inaccessible to experimental manipulation. However, the microscopic interactions between fermions are potentially quite complex, and experiments in ultracold gases to date cannot clearly distinguish between the qualitatively different microscopic models that have been proposed. Here, we theoretically demonstrate that optical measurements of electron spin noise can probe the entangled quantum states of ultracold fermionic atomic gases and unambiguously reveal the detailed nature of the interatomic interactions. We show that different models predict different sets of resonances in the noise spectrum, and once the correct effective interatomic interaction model is identified, the line-shapes of the spin noise can be used to constrain this model. Experimental measurements of spin noise in classical alkali vapors are used to estimate the expected signal magnitudes for spin noise measurements in ultracold atom systems and to show that these measurements are feasible. [Preview Abstract] |
Wednesday, May 17, 2006 10:54AM - 11:06AM |
C3.00003: High-temperature superfluidity in an ultracold Fermi gas Andre Schirotzek, Martin Zwierlein, Christian Schunck, Wolfgang Ketterle Quantum degenerate atomic Fermi gases provide a remarkable opportunity to study strongly interacting Fermions. In contrast to other Fermi systems, such as superconductors, neutron stars or the quark-gluon plasma of the early Universe, these gases have low densities and their interactions can be precisely controlled over an enormous range. Our recent observation of vortex lattices in a rotating Fermi gas provides definitive evidence for superfluidity in these systems. Scaled to the density of electrons in a solid, this new form of superfluidity would occur already above room temperature. [Preview Abstract] |
Wednesday, May 17, 2006 11:06AM - 11:18AM |
C3.00004: Suppression of inelastic collisions in atom waveguides Vladimir Yurovsky, Yehuda Band Collisional deactivation is analyzed using a multichannel zero-range potential method. The deactivation products are associated to a set of open channels, while introduction of a closed channel leads to a Feshbach resonance, allowing control of elastic scattering. In the case of free space the deactivation rate coefficient has a finite zero-energy limit. It increases with the elastic scattering length, demonstrating also the effect of interference of open and closed channel deactivation. A tight confinement in atomic waveguides leads to a drastic change of the deactivation rate behavior. At large elastic scattering length, the rate coefficient decreases to zero at low collision energies. The present two-body analysis is in agreement with the many-body consideration of indistinguishable particles [1], being applicable to non-identical particles as well. The general behavior of two-body correlations [1] can be reproduced in the present two-body picture. 1. D. M. Gangardt and G. V. Shlyapnikov, Phys. Rev. Lett. {\bf 90}, 010401 (2003). [Preview Abstract] |
Wednesday, May 17, 2006 11:18AM - 11:30AM |
C3.00005: Optical Manipulation of BEC's using the Talbot Effect Mark Edwards Gaseous Bose-Einstein condensates (BEC) can be placed in novel momentum states by applying two high-intensity, short-pulse counterpropagating laser pulses separated by a variable time delay$^{1}$. The long-time momentum state of the condensate, which consists of a superposition of integral multiples of $2 \hbar k$ (twice the laser photon momentum,) depends on the delay between the pulses and their relative intensites. We have extended the theory to apply to a sequence of pulses and delays. The effect of a laser pulse on the condensate momentum state is that the amplitude to jump from momentum eigenstate $2m\hbar k$ to $2n\hbar k$ is $i^{n-m}J_{n-m}\left(\alpha\right) $ where $\alpha$ is proportional to the laser intensities. Between the pulses, each momentum component evolves as a free particle with the appropriate momentum. Using these two elements, any sequence of pulses and delays can be analyzed. We present this theory in detail and analyze a sequence of pulses and delays designed to place the condensate atoms in a state with only two (equal and opposite) momentum components.\\ $^{1}$ L. Deng et al.,{\em Temporal Matter-Wave-Dispersion Talbot Effect} Phys.\ Rev.\ Lett.\ {\bf 83} 5407 (1999) [Preview Abstract] |
Wednesday, May 17, 2006 11:30AM - 11:42AM |
C3.00006: $^{7}$Li BEC in a millimeter-scale Ioffe-Pritchard trap Mingchang Liu, Ruquan Wang, Francesco Minardi, Mark Kasevich A millimeter-scale Ioffe-Pritchard type magnetic trap with excellent optical access has been used to demonstrate Bose-Einstein condensation in$^{ 7}$Li. The trap utilizes a novel combination of free space and substrate patterned current carrying elements to produce the required fields. Substrate electrodes are fabricated with using the direct-bond copper (DBC) process on a ceramic substrate. DBC fabrication enables excellent thermal dissipation together with high current capacity vias and surface conductors. With 100A trapping current, which dissipates less than 10W the trap provides 400G/Cm magnetic gradient in the radial direction, 50Hz trapping frequency in axial direction and 80G trap depth for $^{7}$Li. With conventional water cooling, lifetime for the trap is over 1 minute and BEC regime is reached after 35s forced evaporation. The demonstrated performance for $^{7}$Li is expected to scale well to other alkalis and this compact configuration may serve as an excellent platform for mobile ultra-cold atom sensors. [Preview Abstract] |
Wednesday, May 17, 2006 11:42AM - 11:54AM |
C3.00007: Spectral and time-dependent multiple light scattering in ultracold atomic $^{85}$Rb S. Balik, R.G. Olave, C.I. Sukenik, M.D. Havey, V.M. Datsyuk, D.V. Kupriyanov, I.M. Sokolov Multiple light scattering can generate distributed coherences in an optically dense ultracold atomic gas. An intriguing possibility is that at high enough atom densities, the coherences collapse into spatially localized subradiant excitations. Theories of strong light localization in condensed samples show that diffusive transport is strongly suppressed; in atomic samples, this would be reflected in the time dependence of emergence of light from the ultracold gas samples. At lower densities, light transport is approximately diffusive, and can be effectively modelled by, for example, Monte Carlo simulations of the multiple scattering process. We present in this paper experimental data on the spectral and time dependence of light emerging from a sample of ultracold and dense (peak optical depth b = 8(1)) $^{85}$Rb atoms. For off-resonance excitation, the time-dependence measurements show transient beats upon turn-on of the pulsed excitation. Surprisingly, the transient decay of the intensity shows a nearly constant decay rate at longer times, independent of the detuning of the excitation pulse frequency from resonance. Monte-Carlo simulations of the process successfully describe the full temporal behavior of the fluorescence intensity, and support physical interpretations of the observations. [Preview Abstract] |
Wednesday, May 17, 2006 11:54AM - 12:06PM |
C3.00008: Measurements on RF-dressed Bose Einstein Condensates Matthew R. White, Hong Gao, Matthew Pasienski, Brian DeMarco The formation of dressed states from the Zeeman sublevels of magnetically trapped atoms in an applied RF field is relevant to processes such as evaporative cooling and atom lasers. In this work, we investigate a dressed state condensate of ${}^{87}$Rb atoms in the $F=1$ state. The spin state composition of RF-dressed, magnetically trapped atoms is measured and the transfer of dressed atoms into adiabatic potentials is explored. Finally, we discuss potential applications to trapping atoms in novel geometries. [Preview Abstract] |
Wednesday, May 17, 2006 12:06PM - 12:18PM |
C3.00009: Metastable Bose-Einstein Condensates in a Linear Potential Devang Naik, Mishkat Bhattacharya, Sergio Muniz, Chandra Raman We have created a trapped BEC whose spin orientation is metastable in an external, inhomogeneous magnetic field. This trapping field can in principle be used to coherently control the coupling between spin and spatial wavefunctions. Although subject to Majorana losses, we've noticed lifetimes of a few hundred milliseconds. Atoms held in the trap for this amount of time have frequently displayed ring-shaped time-of-flight distributions, whose origins might be due to quantized vortices or a feature of the Majorana loss dynamics in the quantum regime. [Preview Abstract] |
Wednesday, May 17, 2006 12:18PM - 12:30PM |
C3.00010: Measurement of the temperature dependence of the Casimir-Polder force through collective excitations of a Bose-Einstein condensate John Obrecht, Robert Wild, David Harber, Colleen Gillespie, Eric Cornell A Rb-87 Bose-Einstein condensate is positioned microns from a dielectric surface and resonantly excited into a mechanical dipole oscillation. Changes in the collective oscillation frequency of the magnetically trapped condensate result from spatial variations in the atom-surface force [1,2]. Recent theoretical work has characterized the temperature dependence of non-equilibrium Casimir-Polder forces [3] in which the temperature of the dielectric surface is different from the temperature of free-space. In our experiment a dielectric surface is heated to 600K while the surrounding environment is kept near room temperature (310K). The magnitude of the Casimir-Polder force is measured in both this non-equilibrium configuration and also in a room temperature equilibrium configuration. Both measurements agree with theoretical predictions, marking the first demonstration of the temperature dependence of the Casimir-Polder force. [1] M. Antezza, L.~P. Pitaevskii and S. Stringari, Phys. Rev. A {\bf 70}, 053619 (2004). [2] D.~M. Harber, J.~M. Obrecht, J.~M. McGuirk and E.~A. Cornell, Phys. Rev. A {\bf 72}, 033610 (2005). [3] M. Antezza, L.~P. Pitaevskii and S. Stringari, Phys. Rev. Lett. {\bf 95}, 113202 (2005). [Preview Abstract] |
Wednesday, May 17, 2006 12:30PM - 12:42PM |
C3.00011: Direct observation of mean-field induced phase collapse and retrieval in soft bosonic lattices Wei Li, Ari Tuchman, Hui-chun Chien, Mark Kasevich We study the response of BEC+optical lattice system to sudden frustration of Josephson tunneling between adjacent lattice sites in the large filling factor (soft) regime[1]. We introduce a new experimental method which effectively discriminates between~homogeneous (on-site)~phase diffusion[2] and inhomogeneous (site-to-site) dephasing mechanisms. With this method, we observe quantitative agreement between the predicted and measured phase diffusion times. In particular, we demonstrate that the phase diffusion time can be increased by reducing the number fluctuations associated with the initial lattice states. This work extends the work of Greiner, et al.[3] to the large filling factor regime. Finally, we describe and demonstrate a technique for retrieval of long range phase coherence from this system. Surprisingly, coherence can be suddenly regained by abruptly allowing Josephson tunneling. We discuss the implications of these observations for envisioned superfluid de Broglie wave interferometers and in the study of non-adiabatic effects in superfluid/Mott-insulating systems. \newline [1] Orzel, C., Tuchman, A. K., Fenselau, M. L., Yasuda, M. {\&} Kasevich, M. A. \textit{Science} \textbf{291}, 2386-2389 (2001).~ [2] A. Imamoglu, M. Lewenstein {\&} L. You. Phys. Rev. Lett. \textbf{78}, 2511(1997). [3]~ M. Greiner, O. Mandel, T. Esslinger, T. W. H\"{a}nsch {\&} I. Bloch. Nature \textbf{415}, 39 (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