Bulletin of the American Physical Society
2012 Annual Fall Meeting of the APS Prairie Section
Volume 57, Number 14
Thursday–Saturday, November 8–10, 2012; Lawrence, Kansas
Session B2: Atomic, Molecular and Optical Physics |
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Chair: Hui Zhao, University of Kansas Room: Oread Hotel Griffith Room |
Friday, November 9, 2012 10:40AM - 11:15AM |
B2.00001: From cosmology to cold atoms: observation of Sakharov oscillations in quenched atomic superfluids Invited Speaker: Cheng Chin Sakharov oscillations, conventionally discussed in the context of early universe evolution and the anisotropy of cosmic microwave background radiation, is the manifestation of interfering acoustic waves synchronously generated in an ideal fluid. In atomic superfluids, the ease to induce acoustic excitations makes them a convenient test ground to simulate and study this intriguing phenomenon in the laboratory setting. In recent years, many ideas have been proposed to associate cosmological and gravitational phenomena to the non-equilibrium dynamics of quantum gases. Here we report the laboratory observation of Sakharov oscillations in a quenched atomic superfluid. We quench the sample by Feshbach tuning and monitor the subsequent density fluctuations at different time and length scales by in situ imaging. Sakharov oscillations are identified as the multi-peak structure in the atomic density power spectrum, resembling that of the cosmic microwave background radiation. We also observe Sakharov oscillations in the time domain, from which we extract the energy dispersion of the superfluid, and determine the sonic horizon of the excitations. Our work opens up new perspectives to investigate non-equilibrium dynamics of quantum fluids and its analogues in cosmology and astrophysics. [Preview Abstract] |
Friday, November 9, 2012 11:15AM - 11:27AM |
B2.00002: Resonant enhancement of single attosecond pulses by time-delayed control field Wei-Chun Chu, Chii-Dong Lin An attosecond coherent control scheme is theoretically investigated. An XUV single attosecond pulse propagates through a dense helium gas medium dressed by a time-delayed laser pulse. The laser pulse in the intensity range 10$^{12}$-10$^{13}$ W/cm$^2$ couples the $2s2p(^1P)$ and $2s^2(^1S)$ resonances while the weak XUV pulse excites the former from the ground state. By tuning the dressing field specifically, we demonstrate an enhancement of the XUV pulse at the resonance energy up to 50\% of the input intensity, which exemplifies the reshaping of a broadband attosecond pulse controlled by an ultrashort laser for the first time. [Preview Abstract] |
Friday, November 9, 2012 11:27AM - 11:39AM |
B2.00003: Equations of state of strongly interacting two-dimensional Bose gases Li-Chung Ha, Chen-Lung Hung, Ulrich Eismann, Shih-Kuang Tung, Cheng Chin We study strongly interacting two-dimensional Bose gases based on \textit{in situ} density profiles of the sample in the superfluid and critical fluctuation regimes. We achieve strong interaction between atoms by using a magnetically tuned Feshbach resonance and by confining the atoms into an optical lattice. In the superfluid phase, the measured compressibilities deviate from the mean-field prediction when the interaction is strong, and are in better agreement with the renormalization calculation. Near the critical point of the Berezinskii-Kosterlitz-Thouless transition, we find that the equations of state scale universally with respect to the interaction strength within the strength range we probe. We extract the critical chemical potentials, critical densities as well as the renormalized interaction strengths and compare the results to the mean-field and renormalization calculations. [Preview Abstract] |
Friday, November 9, 2012 11:39AM - 11:51AM |
B2.00004: Identification of collisional resonances and three-body universality based on an ultracold mixture of Li-6 and Cs-133 atoms Shih-Kuang Tung, Colin Parker, Jacob Johansen, Cheng Chin One unique feature about ultracold atom experiments is that we are able to control how atoms interact. When two atoms move towards each other, their scattering wavefunction can couple to a bound state near the scattering continuum, and the scattering amplitude can develop a resonant enhancement, which we called a Feshbach resonance. Here we report our observations on the Feshbach resonances in an ultracold mixture of fermionic Li-6 and bosonic Cs-133 atoms. Those resonances provides us essential information to control the interactions between the two atomic species, which opens up many exciting research fronts, especially to explore the three-body universality of the mixture. [Preview Abstract] |
Friday, November 9, 2012 11:51AM - 12:03PM |
B2.00005: Quantum Mechanics Without Planck's Constant John Ralston Planck's constant was introduced as a fundamental unit in the early history of quantum mechanics. We find a modern approach where Planck's constant is absent: It is unobservable except as a constant of human convention. Despite long reference to experiment, review shows that Planck's constant cannot be obtained from the data of Ryberg, Davisson and Germer, Compton, or that used by Planck himself. In the new approach Planck's constant is tied to macroscopic conventions of Newtonian origin, which are dispensable. The precision of other fundamental constants is substantially improved by eliminating Planck's constant. The electron mass is determined about 67 times more precisely, and the unit of electric charge determined 139 times more precisely. Improvement in the experimental value of the fine structure constant allows new types of experiment to be compared towards finding ``new physics.'' The long-standing goal of eliminating reliance on the artifact known as the International Prototype Kilogram can be accomplished to assist progress in fundamental physics. [Preview Abstract] |
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