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An FA, Sundar B, Hou J, Luo XW, Meier EJ, Zhang C, Hazzard KRA, Gadway B. Nonlinear Dynamics in a Synthetic Momentum-State Lattice. PHYSICAL REVIEW LETTERS 2021; 127:130401. [PMID: 34623847 DOI: 10.1103/physrevlett.127.130401] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 08/27/2021] [Indexed: 06/13/2023]
Abstract
The scope of analog simulation in atomic, molecular, and optical systems has expanded greatly over the past decades. Recently, the idea of synthetic dimensions-in which transport occurs in a space spanned by internal or motional states coupled by field-driven transitions-has played a key role in this expansion. While approaches based on synthetic dimensions have led to rapid advances in single-particle Hamiltonian engineering, strong interaction effects have been conspicuously absent from most synthetic dimensions platforms. Here, in a lattice of coupled atomic momentum states, we show that atomic interactions result in large and qualitative changes to dynamics in the synthetic dimension. We explore how the interplay of nonlinear interactions and coherent tunneling enriches the dynamics of a one-band tight-binding model giving rise to macroscopic self-trapping and phase-driven Josephson dynamics with a nonsinusoidal current-phase relationship, which can be viewed as stemming from a nonlinear band structure arising from interactions.
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Affiliation(s)
- Fangzhao Alex An
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA
| | - Bhuvanesh Sundar
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
- JILA, Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - Junpeng Hou
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
| | - Xi-Wang Luo
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
| | - Eric J Meier
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA
| | - Chuanwei Zhang
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
| | - Kaden R A Hazzard
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - Bryce Gadway
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA
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Bighin G, Defenu N, Nándori I, Salasnich L, Trombettoni A. Berezinskii-Kosterlitz-Thouless Paired Phase in Coupled XY Models. PHYSICAL REVIEW LETTERS 2019; 123:100601. [PMID: 31573277 DOI: 10.1103/physrevlett.123.100601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Indexed: 06/10/2023]
Abstract
We study the effect of a linear tunneling coupling between two-dimensional systems, each separately exhibiting the topological Berezinskii-Kosterlitz-Thouless (BKT) transition. In the uncoupled limit, there are two phases: one where the one-body correlation functions are algebraically decaying and the other with exponential decay. When the linear coupling is turned on, a third BKT-paired phase emerges, in which one-body correlations are exponentially decaying, while two-body correlation functions exhibit power-law decay. We perform numerical simulations in the paradigmatic case of two coupled XY models at finite temperature, finding evidences that for any finite value of the interlayer coupling, the BKT-paired phase is present. We provide a picture of the phase diagram using a renormalization group approach.
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Affiliation(s)
- Giacomo Bighin
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria
| | - Nicolò Defenu
- Institut für Theoretische Physik, Universität Heidelberg, D-69120 Heidelberg, Germany
| | - István Nándori
- MTA-DE Particle Physics Research Group, P.O.Box 51, H-4001 Debrecen, Hungary
- MTA Atomki, P.O.Box 51, H-4001 Debrecen, Hungary
- University of Debrecen, P.O.Box 105, H-4010 Debrecen, Hungary
| | - Luca Salasnich
- Dipartimento di Fisica e Astronomia "Galileo Galilei," Università di Padova, Via Marzolo 8, 35131 Padova, Italy
- Istituto Nazionale di Ottica (INO) del Consiglio Nazionale delle Ricerche (CNR), Sezione di Sesto Fiorentino, Via Nello Carrara 2, 50019 Sesto Fiorentino, Italy
| | - Andrea Trombettoni
- CNR-IOM DEMOCRITOS Simulation Center, Via Bonomea 265, I-34136 Trieste, Italy
- SISSA and INFN, Sezione di Trieste, Via Bonomea 265, I-34136 Trieste, Italy
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Abstract
We present a field-theory description of ultracold bosonic atoms in the presence of a disordered external potential. By means of functional integration techniques, we aim to investigate and review the interplay between disordered energy landscapes and fluctuations, both thermal and quantum ones. Within the broken-symmetry phase, up to the Gaussian level of approximation, the disorder contribution crucially modifies both the condensate depletion and the superfluid response. Remarkably, it is found that the ordered (i.e., superfluid) phase can be destroyed also in regimes where the random external potential is suitable for a perturbative analysis. We analyze the simplest case of quenched disorder and then we move to present the implementation of the replica trick for ultracold bosonic systems. In both cases, we discuss strengths and limitations of the reviewed approach, paying specific attention to possible extensions and the most recent experimental outputs.
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Aidelsburger M, Ville JL, Saint-Jalm R, Nascimbène S, Dalibard J, Beugnon J. Relaxation Dynamics in the Merging of N Independent Condensates. PHYSICAL REVIEW LETTERS 2017; 119:190403. [PMID: 29219502 DOI: 10.1103/physrevlett.119.190403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Indexed: 06/07/2023]
Abstract
Controlled quantum systems such as ultracold atoms can provide powerful platforms to study nonequilibrium dynamics of closed many-body quantum systems, especially since a complete theoretical description is generally challenging. In this Letter, we present a detailed study of the rich out-of-equilibrium dynamics of an adjustable number N of uncorrelated condensates after connecting them in a ring-shaped optical trap. We observe the formation of long-lived supercurrents and confirm the scaling of their winding number with N in agreement with the geodesic rule. Moreover, we provide insight into the microscopic mechanism that underlies the smoothening of the phase profile.
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Affiliation(s)
- M Aidelsburger
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 place Marcelin-Berthelot, 75005 Paris, France
| | - J L Ville
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 place Marcelin-Berthelot, 75005 Paris, France
| | - R Saint-Jalm
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 place Marcelin-Berthelot, 75005 Paris, France
| | - S Nascimbène
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 place Marcelin-Berthelot, 75005 Paris, France
| | - J Dalibard
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 place Marcelin-Berthelot, 75005 Paris, France
| | - J Beugnon
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 place Marcelin-Berthelot, 75005 Paris, France
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5
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Krieg J, Kopietz P. Dual lattice functional renormalization group for the Berezinskii-Kosterlitz-Thouless transition: Irrelevance of amplitude and out-of-plane fluctuations. Phys Rev E 2017; 96:042107. [PMID: 29347532 DOI: 10.1103/physreve.96.042107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Indexed: 06/07/2023]
Abstract
We develop a functional renormalization group (FRG) approach for the two-dimensional XY model by combining the lattice FRG proposed by Machado and Dupuis [Phys. Rev. E 82, 041128 (2010)PLEEE81539-375510.1103/PhysRevE.82.041128] with a duality transformation that explicitly introduces vortices via an integer-valued field. We show that the hierarchy of FRG flow equations for the infinite set of relevant and marginal couplings of the model can be reduced to the well-known Kosterlitz-Thouless renormalization group equations for the renormalized temperature and the vortex fugacity. Within our approach it is straightforward to include weak amplitude as well as out-of-plane fluctuations of the spins, which lead to additional interactions between the vortices that do not spoil the Berezinskii-Kosterlitz-Thouless transition. This demonstrates that previous failures to obtain a line of true fixed points within the FRG are a mathematical artifact of insufficient truncation schemes.
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Affiliation(s)
- Jan Krieg
- Institut für Theoretische Physik, Universität Frankfurt, Max-von-Laue Strasse 1, 60438 Frankfurt, Germany
| | - Peter Kopietz
- Institut für Theoretische Physik, Universität Frankfurt, Max-von-Laue Strasse 1, 60438 Frankfurt, Germany
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6
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Bighin G, Salasnich L. Vortices and antivortices in two-dimensional ultracold Fermi gases. Sci Rep 2017; 7:45702. [PMID: 28374762 PMCID: PMC5379560 DOI: 10.1038/srep45702] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 03/03/2017] [Indexed: 11/09/2022] Open
Abstract
Vortices are commonly observed in the context of classical hydrodynamics: from whirlpools after stirring the coffee in a cup to a violent atmospheric phenomenon such as a tornado, all classical vortices are characterized by an arbitrary circulation value of the local velocity field. On the other hand the appearance of vortices with quantized circulation represents one of the fundamental signatures of macroscopic quantum phenomena. In two-dimensional superfluids quantized vortices play a key role in determining finite-temperature properties, as the superfluid phase and the normal state are separated by a vortex unbinding transition, the Berezinskii-Kosterlitz-Thouless transition. Very recent experiments with two-dimensional superfluid fermions motivate the present work: we present theoretical results based on the renormalization group showing that the universal jump of the superfluid density and the critical temperature crucially depend on the interaction strength, providing a strong benchmark for forthcoming investigations.
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Affiliation(s)
- G Bighin
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria
| | - L Salasnich
- Dipartimento di Fisica e Astronomia "Galileo Galilei" and CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy.,Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy
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7
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Choi JY, Seo SW, Shin YI. Observation of thermally activated vortex pairs in a quasi-2D Bose gas. PHYSICAL REVIEW LETTERS 2013; 110:175302. [PMID: 23679741 DOI: 10.1103/physrevlett.110.175302] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Indexed: 06/02/2023]
Abstract
We measure the in-plane distribution of thermally activated vortices in a trapped quasi-2D Bose gas, where we enhance the visibility of density-depleted vortex cores by radially compressing the sample before releasing the trap. The pairing of vortices is revealed by the two-vortex spatial correlation function obtained from the vortex distribution. The vortex density decreases gradually as temperature is lowered, and below a certain temperature, a vortex-free region emerges in the center of the sample. This shows the crossover from a Berezinskii-Kosterlitz-Thouless phase containing vortex-pair excitations to a vortex-free Bose-Einstein condensate in a finite-size 2D system.
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Affiliation(s)
- Jae-yoon Choi
- Center for Subwavelength Optics and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
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8
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Mashayekhi MS, Bernier JS, Borzov D, Song JL, Zhou F. Two-dimensional Bose gases near resonance: competing two-body and three-body effects. PHYSICAL REVIEW LETTERS 2013; 110:145301. [PMID: 25167002 DOI: 10.1103/physrevlett.110.145301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 01/23/2013] [Indexed: 06/03/2023]
Abstract
We report in this Letter the results of our investigation of 2D Bose gases beyond the dilute limit emphasizing the role played by three-body scattering events. We demonstrate that a competition between three-body attractive interactions and two-body repulsive forces results in the chemical potential of 2D Bose gases to exhibit a maximum at a critical scattering length beyond which these quantum gases possess a negative compressibility. For larger scattering lengths, the increasingly prominent role played by three-body attractive interactions leads to an onset instability at a second critical value. The three-body effects studied here are universal, fully characterized by the effective 2D scattering length a(2D) (or the size of the 2D bound states) and are, in comparison to the 3D case, independent of three-body ultraviolet physics. We find, within our approach, the ratios of the contribution to the chemical potential due to three-body interactions to the one due to two-body to be 0.27 near the maximum of the chemical potential and 0.73 in the vicinity of the onset instability.
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Affiliation(s)
- Mohammad S Mashayekhi
- Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z1, Canada
| | - Jean-Sébastien Bernier
- Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z1, Canada
| | - Dmitry Borzov
- Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z1, Canada
| | - Jun-Liang Song
- Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-6020 Innsbruck, Austria
| | - Fei Zhou
- Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z1, Canada
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9
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Iazzi M, Bassan N, Trombettoni A, Schmidt KE, Fantoni S. Vortex lines distribution in inhomogeneous lattices. Mol Phys 2011. [DOI: 10.1080/00268976.2011.637083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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10
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van der Bijl E, Duine RA. Anomalous Hall conductivity from the dipole mode of spin-orbit-coupled cold-atom systems. PHYSICAL REVIEW LETTERS 2011; 107:195302. [PMID: 22181618 DOI: 10.1103/physrevlett.107.195302] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Indexed: 05/31/2023]
Abstract
Motivated by recent experiments by Lin et al., [Nature (London) 471, 83 (2011)] that engineered spin-orbit coupling in ultracold mixtures of bosonic atoms, we study the dipole oscillation of trapped spin-orbit-coupled noncondensed Bose and Fermi gases. We find that different directions of oscillation are coupled by the spin-orbit interactions. The phase difference between oscillatory motion in orthogonal directions and the trapping frequencies of the modes are shown to be related to the anomalous Hall conductivity. Our results can be used to experimentally determine the anomalous Hall conductivity for cold-atom systems.
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Affiliation(s)
- E van der Bijl
- Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands
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11
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Chen D, White M, Borries C, DeMarco B. Quantum quench of an atomic Mott insulator. PHYSICAL REVIEW LETTERS 2011; 106:235304. [PMID: 21770517 DOI: 10.1103/physrevlett.106.235304] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 05/13/2011] [Indexed: 05/31/2023]
Abstract
We study quenches across the Bose-Hubbard Mott-insulator-to-superfluid quantum phase transition by using an ultracold atomic gas trapped in an optical lattice. Quenching from the Mott insulator to the superfluid phase is accomplished by continuously tuning the ratio of Hubbard tunneling to interaction energy. Excitations of the condensate formed after the quench are measured by using time-of-flight imaging. We observe that the degree of excitation is proportional to the fraction of atoms that cross the phase boundary and that the quantity of excitations and energy produced during the quench have a power-law dependence on the quench rate. These phenomena suggest an excitation process analogous to the Kibble-Zurek mechanism for defect generation in nonequilibrium classical phase transitions.
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Affiliation(s)
- David Chen
- Department of Physics, University of Illinois, 1110 West Green Street, Urbana, Illinois 61801, USA
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12
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Narayana S, Sato Y. Quantum coherence in a superfluid Josephson junction. PHYSICAL REVIEW LETTERS 2011; 106:055302. [PMID: 21405406 DOI: 10.1103/physrevlett.106.055302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 01/11/2011] [Indexed: 05/30/2023]
Abstract
We report a new kind of experiment in which we take an array of nanoscale apertures that form a superfluid (4)He Josephson junction and apply quantum phase gradients directly along the array. We observe collective coherent behaviors from aperture elements, leading to quantum interference. Connections to superconducting and Bose-Einstein condensate Josephson junctions as well as phase coherence among the superfluid aperture array are discussed.
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Affiliation(s)
- Supradeep Narayana
- The Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts 02142, USA
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13
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Observation of scale invariance and universality in two-dimensional Bose gases. Nature 2011; 470:236-9. [PMID: 21270797 DOI: 10.1038/nature09722] [Citation(s) in RCA: 200] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 12/01/2010] [Indexed: 11/09/2022]
Abstract
The collective behaviour of a many-body system near a continuous phase transition is insensitive to the details of its microscopic physics; for example, thermodynamic observables follow generalized scaling laws near the phase transition. The Berezinskii-Kosterlitz-Thouless (BKT) phase transition in two-dimensional Bose gases presents a particularly interesting case because the marginal dimensionality and intrinsic scaling symmetry result in a broad fluctuation regime and an extended range of universal scaling behaviour. Studies of the BKT transition in cold atoms have stimulated great interest in recent years, but a clear demonstration of critical behaviour near the phase transition has remained elusive. Here we report in situ density and density-fluctuation measurements of two-dimensional Bose gases of caesium at different temperatures and interaction strengths, observing scale-invariant, universal behaviours. The extracted thermodynamic functions confirm the existence of a wide universal region near the BKT phase transition, and provide a sensitive test of the universality predicted by classical-field theory and quantum Monte Carlo calculations. Our experimental results provide evidence for growing density-density correlations in the fluctuation region, and call for further explorations of universal phenomena in classical and quantum critical physics.
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14
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Krüger P, Hofferberth S, Mazets IE, Lesanovsky I, Schmiedmayer J. Weakly interacting Bose gas in the one-dimensional limit. PHYSICAL REVIEW LETTERS 2010; 105:265302. [PMID: 21231675 DOI: 10.1103/physrevlett.105.265302] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 09/18/2010] [Indexed: 05/30/2023]
Abstract
We prepare a chemically and thermally one-dimensional (1D) quantum degenerate Bose gas in a single microtrap. We introduce a new interferometric method to distinguish the quasicondensate fraction of the gas from the thermal cloud at finite temperature. We reach temperatures down to kT≈0.5ℏω(⊥) (transverse oscillator eigenfrequency ω(⊥)) when collisional thermalization slows down as expected in 1D. At the lowest temperatures the transverse-momentum distribution exhibits a residual dependence on the line density n(1D), characteristic for 1D systems. For very low densities the approach to the transverse single-particle ground state is linear in n(1D).
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Affiliation(s)
- P Krüger
- Midlands Ultracold Atom Research Centre (MUARC), School of Physics and Astronomy, The University of Nottingham, Nottingham, United Kingdom
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15
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Tung S, Lamporesi G, Lobser D, Xia L, Cornell EA. Observation of the presuperfluid regime in a two-dimensional Bose gas. PHYSICAL REVIEW LETTERS 2010; 105:230408. [PMID: 21231437 DOI: 10.1103/physrevlett.105.230408] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2010] [Revised: 09/14/2010] [Indexed: 05/30/2023]
Abstract
In complementary images of coordinate-space and momentum-space density in a trapped 2D Bose gas, we observe the emergence of presuperfluid behavior. As phase-space density ρ increases toward degenerate values, we observe a gradual divergence of the compressibility κ from the value predicted by a bare-atom model, κ(ba). κ/κ(ba) grows to 1.7 before ρ reaches the value for which we observe the sudden emergence of a spike at p = 0 in momentum space. Momentum-space images are acquired by means of a 2D focusing technique. Our data represent the first observation of non-mean-field physics in the presuperfluid but degenerate 2D Bose gas.
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Affiliation(s)
- S Tung
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440, USA
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16
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Cirac JI, Maraner P, Pachos JK. Cold atom simulation of interacting relativistic quantum field theories. PHYSICAL REVIEW LETTERS 2010; 105:190403. [PMID: 21231152 DOI: 10.1103/physrevlett.105.190403] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Indexed: 05/30/2023]
Abstract
We demonstrate that Dirac fermions self-interacting or coupled to dynamic scalar fields can emerge in the low energy sector of designed bosonic and fermionic cold atom systems. We illustrate this with two examples defined in two spacetime dimensions. The first one is the self-interacting Thirring model. The second one is a model of Dirac fermions coupled to a dynamic scalar field that gives rise to the Gross-Neveu model. The proposed cold atom experiments can be used to probe spectral or correlation properties of interacting quantum field theories thereby presenting an alternative to lattice gauge theory simulations.
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Affiliation(s)
- J Ignacio Cirac
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany
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17
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Powell S, Barnett R, Sensarma R, Das Sarma S. Interacting Hofstadter spectrum of atoms in an artificial gauge field. PHYSICAL REVIEW LETTERS 2010; 104:255303. [PMID: 20867393 DOI: 10.1103/physrevlett.104.255303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 06/01/2010] [Indexed: 05/29/2023]
Abstract
Motivated by experimental advances in the synthesis of gauge potentials for ultracold atoms, we consider the superfluid phase of interacting bosons on a square lattice in the presence of a magnetic field. We show that superfluid order implies spatial symmetry breaking, and predict clear signatures of many-body effects in time-of-flight measurements. By developing a Bogoliubov expansion based on the exact Hofstadter spectrum, we find the dispersion of the quasiparticle modes within the superfluid phase, and describe the consequences for Bragg spectroscopy measurements. The theory also provides an estimate of the critical interaction strength at the transition to the Mott insulator phase.
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Affiliation(s)
- Stephen Powell
- Joint Quantum Institute and Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
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18
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Lamporesi G, Catani J, Barontini G, Nishida Y, Inguscio M, Minardi F. Scattering in mixed dimensions with ultracold gases. PHYSICAL REVIEW LETTERS 2010; 104:153202. [PMID: 20481985 DOI: 10.1103/physrevlett.104.153202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Indexed: 05/29/2023]
Abstract
We experimentally investigate the mix-dimensional scattering occurring when the collisional partners live in different dimensions. We employ a binary mixture of ultracold atoms and exploit a species-selective 1D optical lattice to confine only one atomic species in 2D. By applying an external magnetic field in proximity of a Feshbach resonance, we adjust the free-space scattering length to observe a series of resonances in mixed dimensions. By monitoring 3-body inelastic losses, we measure the magnetic field values corresponding to the mix-dimensional scattering resonances and find a good agreement with the theoretical predictions based on simple energy considerations.
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Affiliation(s)
- G Lamporesi
- European Laboratory for Nonlinear Spectroscopy and Dipartimento di Fisica, Università di Firenze, via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
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19
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Williams RA, Al-Assam S, Foot CJ. Observation of vortex nucleation in a rotating two-dimensional lattice of Bose-Einstein condensates. PHYSICAL REVIEW LETTERS 2010; 104:050404. [PMID: 20366752 DOI: 10.1103/physrevlett.104.050404] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Indexed: 05/29/2023]
Abstract
We report the observation of vortex nucleation in a rotating optical lattice. A 87Rb Bose-Einstein condensate was loaded into a static two-dimensional lattice and the rotation frequency of the lattice was then increased from zero. We studied how vortex nucleation depended on optical lattice depth and rotation frequency. For deep lattices above the chemical potential of the condensate we observed a linear dependence of the number of vortices created with the rotation frequency, even below the thermodynamic critical frequency required for vortex nucleation. At these lattice depths the system formed an array of Josephson-coupled condensates. The effective magnetic field produced by rotation introduced characteristic relative phases between neighboring condensates, such that vortices were observed upon ramping down the lattice depth and recombining the condensates.
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Affiliation(s)
- R A Williams
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom
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20
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Cladé P, Ryu C, Ramanathan A, Helmerson K, Phillips WD. Observation of a 2D Bose gas: from thermal to quasicondensate to superfluid. PHYSICAL REVIEW LETTERS 2009; 102:170401. [PMID: 19518764 DOI: 10.1103/physrevlett.102.170401] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Indexed: 05/27/2023]
Abstract
We present experimental results on a Bose gas in a quasi-2D geometry near the Berezinskii, Kosterlitz, and Thouless (BKT) transition temperature. By measuring the density profile after time of flight and the coherence length, we identify different states of the gas. We observe that the gas develops a bimodal distribution without long range order. In this regime, the gas presents a longer coherence length than the thermal cloud; it is quasicondensed but is not superfluid. Experimental evidence indicates that we also observe the superfluid transition (BKT transition). For a sufficiently long time of flight, we observe a trimodal distribution when the gas has developed a superfluid component.
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Affiliation(s)
- P Cladé
- Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8424, USA
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Chang JJ, Engels P, Hoefer MA. Formation of dispersive shock waves by merging and splitting Bose-Einstein condensates. PHYSICAL REVIEW LETTERS 2008; 101:170404. [PMID: 18999726 DOI: 10.1103/physrevlett.101.170404] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Indexed: 05/27/2023]
Abstract
The processes of merging and splitting dilute-gas Bose-Einstein condensates are studied in the nonadiabatic, high-density regime. Rich dynamics are found. Depending on the experimental parameters, uniform soliton trains containing more than ten solitons or the formation of a high-density bulge as well as dispersive shock waves are observed experimentally within merged BECs. Our numerical simulations indicate the formation of many vortex rings. In the case of splitting a BEC, the transition from sound-wave formation to dispersive shock-wave formation is studied by use of increasingly stronger splitting barriers. These experiments realize prototypical dispersive shock situations.
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Affiliation(s)
- J J Chang
- Washington State University, Department of Physics and Astronomy, Pullman, Washington, D.C. 99164, USA
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Terhalle B, Richter T, Desyatnikov AS, Neshev DN, Krolikowski W, Kaiser F, Denz C, Kivshar YS. Observation of multivortex solitons in photonic lattices. PHYSICAL REVIEW LETTERS 2008; 101:013903. [PMID: 18764113 DOI: 10.1103/physrevlett.101.013903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Indexed: 05/26/2023]
Abstract
We report on the first observation of topologically stable spatially localized multivortex solitons generated in optically induced hexagonal photonic lattices. We demonstrate that topological stabilization of such nonlinear localized states can be achieved through self-trapping of truncated two-dimensional Bloch waves and confirm our experimental results by numerical simulations of the beam propagation in weakly deformed lattice potentials in anisotropic photorefractive media.
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Affiliation(s)
- Bernd Terhalle
- Nonlinear Physics Center and Laser Physics Center, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia
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Holzmann M, Krauth W. Kosterlitz-Thouless transition of the quasi-two-dimensional trapped Bose gas. PHYSICAL REVIEW LETTERS 2008; 100:190402. [PMID: 18518427 DOI: 10.1103/physrevlett.100.190402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 03/06/2008] [Indexed: 05/26/2023]
Abstract
We use quantum Monte Carlo methods to compute the density profile, the nonclassical moment of inertia, and the condensate fraction of an interacting quasi-two-dimensional trapped Bose gas with up to N ~ 5 x 10(5) atoms and parameters closely related to recent experiments. We locate the Kosterlitz-Thouless temperature T(KT) and discuss intrinsic signatures of the onset of superfluidity in the density profile. Below T(KT), the condensate fraction is macroscopic even for our largest systems and decays only slowly with system size. We show that the thermal population of excited states in the transverse direction changes the two-dimensional density profile noticeably in both the normal and the superfluid phase.
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