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Gawryluk K, Brewczyk M. Mechanism for sound dissipation in a two-dimensional degenerate Fermi gas. Sci Rep 2024; 14:10815. [PMID: 38734745 PMCID: PMC11088693 DOI: 10.1038/s41598-024-61521-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 05/07/2024] [Indexed: 05/13/2024] Open
Abstract
We numerically study the transport properties of a two-dimensional Fermi gas in a weakly and strongly interacting regimes, in the range of temperatures close to the transition to a superfluid phase. For that we excite sound waves in a fermionic mixture by using the phase imprinting technique, follow their evolution, and finally determine both their speed and attenuation. Our formalism, originated from a density-functional theory, incorporates thermal fluctuations via the grand canonical ensemble description and with the help of Metropolis algoritm. From numerical simulations we extract temperature dependence of the sound velocity and diffusivity as well as the dependence on the interaction strength. We emphasize the role of virtual vortex-antivortex pairs creation in the process of sound dissipation.
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Affiliation(s)
- Krzysztof Gawryluk
- Wydział Fizyki, Uniwersytet w Białymstoku, ul. K. Ciołkowskiego 1L, 15245, Białystok, Poland.
| | - Mirosław Brewczyk
- Wydział Fizyki, Uniwersytet w Białymstoku, ul. K. Ciołkowskiego 1L, 15245, Białystok, Poland
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2
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First and Second Sound in Two-Dimensional Bosonic and Fermionic Superfluids. Symmetry (Basel) 2022. [DOI: 10.3390/sym14102182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We review our theoretical results of the sound propagation in two-dimensional (2D) systems of ultracold fermionic and bosonic atoms. In the superfluid phase, characterized by the spontaneous symmetry breaking of the U(1) symmetry, there is the coexistence of first and second sound. In the case of weakly-interacting repulsive bosons, we model the recent measurements of the sound velocities of 39K atoms in 2D obtained in the weakly-interacting regime and around the Berezinskii–Kosterlitz–Thouless (BKT) superfluid-to-normal transition temperature. In particular, we perform a quite accurate computation of the superfluid density and show that it is reasonably consistent with the experimental results. For superfluid attractive fermions, we calculate the first and second sound velocities across the whole BCS-BEC crossover. In the low-temperature regime, we reproduce the recent measurements of first-sound speed with 6Li atoms. We also predict that there is mixing between sound modes only in the finite-temperature BEC regime.
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Bland T, Poli E, Politi C, Klaus L, Norcia MA, Ferlaino F, Santos L, Bisset RN. Two-Dimensional Supersolid Formation in Dipolar Condensates. PHYSICAL REVIEW LETTERS 2022; 128:195302. [PMID: 35622047 DOI: 10.1103/physrevlett.128.195302] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 01/19/2022] [Accepted: 04/11/2022] [Indexed: 06/15/2023]
Abstract
Dipolar condensates have recently been coaxed to form the long-sought supersolid phase. While one-dimensional supersolids may be prepared by triggering a roton instability, we find that such a procedure in two dimensions (2D) leads to a loss of both global phase coherence and crystalline order. Unlike in 1D, the 2D roton modes have little in common with the supersolid configuration. We develop a finite-temperature stochastic Gross-Pitaevskii theory that includes beyond-mean-field effects to explore the formation process in 2D and find that evaporative cooling directly into the supersolid phase-hence bypassing the first-order roton instability-can produce a robust supersolid in a circular trap. Importantly, the resulting supersolid is stable at the final nonzero temperature. We then experimentally produce a 2D supersolid in a near-circular trap through such an evaporative procedure. Our work provides insight into the process of supersolid formation in 2D and defines a realistic path to the formation of large two-dimensional supersolid arrays.
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Affiliation(s)
- T Bland
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Innsbruck 6020, Austria
| | - E Poli
- Institut für Experimentalphysik, Universität Innsbruck, Innsbruck 6020, Austria
| | - C Politi
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Innsbruck 6020, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Innsbruck 6020, Austria
| | - L Klaus
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Innsbruck 6020, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Innsbruck 6020, Austria
| | - M A Norcia
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Innsbruck 6020, Austria
| | - F Ferlaino
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Innsbruck 6020, Austria
- Institut für Experimentalphysik, Universität Innsbruck, Innsbruck 6020, Austria
| | - L Santos
- Institut für Theoretische Physik, Leibniz Universität Hannover, Hannover 30167, Germany
| | - R N Bisset
- Institut für Experimentalphysik, Universität Innsbruck, Innsbruck 6020, Austria
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4
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Christodoulou P, Gałka M, Dogra N, Lopes R, Schmitt J, Hadzibabic Z. Observation of first and second sound in a BKT superfluid. Nature 2021; 594:191-194. [PMID: 34108696 DOI: 10.1038/s41586-021-03537-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 04/12/2021] [Indexed: 02/05/2023]
Abstract
Superfluidity in its various forms has been of interest since the observation of frictionless flow in liquid helium II1,2. In three spatial dimensions it is conceptually associated with the emergence of long-range order at a critical temperature. One of the hallmarks of superfluidity, as predicted by the two-fluid model3,4 and observed in both liquid helium5 and in ultracold atomic gases6,7, is the existence of two kinds of sound excitation-the first and second sound. In two-dimensional systems, thermal fluctuations preclude long-range order8,9; however, superfluidity nevertheless emerges at a non-zero critical temperature through the infinite-order Berezinskii-Kosterlitz-Thouless (BKT) transition10,11, which is associated with a universal jump12 in the superfluid density without any discontinuities in the thermodynamic properties of the fluid. BKT superfluids are also predicted to support two sounds, but so far this has not been observed experimentally. Here we observe first and second sound in a homogeneous two-dimensional atomic Bose gas, and use the two temperature-dependent sound speeds to determine the superfluid density of the gas13-16. Our results agree with the predictions of BKT theory, including the prediction of a universal jump in the superfluid density at the critical temperature.
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Affiliation(s)
| | - Maciej Gałka
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Nishant Dogra
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Raphael Lopes
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, Sorbonne Université, Paris, France
| | - Julian Schmitt
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.,Institut für Angewandte Physik, Universität Bonn, Bonn, Germany
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Berezinskii-Kosterlitz-Thouless phase induced by dissipating quasisolitons. Sci Rep 2021; 11:10773. [PMID: 34031458 PMCID: PMC8144421 DOI: 10.1038/s41598-021-90169-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 05/05/2021] [Indexed: 11/08/2022] Open
Abstract
We theoretically study the sound propagation in a two-dimensional weakly interacting uniform Bose gas. Using the classical fields approximation we analyze in detail the properties of density waves generated both in a weak and strong perturbation regimes. While in the former case density excitations can be described in terms of hydrodynamic or collisionless sound, the strong disturbance of the system results in a qualitatively different response. We identify observed structures as quasisolitons and uncover their internal complexity for strong perturbation case. For this regime quasisolitons break into vortex pairs as time progresses, eventually reaching an equilibrium state. We find this state, characterized by only fluctuating in time averaged number of pairs of opposite charge vortices and by appearance of a quasi-long-range order, as the Berezinskii-Kosterlitz-Thouless (BKT) phase.
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6
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Estrecho E, Pieczarka M, Wurdack M, Steger M, West K, Pfeiffer LN, Snoke DW, Truscott AG, Ostrovskaya EA. Low-Energy Collective Oscillations and Bogoliubov Sound in an Exciton-Polariton Condensate. PHYSICAL REVIEW LETTERS 2021; 126:075301. [PMID: 33666453 DOI: 10.1103/physrevlett.126.075301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 08/24/2020] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
We report the observation of low-energy, low-momenta collective oscillations of an exciton-polariton condensate in a round "box" trap. The oscillations are dominated by the dipole and breathing modes, and the ratio of the frequencies of the two modes is consistent with that of a weakly interacting two-dimensional trapped Bose gas. The speed of sound extracted from the dipole oscillation frequency is smaller than the Bogoliubov sound, which can be partly explained by the influence of the incoherent reservoir. These results pave the way for understanding the effects of reservoir, dissipation, energy relaxation, and finite temperature on the superfluid properties of exciton-polariton condensates and other two-dimensional open-dissipative quantum fluids.
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Affiliation(s)
- E Estrecho
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies & Nonlinear Physics Centre, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - M Pieczarka
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies & Nonlinear Physics Centre, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - M Wurdack
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies & Nonlinear Physics Centre, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - M Steger
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - K West
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - L N Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - D W Snoke
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - A G Truscott
- Laser Physics Centre, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - E A Ostrovskaya
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies & Nonlinear Physics Centre, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
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7
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Ville JL, Saint-Jalm R, Le Cerf É, Aidelsburger M, Nascimbène S, Dalibard J, Beugnon J. Sound Propagation in a Uniform Superfluid Two-Dimensional Bose Gas. PHYSICAL REVIEW LETTERS 2018; 121:145301. [PMID: 30339451 DOI: 10.1103/physrevlett.121.145301] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Indexed: 06/08/2023]
Abstract
In superfluid systems several sound modes can be excited, such as, for example, first and second sound in liquid helium. Here, we excite running and standing waves in a uniform two-dimensional Bose gas and we characterize the propagation of sound in both the superfluid and normal regimes. In the superfluid phase, the measured speed of sound is in good agreement with the prediction of a two-fluid hydrodynamic model, and the weak damping is well explained by the scattering with thermal excitations. In the normal phase we observe a stronger damping, which we attribute to a departure from hydrodynamic behavior.
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Affiliation(s)
- J L Ville
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France
| | - R Saint-Jalm
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France
| | - É Le Cerf
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France
| | - M Aidelsburger
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France
| | - S Nascimbène
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France
| | - J Dalibard
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France
| | - J Beugnon
- Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France
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