1
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Extended Bose-Hubbard Model with Cavity-Mediated Infinite-Range Interactions at Finite Temperatures. Sci Rep 2020; 10:9076. [PMID: 32494030 PMCID: PMC7270117 DOI: 10.1038/s41598-020-66054-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 05/14/2020] [Indexed: 11/29/2022] Open
Abstract
We consider the finite-temperature properties of the extended Bose-Hubbard model realized recently in an ETH experiment [Nature 532, 476 (2016)]. Competing short- and global-range interactions accommodate fascinating collective phenomena. We formulate a self-consistent mean-field theory to describe the behaviors of the system at finite temperatures. At a fixed chemical potential, we map out the distributions of the superfluid order parameters and number densities with respect to the temperatures. For a charge density wave, we find that the global-range interaction enhances the charge order by increasing the transition temperature at which the charge order melts out, while for a supersolid phase, we find that the disappearance of the charge order and the superfluid order occurs at different temperature. At a fixed number-density filling factor, we extract the temperature dependence of the thermodynamic functions such as internal energy, specific heat and entropy. Across the superfluid phase transition, the specific heat has a discontinuous jump.
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2
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Ostermann S, Niedenzu W, Ritsch H. Unraveling the Quantum Nature of Atomic Self-Ordering in a Ring Cavity. PHYSICAL REVIEW LETTERS 2020; 124:033601. [PMID: 32031825 DOI: 10.1103/physrevlett.124.033601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Indexed: 06/10/2023]
Abstract
Atomic self-ordering to a crystalline phase in optical resonators is a consequence of the intriguing nonlinear dynamics of strongly coupled atom motion and photons. Generally the resulting phase diagrams and atomic states can be largely understood on a mean-field level. However, close to the phase transition point, quantum fluctuations and atom-field entanglement play a key role and initiate the symmetry breaking. Here we propose a modified ring cavity geometry, in which the asymmetry imposed by a tilted pump beam reveals clear signatures of quantum dynamics even in a larger regime around the phase transition point. Quantum fluctuations become visible both in the dynamic and steady-state properties. Most strikingly we can identify a regime where a mean-field approximation predicts a runaway instability, while in the full quantum model the quantum fluctuations of the light field modes stabilize uniform atomic motion. The proposed geometry thus allows to unveil the "quantumness" of atomic self-ordering via experimentally directly accessible quantities.
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Affiliation(s)
- Stefan Ostermann
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21a, A-6020 Innsbruck, Austria
| | - Wolfgang Niedenzu
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21a, A-6020 Innsbruck, Austria
| | - Helmut Ritsch
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21a, A-6020 Innsbruck, Austria
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3
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Laske T, Winter H, Hemmerich A. Pulse Delay Time Statistics in a Superradiant Laser with Calcium Atoms. PHYSICAL REVIEW LETTERS 2019; 123:103601. [PMID: 31573286 DOI: 10.1103/physrevlett.123.103601] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2019] [Indexed: 06/10/2023]
Abstract
Cold samples of calcium atoms are prepared in the metastable ^{3}P_{1} state inside an optical cavity resonant with the narrow band (375 Hz) ^{1}S_{0}→^{3}P_{1} intercombination line at 657 nm. We observe a superradiant emission of hyperbolic secant shaped pulses into the cavity with an intensity proportional to the square of the atom number, a duration much shorter than the natural lifetime of the ^{3}P_{1} state, and a delay time fluctuating from shot to shot in excellent agreement with theoretical predictions. Our incoherent pumping scheme to produce inversion on the ^{1}S_{0}→^{3}P_{1} transition should be extendable to allow for continuous wave laser operation.
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Affiliation(s)
- Torben Laske
- Institut für Laser-Physik and Zentrum für Optische Quantentechnologien, Universität Hamburg, D-22761 Hamburg, Germany
| | - Hannes Winter
- Institut für Laser-Physik and Zentrum für Optische Quantentechnologien, Universität Hamburg, D-22761 Hamburg, Germany
| | - Andreas Hemmerich
- Institut für Laser-Physik and Zentrum für Optische Quantentechnologien, Universität Hamburg, D-22761 Hamburg, Germany
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4
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Georges C, Cosme JG, Mathey L, Hemmerich A. Light-Induced Coherence in an Atom-Cavity System. PHYSICAL REVIEW LETTERS 2018; 121:220405. [PMID: 30547631 DOI: 10.1103/physrevlett.121.220405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Indexed: 06/09/2023]
Abstract
We demonstrate a light-induced formation of coherence in a cold atomic gas system that utilizes the suppression of a competing density wave (DW) order. The condensed atoms are placed in an optical cavity and pumped by an external optical standing wave, which induces a long-range interaction mediated by photon scattering and a resulting DW order above a critical pump strength. We show that the light-induced temporal modulation of the pump wave can suppress this DW order and restore coherence. This establishes a foundational principle of dynamical control of competing orders analogous to a hypothesized mechanism for light-induced superconductivity in high-T_{c} cuprates.
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Affiliation(s)
- Christoph Georges
- Institut für Laser-Physik and Zentrum für Optische Quantentechnologien, Universität Hamburg, D-22761 Hamburg, Germany
| | - Jayson G Cosme
- Institut für Laser-Physik and Zentrum für Optische Quantentechnologien, Universität Hamburg, D-22761 Hamburg, Germany
- The Hamburg Center of Ultrafast Imaging, Luruper Chaussee 149, D-22761 Hamburg, Germany
| | - Ludwig Mathey
- Institut für Laser-Physik and Zentrum für Optische Quantentechnologien, Universität Hamburg, D-22761 Hamburg, Germany
- The Hamburg Center of Ultrafast Imaging, Luruper Chaussee 149, D-22761 Hamburg, Germany
| | - Andreas Hemmerich
- Institut für Laser-Physik and Zentrum für Optische Quantentechnologien, Universität Hamburg, D-22761 Hamburg, Germany
- The Hamburg Center of Ultrafast Imaging, Luruper Chaussee 149, D-22761 Hamburg, Germany
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5
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Wolf P, Schuster SC, Schmidt D, Slama S, Zimmermann C. Observation of Subradiant Atomic Momentum States with Bose-Einstein Condensates in a Recoil Resolving Optical Ring Resonator. PHYSICAL REVIEW LETTERS 2018; 121:173602. [PMID: 30411934 DOI: 10.1103/physrevlett.121.173602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Indexed: 06/08/2023]
Abstract
We experimentally investigate the formation of subradiant atomic momentum states in Bose-Einstein condensates inside a recoil resolving optical ring resonator according to the theoretical proposal of Cola, Bigerni, and Piovella. The atoms are pumped from the side with laser light that contains two frequency components. They resonantly drive cavity assisted Raman transitions between three discreet atomic momentum states. Within a few hundred microseconds, the system evolves into a stationary subradiant state. In this state, the condensate develops two density gratings suitable to diffract the two frequency components of the pump field into the resonator. Both components destructively interfere such that scattering is efficiently suppressed. A series of subradiant states for various amplitude ratios of the two pump components between 0 and 2.1 have been observed. The results are well explained with a three state quantum model in mean field approximation.
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Affiliation(s)
- P Wolf
- Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - S C Schuster
- Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - D Schmidt
- Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - S Slama
- Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
| | - C Zimmermann
- Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
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6
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Kroeze RM, Guo Y, Vaidya VD, Keeling J, Lev BL. Spinor Self-Ordering of a Quantum Gas in a Cavity. PHYSICAL REVIEW LETTERS 2018; 121:163601. [PMID: 30387632 DOI: 10.1103/physrevlett.121.163601] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Indexed: 06/08/2023]
Abstract
We observe the joint spin-spatial (spinor) self-organization of a two-component Bose-Einstein condensate (BEC) strongly coupled to an optical cavity. This unusual nonequilibrium Hepp-Lieb-Dicke phase transition is driven by an off-resonant Raman transition formed from a classical pump field and the emergent quantum dynamical cavity field. This mediates a spinor-spinor interaction that, above a critical strength, simultaneously organizes opposite spinor states of the BEC on opposite checkerboard configurations of an emergent 2D lattice. The resulting spinor density-wave polariton condensate is observed by directly detecting the atomic spin and momentum state and by holographically reconstructing the phase of the emitted cavity field. The latter provides a direct measure of the spin state, and a spin-spatial domain wall is observed. The photon-mediated spin interactions demonstrated here may be engineered to create dynamical gauge fields and quantum spin glasses.
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Affiliation(s)
- Ronen M Kroeze
- Department of Physics, Stanford University, Stanford, California 94305, USA
- E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA
| | - Yudan Guo
- Department of Physics, Stanford University, Stanford, California 94305, USA
- E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA
| | - Varun D Vaidya
- Department of Physics, Stanford University, Stanford, California 94305, USA
- E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Jonathan Keeling
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS United Kingdom
| | - Benjamin L Lev
- Department of Physics, Stanford University, Stanford, California 94305, USA
- E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
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7
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Luo XW, Zhang C. Self-Adapted Floquet Dynamics of Ultracold Bosons in a Cavity. PHYSICAL REVIEW LETTERS 2018; 120:263202. [PMID: 30004716 DOI: 10.1103/physrevlett.120.263202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 05/04/2018] [Indexed: 06/08/2023]
Abstract
Floquet dynamics of a quantum system subject to periodic modulations of system parameters provides a powerful tool for engineering new quantum matter with exotic properties. While system dynamics is significantly altered, the periodic modulation itself is usually induced externally and independent of Floquet dynamics. Here we propose a new type of Floquet physics for a Bose-Einstein condensate (BEC) subject to a shaken lattice generated inside a cavity, where the shaken lattice and atomic Floquet bands are mutually dependent, resulting in self-adapted Floquet dynamics. In particular, the shaken lattice induces Floquet quasienergy bands for the BEC, whose backaction leads to a self-adapted dynamical normal-superradiant phase transition for the shaken lattice. Such self-adapted Floquet dynamics shows two surprising and unique features: (i) The normal-superradiant phase transition possesses a hysteresis even without atom interactions. (ii) The dynamical atom-cavity steady state could exist at free energy maxima. The atom interactions strongly affect the phase transition of the BEC from zero to finite momenta. Our results provide a powerful platform for exploring self-adapted Floquet physics, which may open an avenue for engineering novel quantum materials.
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Affiliation(s)
- Xi-Wang Luo
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
| | - Chuanwei Zhang
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
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8
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Quantum State Reduction by Matter-Phase-Related Measurements in Optical Lattices. Sci Rep 2017; 7:42597. [PMID: 28225012 PMCID: PMC5320499 DOI: 10.1038/srep42597] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 01/11/2017] [Indexed: 11/20/2022] Open
Abstract
A many-body atomic system coupled to quantized light is subject to weak measurement. Instead of coupling light to the on-site density, we consider the quantum backaction due to the measurement of matter-phase-related variables such as global phase coherence. We show how this unconventional approach opens up new opportunities to affect system evolution. We demonstrate how this can lead to a new class of final states different from those possible with dissipative state preparation or conventional projective measurements. These states are characterised by a combination of Hamiltonian and measurement properties thus extending the measurement postulate for the case of strong competition with the system’s own evolution.
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9
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Mivehvar F, Ritsch H, Piazza F. Superradiant Topological Peierls Insulator inside an Optical Cavity. PHYSICAL REVIEW LETTERS 2017; 118:073602. [PMID: 28256867 DOI: 10.1103/physrevlett.118.073602] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Indexed: 06/06/2023]
Abstract
We consider a spinless ultracold Fermi gas tightly trapped along the axis of an optical resonator and transversely illuminated by a laser closely tuned to a resonator mode. At a certain threshold pump intensity, the homogeneous gas density breaks a Z_{2} symmetry towards a spatially periodic order, which collectively scatters pump photons into the cavity. We show that this known self-ordering transition also occurs for low field seeking fermionic particles when the laser light is blue detuned to an atomic transition. The emergent superradiant optical lattice in this case is homopolar and possesses two distinct dimerizations. Depending on the spontaneously chosen dimerization, the resulting Bloch bands can have a nontrivial topological structure characterized by a nonvanishing Zak phase. In the case where the Fermi momentum is close to half of the cavity-mode wave number, a Peierls-like instability here creates a topological insulator with a gap at the Fermi surface, which hosts a pair of edge states. The topological features of the system can be nondestructively observed via the cavity output: the Zak phase of the bulk coincides with the relative phase between laser and cavity field, while the fingerprint of edge states can be observed as additional broadening in a well-defined frequency window of the cavity spectrum.
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Affiliation(s)
- Farokh Mivehvar
- Institut für Theoretische Physik, Universität Innsbruck, A-6020 Innsbruck, Austria
| | - Helmut Ritsch
- Institut für Theoretische Physik, Universität Innsbruck, A-6020 Innsbruck, Austria
| | - Francesco Piazza
- Institut für Theoretische Physik, Universität Innsbruck, A-6020 Innsbruck, Austria
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10
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Su SW, Lu ZK, Gou SC, Liao WT. Controllable vacuum-induced diffraction of matter-wave superradiance using an all-optical dispersive cavity. Sci Rep 2016; 6:35402. [PMID: 27748413 PMCID: PMC5066314 DOI: 10.1038/srep35402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 09/28/2016] [Indexed: 11/09/2022] Open
Abstract
Cavity quantum electrodynamics (CQED) has played a central role in demonstrating the fundamental principles of the quantum world, and in particular those of atom-light interactions. Developing fast, dynamical and non-mechanical control over a CQED system is particularly desirable for controlling atomic dynamics and building future quantum networks at high speed. However conventional mirrors do not allow for such flexible and fast controls over their coupling to intracavity atoms mediated by photons. Here we theoretically investigate a novel all-optical CQED system composed of a binary Bose-Einstein condensate (BEC) sandwiched by two atomic ensembles. The highly tunable atomic dispersion of the CQED system enables the medium to act as a versatile, all-optically controlled atomic mirror that can be employed to manipulate the vacuum-induced diffraction of matter-wave superradiance. Our study illustrates a innovative all-optical element of atomtroics and sheds new light on controlling light-matter interactions.
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Affiliation(s)
- Shih-Wei Su
- Department of Physics and Graduate Institute of Photonics, National Changhua University of Education, Changhua 50058, Taiwan
| | - Zhen-Kai Lu
- Max Planck Institute for Quantum Optics, D-85748 Garching, Germany
| | - Shih-Chuan Gou
- Department of Physics and Graduate Institute of Photonics, National Changhua University of Education, Changhua 50058, Taiwan
| | - Wen-Te Liao
- Department of Physics, National Central University, 32001 Taoyuan City, Taiwan.,Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany.,Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany.,Center for Free-Electron Laser Science, 22761 Hamburg, Germany
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11
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Quantum measurement-induced antiferromagnetic order and density modulations in ultracold Fermi gases in optical lattices. Sci Rep 2016; 6:31196. [PMID: 27510369 PMCID: PMC4980619 DOI: 10.1038/srep31196] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 07/14/2016] [Indexed: 11/16/2022] Open
Abstract
Ultracold atomic systems offer a unique tool for understanding behavior of matter in the quantum degenerate regime, promising studies of a vast range of phenomena covering many disciplines from condensed matter to quantum information and particle physics. Coupling these systems to quantized light fields opens further possibilities of observing delicate effects typical of quantum optics in the context of strongly correlated systems. Measurement backaction is one of the most funda- mental manifestations of quantum mechanics and it is at the core of many famous quantum optics experiments. Here we show that quantum backaction of weak measurement can be used for tailoring long-range correlations of ultracold fermions, realizing quantum states with spatial modulations of the density and magnetization, thus overcoming usual requirement for a strong interatomic interactions. We propose detection schemes for implementing antiferromagnetic states and density waves. We demonstrate that such long-range correlations cannot be realized with local addressing, and they are a consequence of the competition between global but spatially structured backaction of weak quantum measurement and unitary dynamics of fermions.
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12
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Nefedkin NE, Andrianov ES, Zyablovsky AA, Pukhov AA, Dorofeenko AV, Vinogradov AP, Lisyansky AA. Superradiance of a subwavelength array of classical nonlinear emitters. OPTICS EXPRESS 2016; 24:3464-78. [PMID: 26907005 DOI: 10.1364/oe.24.003464] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We suggest a mechanism by which a superradiant burst emerges from a subwavelength array of nonlinear classical emitters that are not initially synchronized. The emitters interact via the field of their common radiative response. We show that only if the distribution of initial phases is not uniform does a non-zero field of radiative response arise, leading to a superradiant burst. Although this field cannot synchronize the emitters, it engenders long period envelopes for their fast oscillations. Constructive interference in the envelopes of several emitters creates a large fluctuation in dipole moments that results in a superradiant pulse. The intensity of this pulse is proportional to the square of the number of emitters participating in the fluctuation.
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13
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Klinder J, Keßler H, Bakhtiari MR, Thorwart M, Hemmerich A. Observation of a Superradiant Mott Insulator in the Dicke-Hubbard Model. PHYSICAL REVIEW LETTERS 2015; 115:230403. [PMID: 26684102 DOI: 10.1103/physrevlett.115.230403] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Indexed: 06/05/2023]
Abstract
It is well known that the bosonic Hubbard model possesses a Mott insulator phase. Likewise, it is known that the Dicke model exhibits a self-organized superradiant phase. By implementing an optical lattice inside of a high-finesse optical cavity, both models are merged such that an extended Hubbard model with cavity-mediated infinite range interactions arises. In addition to a normal superfluid phase, two superradiant phases are found, one of them coherent and hence superfluid and one incoherent Mott insulating.
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Affiliation(s)
- J Klinder
- Institut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - H Keßler
- Institut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - M Reza Bakhtiari
- I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany
| | - M Thorwart
- I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany
| | - A Hemmerich
- Institut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
- Wilczek Quantum Center, Zhejiang University of Technology, Hangzhou 310023, China
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14
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Two-Photon Collective Atomic Recoil Lasing. ATOMS 2015. [DOI: 10.3390/atoms3040495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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15
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Piazza F, Ritsch H. Self-Ordered Limit Cycles, Chaos, and Phase Slippage with a Superfluid inside an Optical Resonator. PHYSICAL REVIEW LETTERS 2015; 115:163601. [PMID: 26550874 DOI: 10.1103/physrevlett.115.163601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Indexed: 06/05/2023]
Abstract
We study dynamical phases of a driven Bose-Einstein condensate coupled to the light field of a high-Q optical cavity. For high field seeking atoms at red detuning the system is known to show a transition from a spatially homogeneous steady state to a self-ordered regular lattice exhibiting superradiant scattering into the cavity. For blue atom pump detuning the particles are repelled from the maxima of the light-induced optical potential suppressing scattering. We show that this generates a new dynamical instability of the self-ordered phase, leading to the appearance of self-ordered stable limit cycles characterized by large amplitude self-sustained oscillations of both the condensate density and cavity field. The limit cycles evolve into chaotic behavior by period doubling. Large amplitude oscillations of the condensate are accompanied by phase slippage through soliton nucleation at a rate that increases in the chaotic regime. Different from a superfluid in a closed setup, this driven dissipative superfluid is not destroyed by the proliferation of solitons since kinetic energy is removed through cavity losses.
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Affiliation(s)
- Francesco Piazza
- Institut für Theoretische Physik, Universität Innsbruck, A-6020 Innsbruck, Austria
| | - Helmut Ritsch
- Institut für Theoretische Physik, Universität Innsbruck, A-6020 Innsbruck, Austria
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16
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17
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18
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Nagy D, Domokos P. Nonequilibrium Quantum Criticality and Non-Markovian Environment: Critical Exponent of a Quantum Phase Transition. PHYSICAL REVIEW LETTERS 2015; 115:043601. [PMID: 26252683 DOI: 10.1103/physrevlett.115.043601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Indexed: 06/04/2023]
Abstract
We show that the critical exponent of a quantum phase transition in a damped-driven open system is determined by the spectral density function of the reservoir. We consider the open-system variant of the Dicke model, where the driven boson mode and also the large N spin couple to independent reservoirs at zero temperature. The critical exponent, which is 1 if there is no spin-bath coupling, decreases below 1 when the spin couples to a sub-Ohmic reservoir.
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Affiliation(s)
- D Nagy
- Institute for Solid State Physics and Optics, Wigner Research Centre, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary
| | - P Domokos
- Institute for Solid State Physics and Optics, Wigner Research Centre, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary
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19
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Robb GRM, Tesio E, Oppo GL, Firth WJ, Ackemann T, Bonifacio R. Quantum threshold for optomechanical self-structuring in a Bose-Einstein condensate. PHYSICAL REVIEW LETTERS 2015; 114:173903. [PMID: 25978236 DOI: 10.1103/physrevlett.114.173903] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Indexed: 06/04/2023]
Abstract
Theoretical analysis of the optomechanics of degenerate bosonic atoms with a single feedback mirror shows that self-structuring occurs only above an input threshold that is quantum mechanical in origin. This threshold also implies a lower limit to the size (period) of patterns that can be produced in a condensate for a given pump intensity. These thresholds are interpreted as due to the quantum rigidity of Bose-Einstein condensates, which has no classical counterpart. Above the threshold, the condensate self-organizes into an ordered supersolid state with a spatial period self-selected by optical diffraction.
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Affiliation(s)
- G R M Robb
- SUPA and Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, United Kingdom
| | - E Tesio
- SUPA and Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, United Kingdom
| | - G-L Oppo
- SUPA and Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, United Kingdom
| | - W J Firth
- SUPA and Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, United Kingdom
| | - T Ackemann
- SUPA and Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, United Kingdom
| | - R Bonifacio
- INFN-LNF, Via Enrico Fermi, 40-00044 Frascati, Rome, Italy
- SUPA and Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, United Kingdom
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20
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Bakhtiari MR, Hemmerich A, Ritsch H, Thorwart M. Nonequilibrium phase transition of interacting bosons in an intra-cavity optical lattice. PHYSICAL REVIEW LETTERS 2015; 114:123601. [PMID: 25860742 DOI: 10.1103/physrevlett.114.123601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Indexed: 06/04/2023]
Abstract
We investigate the nonlinear light-matter interaction of a Bose-Einstein condensate trapped in an external periodic potential inside an optical cavity which is weakly coupled to vacuum radiation modes and driven by a transverse pump field. Based on a generalized Bose-Hubbard model which incorporates a single cavity mode, we include the collective backaction of the atoms on the cavity light field and determine the nonequilibrium quantum phases within the nonperturbative bosonic dynamical mean-field theory. With the system parameters adapted to recent experiments, we find a quantum phase transition from a normal phase to a self-organized superfluid phase, which is related to the Hepp-Lieb-Dicke superradiance phase transition. For even stronger pumping, a self-organized Mott insulator phase arises.
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Affiliation(s)
- M Reza Bakhtiari
- I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany
| | - A Hemmerich
- Institut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - H Ritsch
- Institute for Theoretical Physics, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - M Thorwart
- I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany
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21
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Abstract
The Dicke model with a weak dissipation channel is realized by coupling a Bose-Einstein condensate to an optical cavity with ultranarrow bandwidth. We explore the dynamical critical properties of the Hepp-Lieb-Dicke phase transition by performing quenches across the phase boundary. We observe hysteresis in the transition between a homogeneous phase and a self-organized collective phase with an enclosed loop area showing power-law scaling with respect to the quench time, which suggests an interpretation within a general framework introduced by Kibble and Zurek. The observed hysteretic dynamics is well reproduced by numerically solving the mean-field equation derived from a generalized Dicke Hamiltonian. Our work promotes the understanding of nonequilibrium physics in open many-body systems with infinite range interactions.
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Reimann R, Alt W, Kampschulte T, Macha T, Ratschbacher L, Thau N, Yoon S, Meschede D. Cavity-modified collective Rayleigh scattering of two atoms. PHYSICAL REVIEW LETTERS 2015; 114:023601. [PMID: 25635545 DOI: 10.1103/physrevlett.114.023601] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Indexed: 06/04/2023]
Abstract
We report on the observation of cooperative radiation of exactly two neutral atoms strongly coupled to the single mode field of an optical cavity, which is close to the lossless-cavity limit. Monitoring the cavity output power, we observe constructive and destructive interference of collective Rayleigh scattering for certain relative distances between the two atoms. Because of cavity backaction onto the atoms, the cavity output power for the constructive two-atom case (N=2) is almost equal to the single-emitter case (N=1), which is in contrast to free-space where one would expect an N^{2} scaling of the power. These effects are quantitatively explained by a classical model as well as by a quantum mechanical model based on Dicke states. We extract information on the relative phases of the light fields at the atom positions and employ advanced cooling to reduce the jump rate between the constructive and destructive atom configurations. Thereby we improve the control over the system to a level where the implementation of two-atom entanglement schemes involving optical cavities becomes realistic.
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Affiliation(s)
- René Reimann
- Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - Wolfgang Alt
- Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - Tobias Kampschulte
- Departement Physik, Universität Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Tobias Macha
- Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - Lothar Ratschbacher
- Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - Natalie Thau
- Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - Seokchan Yoon
- Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany
| | - Dieter Meschede
- Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany
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