1
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Wang L, Yan X, Min J, Sun D, Xie X, Peng SG, Zhan M, Jiang K. Scale Invariance of a Spherical Unitary Fermi Gas. PHYSICAL REVIEW LETTERS 2024; 132:243403. [PMID: 38949354 DOI: 10.1103/physrevlett.132.243403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 04/06/2024] [Accepted: 05/21/2024] [Indexed: 07/02/2024]
Abstract
A unitary Fermi gas in an isotropic harmonic trap is predicted to show scale and conformal symmetry that have important consequences in its thermodynamic and dynamical properties. By experimentally realizing a unitary Fermi gas in an isotropic harmonic trap, we demonstrate its universal expansion dynamics along each direction and at different temperatures. We show that as a consequence of SO(2,1) symmetry, the measured release energy is equal to that of the trapping energy. We further observe the breathing mode with an oscillation frequency twice the trapping frequency and a small damping rate, providing the evidence of SO(2,1) symmetry. In addition, away from resonance when scale invariance is broken, we determine the effective exponent γ that relates the chemical potential and average density along the BEC-BCS crossover, which qualitatively agrees with the mean field predictions. This Letter opens the possibility of studying nonequilibrium dynamics in a conformal invariant system in the future.
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Affiliation(s)
| | - Xiangchuan Yan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | | | - Dali Sun
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | | | - Shi-Guo Peng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Mingsheng Zhan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Kaijun Jiang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
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2
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Wang Y, Du H, Li Y, Mei F, Hu Y, Xiao L, Ma J, Jia S. Testing universality of Feynman-Tan relation in interacting Bose gases using high-order Bragg spectra. LIGHT, SCIENCE & APPLICATIONS 2023; 12:50. [PMID: 36854664 PMCID: PMC9975228 DOI: 10.1038/s41377-023-01103-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 02/06/2023] [Accepted: 02/13/2023] [Indexed: 06/18/2023]
Abstract
The Feynman-Tan relation, obtained by combining the Feynman energy relation with the Tan's two-body contact, can explain the excitation spectra of strongly interacting 39K Bose-Einstein condensate (BEC). Since the shift of excitation resonance in the Feynman-Tan relation is inversely proportional to atomic mass, the test of whether this relation is universal for other atomic systems is significant for describing the effect of interaction in strongly correlated Bose gases. Here we measure the high-momentum excitation spectra of 133Cs BEC with widely tunable interactions by using the second- and third-order Bragg spectra. We observe the backbending of frequency shift of excitation resonance with increasing interaction, and even the shift changes its sign under the strong interactions in the high-order Bragg spectra. Our finding shows good agreement with the prediction based on the Feynman-Tan relation. Our results provide significant insights for understanding the profound properties of strongly interacting Bose gases.
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Affiliation(s)
- Yunfei Wang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China
| | - Huiying Du
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China
| | - Yuqing Li
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China.
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China.
| | - Feng Mei
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China
| | - Ying Hu
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China
| | - Liantuan Xiao
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China
| | - Jie Ma
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China.
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China.
- Hefei National Laboratory, Hefei, China.
| | - Suotang Jia
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China
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3
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Maki J, Zhang S, Zhou F. Dynamics of Strongly Interacting Fermi Gases with Time-Dependent Interactions: Consequence of Conformal Symmetry. PHYSICAL REVIEW LETTERS 2022; 128:040401. [PMID: 35148156 DOI: 10.1103/physrevlett.128.040401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 12/24/2021] [Indexed: 06/14/2023]
Abstract
In this Letter, we investigate the effects of a time-dependent, short-ranged interaction on the long-time expansion dynamics of Fermi gases. We show that the effects of the interaction on the dynamics is dictated by how it changes under a conformal transformation, and derive an explicit criterion for the relevancy of time-dependent interactions near both the strongly and noninteracting scale invariant limits. In addition, we show that it is possible to engineer interactions that give rise to nonexponential thermalization dynamics in trapped Fermi gases. To supplement the symmetry analysis, we perform hydrodynamic simulations to show that the moment of inertia of the trapped gas indeed follows a universal time dependence that is determined jointly by the conformal symmetry and time-dependent scattering length a(t). Our results should also be relevant to the dynamics of other systems that are nearly scale invariant and that are governed by a nonrelativistic conformal symmetry.
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Affiliation(s)
- Jeff Maki
- Department of Physics and HKU-UCAS Joint Institute for Theoretical and Computational Physics at Hong Kong, Guangdong-Hong Kong Joint Laboratory of Quantum Matter, The University of Hong Kong, Hong Kong, China
| | - Shizhong Zhang
- Department of Physics and HKU-UCAS Joint Institute for Theoretical and Computational Physics at Hong Kong, Guangdong-Hong Kong Joint Laboratory of Quantum Matter, The University of Hong Kong, Hong Kong, China
| | - Fei Zhou
- Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada
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4
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Zhang X, Chen Y, Wu Z, Wang J, Fan J, Deng S, Wu H. Observation of a superradiant quantum phase transition in an intracavity degenerate Fermi gas. Science 2021; 373:1359-1362. [PMID: 34446446 DOI: 10.1126/science.abd4385] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Xiaotian Zhang
- State Key Laboratory of Precision Spectroscopy, School of Physics and Electronics Science, East China Normal University, Shanghai 200062, P. R. China
| | - Yu Chen
- Graduate School of China Academy of Engineering Physics, Beijing 100193, P. R. China
| | - Zemao Wu
- State Key Laboratory of Precision Spectroscopy, School of Physics and Electronics Science, East China Normal University, Shanghai 200062, P. R. China
| | - Juan Wang
- State Key Laboratory of Precision Spectroscopy, School of Physics and Electronics Science, East China Normal University, Shanghai 200062, P. R. China
| | - Jijie Fan
- State Key Laboratory of Precision Spectroscopy, School of Physics and Electronics Science, East China Normal University, Shanghai 200062, P. R. China
| | - Shujin Deng
- State Key Laboratory of Precision Spectroscopy, School of Physics and Electronics Science, East China Normal University, Shanghai 200062, P. R. China
| | - Haibin Wu
- State Key Laboratory of Precision Spectroscopy, School of Physics and Electronics Science, East China Normal University, Shanghai 200062, P. R. China.,NYU-ECNU Institute of Physics at NYU Shanghai, Shanghai 200062, P. R. China.,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, P. R. China
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5
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Qi R, Shi Z, Zhai H. Maximum Energy Growth Rate in Dilute Quantum Gases. PHYSICAL REVIEW LETTERS 2021; 126:240401. [PMID: 34213925 DOI: 10.1103/physrevlett.126.240401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/19/2021] [Accepted: 05/21/2021] [Indexed: 06/13/2023]
Abstract
In this Letter we study how fast the energy density of a quantum gas can increase in time, when the interatomic interaction characterized by the s-wave scattering length a_{s} is increased from zero with arbitrary time dependence. We show that, at short time, the energy density can at most increase as sqrt[t], which can be achieved when the time dependence of a_{s} is also proportional to sqrt[t], and especially, a universal maximum energy growth rate can be reached when a_{s} varies as 2sqrt[ℏt/(πm)]. If a_{s} varies faster or slower than sqrt[t], it is, respectively, proximate to the quench process and the adiabatic process, and both result in a slower energy growth rate. These results are obtained by analyzing the short time dynamics of the short-range behavior of the many-body wave function characterized by the contact, and are also confirmed by numerically solving an example of interacting bosons with time-dependent Bogoliubov theory. These results can also be verified experimentally in ultracold atomic gases.
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Affiliation(s)
- Ran Qi
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Zheyu Shi
- Key State Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Hui Zhai
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
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6
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Del Campo A. Probing Quantum Speed Limits with Ultracold Gases. PHYSICAL REVIEW LETTERS 2021; 126:180603. [PMID: 34018797 DOI: 10.1103/physrevlett.126.180603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Accepted: 03/31/2021] [Indexed: 06/12/2023]
Abstract
Quantum speed limits (QSLs) rule the minimum time for a quantum state to evolve into a distinguishable state in an arbitrary physical process. These fundamental results constrain a notion of distance traveled by the quantum state, known as the Bures angle, in terms of the speed of evolution set by nonadiabatic energy fluctuations. I theoretically propose how to measure QSLs in an ultracold quantum gas confined in a time-dependent harmonic trap. In this highly-dimensional system of continuous variables, quantum tomography is prohibited. Yet, QSLs can be probed whenever the dynamics is self-similar by measuring as a function of time the cloud size of the ultracold gas. This makes it possible to determine the Bures angle and energy fluctuations, as I discuss for various ultracold atomic systems.
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Affiliation(s)
- Adolfo Del Campo
- Department of Physics and Materials Science, University of Luxembourg, L-1511 Luxembourg, Luxembourg; Donostia International Physics Center, E-20018 San Sebastián, Spain; IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain; Department of Physics, University of Massachusetts, Boston, Massachusetts 02125, USA and Theory Division, Los Alamos National Laboratory, MS-B213, Los Alamos, New Mexico 87545, USA
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7
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Wang Y, Li Y, Wu J, Liu W, Hu J, Ma J, Xiao L, Jia S. Hybrid evaporative cooling of 133Cs atoms to Bose-Einstein condensation. OPTICS EXPRESS 2021; 29:13960-13967. [PMID: 33985122 DOI: 10.1364/oe.419854] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 04/14/2021] [Indexed: 06/12/2023]
Abstract
The Bose-Einstein condensation (BEC) of 133Cs atoms offers an appealing platform for studying the many-body physics of interacting Bose quantum gases, owing to the rich Feshbach resonances that can be readily achieved in the low magnetic field region. However, it is notoriously difficult to cool 133Cs atoms to their quantum degeneracy. Here we report a hybrid evaporative cooling of 133Cs atoms to BEC. Our approach relies on a combination of the magnetically tunable evaporation with the optical evaporation of atoms in a magnetically levitated optical dipole trap overlapping with a dimple trap. The magnetic field gradient is reduced for the magnetically tunable evaporation. The subsequent optical evaporation is performed by lowering the depth of the dimple trap. We study the dependence of the peak phase space density (PSD) and temperature on the number of atoms during the evaporation process, as well as how the PSD and atom number vary with the trap depth. The results are in excellent agreement with the equation model for evaporative cooling.
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8
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Lv C, Zhang R, Zhou Q. SU(1,1) Echoes for Breathers in Quantum Gases. PHYSICAL REVIEW LETTERS 2020; 125:253002. [PMID: 33416377 DOI: 10.1103/physrevlett.125.253002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 11/16/2020] [Indexed: 06/12/2023]
Abstract
Though the celebrated spin echoes have been widely used to reverse quantum dynamics, they are not applicable to systems whose constituents are beyond the control of the su(2) algebra. Here, we design echoes to reverse quantum dynamics of breathers in three-dimensional unitary fermions and two-dimensional bosons and fermions with contact interactions, which are governed by an underlying su(1,1) algebra. Geometrically, SU(1,1) echoes produce closed trajectories on a single or multiple Poincaré disks and thus could recover any initial states without changing the sign of the Hamiltonian. In particular, the initial shape of a breather determines the superposition of trajectories on multiple Poincaré disks and whether the revival time has period multiplication. Our work provides physicists with a recipe to tailor collective excitations of interacting many-body systems.
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Affiliation(s)
- Chenwei Lv
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Ren Zhang
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- School of Science, Xi'an Jiaotong University, Xi'an, Shaanxi 710049
| | - Qi Zhou
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, Indiana 47907, USA
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9
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Lyu C, Lv C, Zhou Q. Geometrizing Quantum Dynamics of a Bose-Einstein Condensate. PHYSICAL REVIEW LETTERS 2020; 125:253401. [PMID: 33416381 DOI: 10.1103/physrevlett.125.253401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 11/12/2020] [Indexed: 06/12/2023]
Abstract
We show that quantum dynamics of Bose-Einstein condensates in the weakly interacting regime can be geometrized by a Poincaré disk. Each point on such a disk represents a thermofield double state, the overlap between which equals the metric of this hyperbolic space. This approach leads to a unique geometric interpretation of stable and unstable modes as closed and open trajectories on the Poincaré disk, respectively. The resonant modes that follow geodesics naturally equate fundamental quantities including the time, the length, and the temperature. Our work suggests a new geometric framework to coherently control quantum systems and reverse their dynamics using SU(1,1) echoes. In the presence of perturbations breaking the SU(1,1) symmetry, SU(1,1) echoes deliver a new means to measure these perturbations such as the interactions between excited particles.
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Affiliation(s)
- Changyuan Lyu
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Chenwei Lv
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Qi Zhou
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, Indiana 47907, USA
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10
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Nonadiabatic Energy Fluctuations of Scale-Invariant Quantum Systems in a Time-Dependent Trap. ENTROPY 2020; 22:e22050515. [PMID: 33286287 PMCID: PMC7517006 DOI: 10.3390/e22050515] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 04/28/2020] [Accepted: 04/29/2020] [Indexed: 11/16/2022]
Abstract
We consider the nonadiabatic energy fluctuations of a many-body system in a time-dependent harmonic trap. In the presence of scale-invariance, the dynamics becomes self-similar and the nondiabatic energy fluctuations can be found in terms of the initial expectation values of the second moments of the Hamiltonian, square position, and squeezing operators. Nonadiabatic features are expressed in terms of the scaling factor governing the size of the atomic cloud, which can be extracted from time-of-flight images. We apply this exact relation to a number of examples: the single-particle harmonic oscillator, the one-dimensional Calogero-Sutherland model, describing bosons with inverse-square interactions that includes the non-interacting Bose gas and the Tonks-Girdardeau gas as limiting cases, and the unitary Fermi gas. We illustrate these results for various expansion protocols involving sudden quenches of the trap frequency, linear ramps and shortcuts to adiabaticity. Our results pave the way to the experimental study of nonadiabatic energy fluctuations in driven quantum fluids.
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11
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Li R, Wu Y, Rui Y, Li B, Jiang Y, Ma L, Wu H. Absolute Frequency Measurement of ^{6}Li D Lines with khz-Level Uncertainty. PHYSICAL REVIEW LETTERS 2020; 124:063002. [PMID: 32109124 DOI: 10.1103/physrevlett.124.063002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 12/03/2019] [Indexed: 06/10/2023]
Abstract
We report the precision measurement of the absolute frequencies, hyperfine splitting, and 2P fine structure splitting in cold atoms of ^{6}Li. Using the stabilized optical frequency comb and developed heterodyne detection technique, the photon shot-noise limited optical spectroscopy is achieved. The measurement of absolute frequencies of D_{1} lines is reached with an uncertainty of about 1 kHz, which is 1 order of magnitude more accurate than previous measurements. The hyperfine splitting of the D_{1} line and 2P fine structure splitting of ^{6}Li are 26.103 1 (14) and 10 052.780 4 (18) MHz, respectively, in agreement with recent theoretical calculations. Our results could provide a benchmark to test the theory at the higher precision and help to resolve large discrepancies among previous experiments.
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Affiliation(s)
- Rui Li
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Yuelong Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Yang Rui
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Bo Li
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Yanyi Jiang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Longsheng Ma
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Haibin Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
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12
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Chen JF, Sun CP, Dong H. Achieve higher efficiency at maximum power with finite-time quantum Otto cycle. Phys Rev E 2020; 100:062140. [PMID: 31962481 DOI: 10.1103/physreve.100.062140] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Indexed: 11/07/2022]
Abstract
The optimization of heat engines was intensively explored to achieve higher efficiency while maintaining the output power. However, most investigations were limited to a few finite-time cycles, e.g., the Carnot-like cycle, due to the complexity of the finite-time thermodynamics. In this paper, we propose a class of finite-time engine with quantum Otto cycle, and demonstrate a higher achievable efficiency at maximum power. The current model can be widely utilized, benefitting from the general C/τ^{2} scaling of extra work for a finite-time adiabatic process with long control time τ. We apply the adiabatic perturbation method to the quantum piston model and calculate the efficiency at maximum power, which is validated with an exact solution.
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Affiliation(s)
- Jin-Fu Chen
- Beijing Computational Science Research Center, Beijing 100193, China.,Graduate School of China Academy of Engineering Physics, No. 10 Xibeiwang East Road, Haidian District, Beijing 100193, China
| | - Chang-Pu Sun
- Beijing Computational Science Research Center, Beijing 100193, China.,Graduate School of China Academy of Engineering Physics, No. 10 Xibeiwang East Road, Haidian District, Beijing 100193, China
| | - Hui Dong
- Graduate School of China Academy of Engineering Physics, No. 10 Xibeiwang East Road, Haidian District, Beijing 100193, China
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13
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Oscillatory-like expansion of a Fermionic superfluid. Sci Bull (Beijing) 2020; 65:7-11. [PMID: 36659071 DOI: 10.1016/j.scib.2019.10.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 09/25/2019] [Accepted: 10/14/2019] [Indexed: 01/21/2023]
Abstract
We study the expansion behaviors of a Fermionic superfluid in a cigar-shaped optical dipole trap for the whole BEC-BCS crossover and various temperatures. At low temperature (0.06(1)TF), the atom cloud undergoes an anisotropic hydrodynamic expansion over 30 ms, which behaves like oscillation in the horizontal plane. By analyzing the expansion dynamics according to the superfluid hydrodynamic equation, the effective polytropic index γ¯ of Equation-of-State (EoS) of Fermionic superfluid is extracted. The γ¯ values show a non-monotonic behavior over the BEC-BCS crossover, and have a good agreement with the theoretical results in the unitarity and BEC side. The normalized quasi-frequencies of the oscillatory expansion are measured, which drop significantly from the BEC side to the BCS side and reach a minimum value of 1.73 around 1/kFa=-0.25. Our work improves the understanding of the dynamic properties of strongly interacting Fermi gas.
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14
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Chen JF, Sun CP, Dong H. Boosting the performance of quantum Otto heat engines. Phys Rev E 2019; 100:032144. [PMID: 31640026 DOI: 10.1103/physreve.100.032144] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Indexed: 11/07/2022]
Abstract
To optimize the performance of a heat engine in a finite-time cycle, it is important to understand the finite-time effect of thermodynamic processes. Previously, we have shown that extra work is needed to complete a quantum adiabatic process in finite time, and proved that the extra work follows a C/τ^{2} scaling for long control time τ. There the oscillating part of the extra work is neglected due to the complex energy-level structure of the particular quantum system. However, such oscillation of the extra work cannot be neglected in some quantum systems with simple energy-level structure, e.g., the two-level system or the quantum harmonic oscillator. In this paper, we build the finite-time quantum Otto engine on these simple systems, and find that the oscillating extra work leads to a jagged edge in the constraint relation between the output power and the efficiency. By optimizing the control time of the adiabatic processes, the oscillation in the extra work is utilized to enhance the maximum power and the efficiency. We further design special control schemes with the zero extra work at the specific control time. Compared to the linear control scheme, these special control schemes of the finite-time adiabatic process improve the maximum power and the efficiency of the finite-time Otto engine.
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Affiliation(s)
- Jin-Fu Chen
- Beijing Computational Science Research Center, Beijing 100193, China.,Graduate School of China Academy of Engineering Physics, No. 10 Xibeiwang East Road, Haidian District, Beijing, 100193, China
| | - Chang-Pu Sun
- Beijing Computational Science Research Center, Beijing 100193, China.,Graduate School of China Academy of Engineering Physics, No. 10 Xibeiwang East Road, Haidian District, Beijing, 100193, China
| | - Hui Dong
- Graduate School of China Academy of Engineering Physics, No. 10 Xibeiwang East Road, Haidian District, Beijing, 100193, China
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15
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Zhang P, Zhai H. Scaling symmetry meets topology. Sci Bull (Beijing) 2019; 64:289-290. [PMID: 36659590 DOI: 10.1016/j.scib.2019.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Pengfei Zhang
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
| | - Hui Zhai
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China.
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16
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Wang H, Liu H, Li Y, Liu Y, Wang J, Liu J, Dai JY, Wang Y, Li L, Yan J, Mandrus D, Xie XC, Wang J. Discovery of log-periodic oscillations in ultraquantum topological materials. SCIENCE ADVANCES 2018; 4:eaau5096. [PMID: 30406205 PMCID: PMC6214643 DOI: 10.1126/sciadv.aau5096] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 09/25/2018] [Indexed: 05/30/2023]
Abstract
Quantum oscillations are usually the manifestation of the underlying physical nature in condensed matter systems. Here, we report a new type of log-periodic quantum oscillations in ultraquantum three-dimensional topological materials. Beyond the quantum limit (QL), we observe the log-periodic oscillations involving up to five oscillating cycles (five peaks and five dips) on the magnetoresistance of high-quality single-crystal ZrTe5, virtually showing the clearest feature of discrete scale invariance (DSI). Further, theoretical analyses show that the two-body quasi-bound states can be responsible for the DSI feature. Our work provides a new perspective on the ground state of topological materials beyond the QL.
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Affiliation(s)
- Huichao Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China
| | - Haiwen Liu
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Yanan Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Yongjie Liu
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Junfeng Wang
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jun Liu
- Center of Electron Microscopy, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Ji-Yan Dai
- Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China
| | - Yong Wang
- Center of Electron Microscopy, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Liang Li
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jiaqiang Yan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - David Mandrus
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
| | - X. C. Xie
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
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17
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Deng S, Chenu A, Diao P, Li F, Yu S, Coulamy I, del Campo A, Wu H. Superadiabatic quantum friction suppression in finite-time thermodynamics. SCIENCE ADVANCES 2018; 4:eaar5909. [PMID: 29719865 PMCID: PMC5922798 DOI: 10.1126/sciadv.aar5909] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 03/09/2018] [Indexed: 06/08/2023]
Abstract
Optimal performance of thermal machines is reached by suppressing friction. Friction in quantum thermodynamics results from fast driving schemes that generate nonadiabatic excitations. The far-from-equilibrium dynamics of quantum devices can be tailored by shortcuts to adiabaticity to suppress quantum friction. We experimentally demonstrate friction-free superadiabatic strokes with a trapped unitary Fermi gas as a working substance and establish the equivalence between the superadiabatic work and its adiabatic value.
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Affiliation(s)
- Shujin Deng
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, P. R. China
| | - Aurélia Chenu
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Pengpeng Diao
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, P. R. China
| | - Fang Li
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, P. R. China
| | - Shi Yu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, P. R. China
| | - Ivan Coulamy
- Department of Physics, University of Massachusetts, Boston, MA 02125, USA
- Departamento de Física, Universidade Federal Fluminense, Niterói, Rio de Janeiro, Brazil
| | - Adolfo del Campo
- Department of Physics, University of Massachusetts, Boston, MA 02125, USA
| | - Haibin Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, P. R. China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
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18
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Deng S, Diao P, Li F, Yu Q, Yu S, Wu H. Observation of Dynamical Super-Efimovian Expansion in a Unitary Fermi Gas. PHYSICAL REVIEW LETTERS 2018; 120:125301. [PMID: 29694076 DOI: 10.1103/physrevlett.120.125301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Indexed: 06/08/2023]
Abstract
We report an observation of a dynamical super Efimovian expansion in a strongly interacting Fermi gas by engineering time dependent external harmonic trap frequencies. When the trap frequency is tailored as [1/4t^{2}+1/t^{2}λlog^{2}(t/t_{*})]^{1/2}, where t_{*} and λ are two controllable parameters, and the change is faster than a critical value, the expansion of such a quantum gas shows novel dynamics that share the same characteristics as the super Efimov effect. A clear double-log periodicity with discrete geometric scaling emerges for the cloud size in the expansion. The universality of such scaling dynamics is verified both in the noninteracting and in the unitarity limit of Fermi gas. Moreover, the measured energy scaling reveals that the potential and internal energy also show double-log periodicity with a π/2 phase difference, but the total energy is monotonically decreased. Observing super Efimovian evolution represents a paradigm in probing universal properties and allows us in a new way to study many-body nonequilibrium dynamics with experiments.
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Affiliation(s)
- Shujin Deng
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Pengpeng Diao
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Fang Li
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Qianli Yu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Shi Yu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
| | - Haibin Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, People's Republic of China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
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