Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E26: Bose-Einstein Condensates and Nonlinear Waves |
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Sponsoring Units: DAMOP Chair: Mark Edwards, Georgia Southern University Room: LACC 404A |
Tuesday, March 6, 2018 8:00AM - 8:12AM |
E26.00001: Photon thermalization and Bose condensation via laser cooling of atoms Chiao-Hsuan Wang, Michael Gullans, James Porto, William Phillips, Jacob Taylor The advent of laser cooling and trapping techniques for neutral atoms has led to remarkable breakthroughs in exploring the interaction between light and matter at ultracold temperatures. Here we focus on laser cooling from the perspective of the light --- specifically, the scattering of light between different optical modes in the presence of the cooling beams. In high optical depth atomic ensembles, we show that photons reemitted during the laser cooling process can equilibrate with the atomic motion and reach a steady state, and a grand canonical ensemble of photons can arise directly via atomic laser cooling in an experimentally accessible regime, with a chemical potential controlled by the laser frequency. Moreover, by placing the atoms in a curved cavity, the transverse modes in the cavity can be mapped into 2D massive bosons inside a parabolic well and can lead to 2D Bose-Einstein condensate of light. We consider realization of this regime using two-level atoms in Doppler cooling, and construct a phase diagram in the laser frequency and intensity parameter space showing the gain, condensate, thermal and quasi-thermal regimes for cavity photons with simulated values appropriate for the Yb intercombination transition. |
Tuesday, March 6, 2018 8:12AM - 8:24AM |
E26.00002: Bose–Einstein condensation and superfluidity of trapped photons with coordinate-dependent mass and interactions Oleg Berman, Roman Kezerashvili, Yurii Lozovik The condensate density profile of trapped two-dimensional gas of photons in an optical microcavity, filled by a dye solution, is obtained by taking into account coordinate dependence effective mass of cavity photons and photon–photon coupling parameter [1]. The profiles for the densities of the superfluid and normal phases of trapped photons in the different regions of the system at the fixed temperature are analyzed. The radial dependencies of local mean-field phase transition temperature and local Kosterlitz-Thouless transition temperature of superfluidity for trapped microcavity photons are demonstrated. The coordinate dependence of cavity photon effective mass and photon–photon coupling parameter is important for the mirrors of smaller radius with the high trapping frequency, which provides Bose-Einstein condensation and superfluidity for smaller critical number of photons at the same temperature. We discuss a possibility of an experimental study of the density profiles for the normal and superfluid components in the system under consideration. |
Tuesday, March 6, 2018 8:24AM - 8:36AM |
E26.00003: Trans-Planckian issues and Emergent Gravity: from Bose-Einstein condensates (BEC) to analogue black holes Supratik Sarkar, A. Bhattacharyay To account for the non-local interactions in a Bose-Einstein Condensate (BEC), an addition of a minimal correction term to the standard Gross-Pitaevskii model effectively can make the healing length (ξ) decrease more rapidly with the increase of s-wave scattering length (a). From analogue gravity perspectives, this shrinking of ξ via tuning a through Feshbach resonance, in principle, makes the short-wavelength (i.e. high energy) regime more accessible experimentally by pushing the Lorentz-breaking dispersion even more towards the UV side. The effects of the Lorentz-breaking quantum potential term in the BEC-dynamics on independent multiple scales can be captured through a UV-IR coupling of the phonon-excitation-modes of a massive minimally coupled Klein-Gordon field. The analysis was argued on a (3+1)D flat spacetime. The analysis is extended for a canonical acoustic black hole in a (3+1)D curved spacetime through presenting an analogue gravity model upto order(ξ2) accuracy. In our formalism, the growth rate of the large-wavelength secondary ω modes is found to hold the clue to extract the lost information regarding the short-wavelength primary ω1 modes. So this can actually reveal the relative abundance of the originally Hawking radiated quanta in a (3+1)D curved background. |
Tuesday, March 6, 2018 8:36AM - 8:48AM |
E26.00004: Localized Horizon Modes Partnered to Acoustic Hawking Emission in a Bose-Einstein Condensate Jonathan Curtis, Gil Refael, Victor Galitski We consider a superfluid condensate with a quasi-one-dimensional flow possessing an acoustic event horizon. In addition to the production of sonic Hawking radiation we find components of the eigenmodes which are localized onto the exterior of the sonic black-hole. The physical significance of these localized modes is discussed, with a particular emphasis on how they may affect the entanglement structure and information capacity of the sonic black-hole. |
Tuesday, March 6, 2018 8:48AM - 9:00AM |
E26.00005: On-demand Smooth Flow by Stirring a Racetrack Atom Circuit Olatunde Oladehin, Benjamin Eller, Charles Clark, Mark Edwards We studied how smooth flow can be produced by stirring an ultracold atom circuit consisting of a gaseous Bose--Einstein condensate (BEC) confined in a ``racetrack'' potential. We assume that the BEC is strongly confined in a horizontal plane by a vertical harmonic trap and, within this plane, subjected to an arbitrary two--dimensional potential using laser light. The racetrack potential is made up of two straight parallel channels of length L connected on both ends by semicircular channels of the same width and (energy) depth as the straightaways. We used the Gross--Pitaevskii equation (GPE) to simulate the behavior of the BEC in this potential when stirred by a rectangular paddle at various speeds and barrier heights. For fixed L we stirred the BEC at four different speeds and with barrier heights that varied from 0.5μ to 2.0μ. This series of conditions was performed for seven different values of L. We also devised a simple 1D model of the stirring of the BEC based on the GPE in order to understand how smooth flow is produced by stirring. This understanding should enable the design of a stirring sequence that would produce a given flow on demand. |
Tuesday, March 6, 2018 9:00AM - 9:12AM |
E26.00006: Finite-temperature Effects on Producing Smooth Flow in a Racetrack Atom Circuit Benjamin Eller, Olatunde Oladehin, Charles Clark, Mark Edwards We studied smooth flow produced by stirring an ultracold atom circuit consisting of a gaseous Bose--Einstein condensate (BEC) confined in a ``racetrack'' potential at finite temperature. The BEC is assumed to be strongly confined in a horizontal plane by a vertical harmonic trap and, within this plane, subjected to an arbitrary two--dimensional potential. The racetrack potential is made up of two straight parallel channels connected on both ends by semicircular channels of the same width and (energy) depth as the straightaways. We used the Zaremba--Nikuni--Griffin model to simulate the behavior of the BEC and noncondensate in this potential when stirred by a rectangular paddle at various speeds and barrier heights. We compare the amount of flow produced by stirring under these conditions with the flow produced under the same conditions but at zero temperature. We discuss how a simple model which predicts the flow produced by stirring at zero temperature could be modified for finite temperature. |
Tuesday, March 6, 2018 9:12AM - 9:24AM |
E26.00007: Nonlinear Band Spectrum and Elementary Excitations of a Bose Gas Within a Multi-Rods Structure Omar Rodriguez Lopez, Miguel Solis We calculate the ground state (gs) energy spectrum as well as the elementary excitations of a |
Tuesday, March 6, 2018 9:24AM - 9:36AM |
E26.00008: Absence of Landau damping in driven three-component Bose--Einstein condensate in optical lattices Gavril Shchedrin, Daniel Jaschke, Lincoln Carr Multicomponent Bose-Einstein condensates (BECs) are a unique form of matter that allow one to explore coherent many-body phenomena in a macroscopic quantum system by manipulating its internal degrees of freedom. The ground state of alkali-based BECs, which includes $^{7}{\rm Li}$, $^{23}{\rm Na}$, and $^{87}{\rm Rb}$, is characterized by the hyperfine spin $F$, that can be best probed in optical lattices, which liberate its $2F+1$ internal components and thus provides a direct access to its internal structure. We explore the quantum many-body physics of a three-component Bose-Einstein condensate in optical lattices driven by laser fields in $V$ and $\Lambda$ configurations. We obtain exact analytical expressions for the energy spectrum and amplitudes of elementary excitations, and discover symmetries among them. We demonstrate that the applied laser fields induce a gap in the otherwise gapless Bogoliubov spectrum. We find that Landau damping of the collective modes above the energy of the gap is carried by laser-induced roton modes and is considerably suppressed compared to the phonon-mediated damping endemic to undriven scalar condensates. |
Tuesday, March 6, 2018 9:36AM - 9:48AM |
E26.00009: Collective excitations of unconventional two-species Bose-Einstein condensation in the p-orbital bands of two-dimensional hybrid optical lattices I-Kang Liu, Shih-Chuan Gou Unconventional Bose-Einstein condensation (BEC) arising in the metastable high orbital states of a quantum many-body system has been a topical subject in the recent years [1-4]. Based on a modified imaginary-time propagation method in momentum space, we had previously investigated the unconventional BEC in the two-species mixture with p-wave symmetry in the second band of a bipartite optical lattice [1-3,5], and shown that such a system undergoes a phase transition from a complex staggered-orbital state to a real checkerboard-like spin-density state when the strength of inter-species interaction overtakes its intra-species counterpart. In this presentation, we follow up to study the stability of such unconventional BEC state in the bipartite square lattice and a hybrid square lattice [6] by looking into the properties of its collective excitations which are obtained by numerically solving the Bogoliubov-de-Genne equation. |
Tuesday, March 6, 2018 9:48AM - 10:00AM |
E26.00010: Splitting instability of a doubly quantized vortex in homogeneous superfluids Hiromitsu Takeuchi, Michikazu Kobayashi, Kenichi Kasamatsu We revisit the fundamental problem of splitting instability of a doubly-quantized |
Tuesday, March 6, 2018 10:00AM - 10:12AM |
E26.00011: Vortex lattices with multiple fluxes per unit cell in fast rotating dipolar Bose-Einstein condensates Szu-Cheng Cheng, Shih-Da Jheng A recently proposed wave function of vortex lattice, named as von Neumann lattice [1], is applied to examine the phases of vortex lattices in fast rotating dipolar Bose-Einstein condensates. The von Neumann lattice is a general vortex-lattice configuration which not only contains the Abrikosov lattice as a special case, but also bubble crystals [2] predicted numerically in the system. We applied von Neumann lattices to reexamine the vortex-lattice phases in fast rotating dipolar Bose-Einstein condensates. We find that vortex lattices with multiple fluxes per unit cell can be energetically stable inside the unstable regime predicted by vortex lattices with a single flux per unit cell [3]. |
Tuesday, March 6, 2018 10:12AM - 10:24AM |
E26.00012: SU(3) gauge field theory of spin-1 Bose-Einstein condensates Emi Yukawa, Masahito Ueda We reformulate hydrodynamic theory of spin-1 Bose-Einstein condensates (BEC) in terms of an SU(3) gauge field and describe the mean-field dynamics equivalent to the multicomponent Gross-Pitaevskii equations. In this theory, the spin vector and the nematic tensor constitute a single nine-component tensor which serves as an SU(3) gauge field and describes the spin-nematic texture in space and time. The constraints among the SU(3) gauge field imply the invariance of effective gauge potentials which encapsulate all effects of physical quantities and external fields. Compared with hydrodynamic theory, this new formulation greatly simplifies constraints on the gauge field and makes the derivation of hydrodynamic equations physically transparent. |
Tuesday, March 6, 2018 10:24AM - 10:36AM |
E26.00013: Infinite lattice of vortex molecules Beinat Mencia Uranga, Austen Lamacraft We study the ground state of a 2D rotating two component BEC in the presence of an external electromagnetic field that gives rise to Rabi oscillations in between the two components. The EM field works as a confinement mechanism of vortices leading to the formation of vortex molecules: pairs of vortices, one of each component. We study the full-blown problem by solving the Gross-Pitaevskii equation for an infinite system. We explain the result in terms of an effective theory of electric dipoles with 2D dipolar interactions. |
Tuesday, March 6, 2018 10:36AM - 10:48AM |
E26.00014: Hugenholtz-Pines theorem for Bose–Einstein condensates with internal degrees of freedom Shohei Watabe The Hugenholtz-Pines theorem for the spin-f spinor BEC with broken U(1)×SO(3) symmetry is an unsolved problem in the field of ultracold quantum gases since 1998 when the experiment of the spin-1 BEC was first realized, and its Bogoliubov theories were first proposed. In this presentation, we will propose the Hugenholtz-Pines theorem for BECs with internal degrees of freedom. In order to that, we clarified the generalized version of the Hugenholtz-Pines theorem for BECs with broken U(1)×SO(N) or U(1)×SU(N) symmetry in the presence of the SO(N) or SU(N) symmetry breaking external fields. This theorem serves to deductively organize the Hugenhotlz-Pines theorem for spin-f spinor BECs in the presence of an external magnetic field. We will introduce some specific results of the Hugenholtz-Pines theorem in certain phases of the spin-1 or spin-2 BEC. |
Tuesday, March 6, 2018 10:48AM - 11:00AM |
E26.00015: Bose-Einstein condensation of a non-ideal Bose gas of atoms with large spin Andrei Pavlov, Vladimir Babichenko, Ilya Polishchuk
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