Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session H7: Few-body Systems |
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Chair: Jason Nguyen, Rice University Room: 553AB |
Wednesday, May 25, 2016 10:30AM - 10:42AM |
H7.00001: Accessing the quantum Hall regime in cold atom traps using circularly polarized light Rachel Wooten, Bin Yan, Chris H. Greene There has been considerable interest in designing cold atom experiments to explore the quantum Hall effect with the extreme control allowed in such trapped atom systems. Many theoretical proposals and experimental attempts have been made in the effort to construct a cold atom fractional quantum Hall experiment, but so far, the fractional quantum Hall regime has proven difficult to achieve in experimental setups. One method for reaching the quantum Hall effect consists of rapidly rotating a cold atom system in a harmonic trap to near the centrifugal limit, where the system's Hamiltonian matches the two-dimensional magnetic field Hamiltonian. This condition could be reached in a few-body system through a scheme which increases the angular momentum of the particles in the trap through precision photon excitations. According to the hyperspherical framework from few-body theory, when particle interactions break the harmonic energy spectrum degeneracy, it becomes possible for circularly polarized light to excite the system selectively into the high angular momentum states required for the quantum Hall effect. We will discuss possible experimental systems where this technique could be applicable and challenges that these systems may face. [Preview Abstract] |
Wednesday, May 25, 2016 10:42AM - 10:54AM |
H7.00002: Exploration of scattering resonances in the presence of Rashba-Dresselhaus spin-orbit coupling Su-Ju Wang, Chris Greene Engineering dispersion relations of the center-of-mass motion of cold atoms using lasers allows quantum simulations and the study of some exotic physics. The recent experimental realizations of equal Rashba and Dresselhaus spin-orbit coupling (E-RDSOC) in both ultracold bosonic and fermionic atoms enable ultracold atomic systems to display SOC physics. Spin-orbit coupling often exhibits a double-minimum energy-momentum dispersion. The two-body scattering threshold in the E-RDSOC scheme is found to be determined by the ratio of the SOC strength and the Raman coupling strength. When the critical SOC strength is met, the energy dispersion changes from a single-minimum structure to a double-minimum structure. Possible scattering resonances associated with bound states in the closed channels are explored in the double-minimum region. [Preview Abstract] |
Wednesday, May 25, 2016 10:54AM - 11:06AM |
H7.00003: Ultracold two-body dynamics in optical lattices with topological singularities Davit Aghamalyan, Andrea Simoni, Jean-Michel Launay We study bound levels of two particles trapped in a 2D optical lattice. We use a short-range potential tuned to reproduce typical experimental conditions. Near-threshold bound states are computed using a spectral element discretization approach that guarantees exponential precision in the numerical results. High computational efficiency is attained due to the very sparse nature of the Hamiltonian in this representation. The calculated wavefunction is analyzed both in real and in momentum space. We perform calculations both for standard separable optical potentials and for lattice with topological singularities (Dirac cones) in the band structure. Extension to the calculation of scattering states will be addressed. [Preview Abstract] |
Wednesday, May 25, 2016 11:06AM - 11:18AM |
H7.00004: Three-body recombination near a narrow Feshbach resonance in $^6$Li Le Luo, Jiaming Li, Ji Liu, Leonardo de Melo, Bo Gao $^6$Li narrow Feshbach resonance near a magnetic field of 543.3 Gauss allows studies of strongly interacting fermions with a large effective range [1]. Above the resonance threshold, three-body recombination rate $L_{3}$ is dramatically enhanced by the formation of metastable dimers [2], which subsequently decay via atom-dimer relaxation that can be described by a rate constant $K_{ad}$. By preparing atoms at various temperatures and sweep the magnetic field close to the resonance, we map out the dependence of $L_{3}$ on both the magnetic field and the temperature. From such $L_3$ we extract, what we believe, a first experimental measurement of the temperature dependence of $K_{ad}(T)$. We find that $K_{ad}$ decreases with temperature in the ultracold regime, as predicted in [3], but with absolute values that differ from those of the universal quantum Langevin model [3], at least at this initial stage of analysis. [1] Tin-Lun Ho, Xiaoling Cui and Weiran Li, Phys. Rev. Lett., \textbf{108}, 250401, (2012) [2] E. L. Hazlett, Y. Zhang, R.W. Stites and K. M. O'Hara, Phys. Rev. Lett., \textbf{108}, 045304, (2012) [3] Bo Gao, Phys. Rev. Lett., \textbf{105}, 263203, (2010) [Preview Abstract] |
Wednesday, May 25, 2016 11:18AM - 11:30AM |
H7.00005: Harmonic trap resonance enhanced synthetic atomic spin-orbit coupling Ling-Na Wu, Xinyu Luo, Zhi-Fang Xu, Masahito Ueda, Ruquan Wang, Li You The widely adopted scheme for synthetic atomic spin-orbit coupling (SOC) is based on the momentum sensitive Raman coupling [1], which is easily implemented in one spatial dimension. Recently, schemes based on pulsed or periodically modulating gradient magnetic field (GMF) were proposed [2,3] and the main characteristic features have subsequently been demonstrated [4,5]. The present work reports an experimental discovery and the associated theoretical understanding of tuning the SOC strength synthesized with GMF through the motional resonance of atomic center-of-mass in a harmonic trap. In some limits, we observe up to 10 times stronger SOC compared to the momentum impulse from GMF for atoms in free space. \\\\ 1. Y.-J. Lin, et al, Nature \textbf{471}, 83 (2011).\\ 2. Z.-F. Xu, et al, Phys. Rev. A \textbf{87}, 063634 (2013). \\ 3. B. M. Anderson, et al, Phys. Rev. Lett. \textbf{111}, 125301 (2013).\\ 4. X. Luo, et al, Scientific Reports \textbf{6}, 18983 (2016). \\ 5. G. Jotzu, et al, Phys. Rev. Lett. \textbf{115}, 073002 (2015). [Preview Abstract] |
Wednesday, May 25, 2016 11:30AM - 11:42AM |
H7.00006: Lifetime of $^6$Li$^{40}$K dimers near a Feshbach resonance Michael Jag, Marko Cetina, Rianne Lous, Jesper Levinsen, Dmitry Petrov, Rudolf Grimm We investigate the lifetime of bosonic dimers formed in a Fermi- Fermi mixture of $^6$Li and $^{40}$K atoms near a Feshbach resonance. Pure dimer samples are created from a Li-K mixture by ramping a magnetic field across the resonance and removing unbound atoms. We then perform lifetime measurements using both trapped high-density as well as expanding low-density samples after release from the trap. These measurements discriminate between the spontaneous and the collisional dimer decay. We further determine the dimer decay due to Li-LiK collisions in an atom-dimer mixture. Our measurements reveal a more than three-fold (five-fold) decrease in decay due to dimer-dimer (atom-dimer) collisions as the Feshbach resonance is approached. This observation is in good agreement with a theoretical prediction, which relates the decay rate to the probability of finding the colliding atoms within a short distance, and can mostly be explained by the increased fermionic character of the halo-dimer state together with Pauli blocking. We apply our model to combinations of other fermionic species to predict the dimer lifetime, which is an important parameter for their prospect towards realizing novel quantum phases. [Preview Abstract] |
Wednesday, May 25, 2016 11:42AM - 11:54AM |
H7.00007: Photonic Landau levels on cones Nathan Schine, Albert Ryou, Andrey Gromov, Ariel Sommer, Jonathan Simon Creating photonic materials with nontrivial topological characteristics has seen burgeoning interest in recent years; however, a major route to topology, a magnetic field for continuum photons, has remained elusive. We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We will discuss the conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids. [Preview Abstract] |
Wednesday, May 25, 2016 11:54AM - 12:06PM |
H7.00008: Optical control of Magnetic Feshbach Resonances using Closed Channel EIT Arunkumar Jagannathan, Nithya Arunkumar, James Joseph, John Thomas Optical techniques can provide rapid temporal control and high-resolution spatial control of interactions in cold gases enabling the study of non-equilibrium strongly interacting Fermi gases. We use electromagnetically induced transparency (EIT) in the closed channel to control magnetic Feshbach resonances in an optically-trapped mixture of the two lowest hyperfine states of a $^{\mathrm{6}}$Li Fermi gas. In our experiments, the narrow Feshbach resonance is tuned by up to 3 G. For the broad resonance, the spontaneous lifetime is increased to 0.4 s at the dark state resonance, compared to 0.5 ms for single field tuning. We present a new model of light-induced loss spectra, employing continuum-dressed basis states, that agrees in shape and magnitude with loss measurements for both broad and narrow resonances. Using this model, we predict the trade-off between tunability and loss for the broad resonance in $^{\mathrm{6}}$Li, showing that our two-field method substantially reduces the two-body loss rate compared to single field methods for same tuning range. [Preview Abstract] |
Wednesday, May 25, 2016 12:06PM - 12:18PM |
H7.00009: Contact Tensor in a $p$-Wave Fermi Gas with Anisotropic Feshbach Resonances Shuhei M. Yoshida, Masahito Ueda Recent theoretical and experimental investigations have revealed that a Fermi gas with a p-wave Feshbach resonance has universal relations between the system's high-momentum behavior and thermodynamics. A new feature introduced by the p-wave interaction is anisotropy in the Feshbach resonances; three degenerate $p$-wave resonances split according to the magnetic quantum number of the closed-channel molecules $|m|$ due to the magnetic dipole-dipole interaction. Here, we investigate the consequences of the anisotropy. We show that the momentum distribution has a high-momentum asymptote $n_k \sim k^{-2} \sum_{m,m'=-1}^1 C_{m,m'}Y_1^{m\ast}(\hat{k}) Y_1^{m'}(\hat{k})$, in which we introduce the $p$-wave contact tensor $C_{m,m'}$. In contrast to the previous studies, it has nine components [1,2]. We identify them as the number, angular momentum, and nematicity of the closed-channel molecules. We also discuss two examples, the anisotropic $p$-wave superfluid and a gas confined in a cigar-shaped trap, which exhibit a nematicity component in the $p$-wave contact tensor. [1] S. M. Yoshida, and M. Ueda, Phys.~Rev.~Lett.~\textbf{115}, 135303 (2015). [2] Z. Yu, J. H. Thywissen, and S. Zhang, Phys.~Rev.~Lett.~\textbf{115}, 135304 (2015). [Preview Abstract] |
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