Bulletin of the American Physical Society
20th Annual Meeting of the APS Northwest Section
Volume 64, Number 9
Thursday–Saturday, May 16–18, 2019; Western Washington University, Bellingham, Washington
Session C1: Atomic, Molecular, and Optical I |
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Chair: Jeffrey McGuirk, Simon Fraser University Room: Viking Union 462A |
Friday, May 17, 2019 1:30PM - 2:00PM |
C1.00001: Collision Universalities and the Quantum Pressure Standard Invited Speaker: Kirk Madison Here we present recent work on two forms of universality in collision physics - universality refers to the existence of properties that are independent of short-range structural details. We discuss experimental observations of the universal and non-universal decay rate of ultra-cold, reactive molecules, and we report the discovery of a new form of universality for quantum diffractive collisions. We find that diffractive collisions, those that transfer the minimum energy allowed by quantum mechanics, are universal and that the energy transferred by them encodes information about the total collision cross section and the form of the interaction potential at long range. This universality phenomenon (which we refer to as QDU) is a manifestation of the Heisenberg uncertainty principle and a consequence of the collision induced particle localization. QDU occurs for any interaction and applies to collisions of both elementary and composite particles (e.g. nuclei, atoms and molecules). Using QDU for van der Waals interactions, we realize a self-defining cold atom sensor providing the first primary and quantum definition of pressure and particle flux for ultra-high vacuum applicable to any atomic or molecular species.\\ \\In collaboration with: Denis Uhland, Erik Fireling, Pinrui Shen, Roman Krems; Univ of British Columbia, James Booth, British Columbia Institute of Technology [Preview Abstract] |
Friday, May 17, 2019 2:00PM - 2:12PM |
C1.00002: Stable longitudinal spin domains in a nondegenerate ultracold gas S. D. Graham, D. Niroomand, J. M. McGuirk We demonstrate that linear effective magnetic fields can stabilize longitudinal spin domains in a weakly-interacting gas of $^{87}$Rb atoms above quantum degeneracy. Coherent spin-rotating interactions are modified by applying a small linear effective magnetic field that varies the local Larmor precession. Adding small linear effective magnetic fields with gradients that oppose the initial spin gradient in the domain wall stabilizes the spin domains. We experimentally determine these stabilizing gradients over a range of cloud temperatures and densities, and compare to a quantum Boltzmann theory in the hydrodynamic regime. [Preview Abstract] |
Friday, May 17, 2019 2:12PM - 2:24PM |
C1.00003: Dueling Dynamical Backaction in a Cryogenic Optomechanical Cavity Bradley D Hauer, Thomas J Clark, Paul H Kim, Callum Doolin, John P Davis Dynamical backaction has proven to be a versatile tool in cavity optomechanics, allowing for precise manipulation of a mechanical resonator's motion using confined optical photons. In my talk, I will present measurements of a silicon whispering-gallery-mode optomechanical cavity where backaction originates from opposing radiation-pressure and photothermal forces, with the former dictating the optomechanical spring effect and the latter governing the optomechanical damping. At high enough optical input powers, we show that the photothermal force drives the mechanical resonator into self-oscillations for a pump beam detuned to the low frequency (red) side of the optical resonance, contrary to what one would expect for a conventional radiation-pressure-dominated optomechanical device. Using a fully nonlinear model, we fit the hysteretic response of the optomechanical cavity to extract its properties, demonstrating that this non-sideband-resolved device exists in a regime where photothermal damping could be used to cool its motion to the quantum ground state. [Preview Abstract] |
Friday, May 17, 2019 2:24PM - 2:54PM |
C1.00004: Bogoliubov theory of the ground state and low-energy excitations of a Bose-Einstein condensate of rigid-rotor molecules Invited Speaker: Brandon Peden Via Bogoliubov mean-field theory, we investigate the dipolar properties of the ground state and low-energy excitations of a Bose-Einstein condensate of rigid rotor molecules confined harmonically to two dimensions. An external polarizing field is applied that induces molecular dipole moments, and the molecules interact via dipole-dipole interactions. Under large electric fields, we reproduce the well-known density-wave instability that arises in a fully polarized BEC. Under small applied fields, a global instability arises that is associated with the development of an in-plane component of the molecular dipole moment. This arises at interaction strengths far below those necessary to see a previously-predicted spin-wave to arise. The BEC is unstable in this regime, and the complex dispersion relations are anisotropic, reflecting the spontaneous breaking of azimuthal symmetry. The physical character of these instabilities is clarified via spin and density static structure factors.\\ \\In Collaboration with: Joseph Smith, University of Otago; Seth Rittenhouse, United States Naval Academy [Preview Abstract] |
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