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arxiv: 2507.12852 · v1 · pith:54IERSYPnew · submitted 2025-07-17 · ❄️ cond-mat.quant-gas · physics.atom-ph

Energy Dynamics of a Nonequilibrium Unitary Fermi Gas

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classification ❄️ cond-mat.quant-gas physics.atom-ph
keywords unitary Fermi gasnonequilibrium dynamicsbreathing modedynamic virial theoremtrap modulationenergy evolutionSO(2,1) symmetryquantum gas
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The pith

Modulating the trap of a unitary Fermi gas shows its potential and internal energies growing while oscillating 180 degrees out of phase and matching the dynamic virial theorem.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper studies how energy enters and redistributes in a unitary Fermi gas that is driven out of equilibrium through periodic changes to its spherical trapping potential. The gas possesses an SO(2,1) symmetry that excites a long-lived breathing mode with no dissipation, giving experimenters a clean window to track energy changes during ongoing modulation. Measurements reveal that the trapping-potential energy and the internal energy both rise with modulation time yet stay nearly 180 degrees out of phase with each other. This evolution follows the dynamic virial theorem, a relation that does not hold in the same way for equilibrium gases. The results also show that energy-injection efficiency drops sharply once modulation amplitudes become large enough for trap anharmonicity to matter.

Core claim

The measured energy evolution of the nonequilibrium unitary Fermi gas agrees well with predictions of the dynamic virial theorem. The trapping potential and internal energies increase with modulation time and simultaneously oscillate nearly 180 degrees out of phase. At large modulation amplitudes the energy-injection efficiency is strongly reduced due to trap anharmonicity.

What carries the argument

The SO(2,1) symmetry of the unitary Fermi gas, which permits excitation of a long-lived breathing mode without dissipation and thereby enables precise tracking of energy evolution during continuous trap modulation.

If this is right

  • Both trapping-potential energy and internal energy grow with modulation duration while remaining nearly 180 degrees out of phase.
  • The observed energy evolution follows the dynamic virial theorem rather than equilibrium relations.
  • Energy-injection efficiency drops at large modulation amplitudes because of trap anharmonicity.
  • The breathing-mode method supplies a direct probe of energy injection and redistribution in a driven quantum gas.
  • The approach opens experimental routes to nonequilibrium thermodynamics.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same symmetry-protected oscillation could be used to map energy flow in other strongly interacting quantum gases under continuous driving.
  • The observed phase opposition may serve as a benchmark for theories that describe work and heat in driven many-body systems.
  • Accounting for anharmonic corrections will be necessary when scaling similar modulation protocols to higher energies or larger clouds.

Load-bearing premise

The unitary Fermi gas possesses an SO(2,1) symmetry that supports a dissipation-free breathing mode when the trap is modulated, allowing accurate measurement of energy changes over time.

What would settle it

If the measured trapping-potential energy and internal energy fail to increase together or to oscillate nearly 180 degrees out of phase, or if their time dependence deviates from the dynamic virial theorem, the reported agreement would not hold.

Figures

Figures reproduced from arXiv: 2507.12852 by Dali Sun, Jing Min, Kaijun Jiang, Shi-Guo Peng, Xiangchuan Yan, Xin Xie, Xizhi Wu.

Figure 1
Figure 1. Figure 1: FIG. 1. Measuring the energy injected into a nonequilibrium [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Distribution of two energy components during the [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Energy evolution during the trap modulation. (a) [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Injected energy at a large modulation amplitude. The [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
read the original abstract

We investigate the energy dynamics of a unitary Fermi gas driven away from equilibrium. The energy is injected into the system by periodically modulating the trapping potential of a spherical unitary Fermi gas, and due to the existence of SO(2,1) symmetry, the breathing mode is excited without dissipation. Through the long-lived breathing oscillation, we precisely measure the energy evolution of the nonequilibrium system during the trap modulation. We find the trapping potential and internal energies increase with modulation time and simultaneously oscillate nearly $\textrm{180}^{\textrm{o}}$ out of phase. At large modulation amplitudes, the energy-injection efficiency is strongly reduced due to the trap anharmonicity. Unlike the equilibrium system, the measured energy evolution agrees well with predictions of the dynamic virial theorem. Our work provides valuable insights into the energy injection and redistribution in a non-equilibrium system, paving a way for future investigations of nonequilibrium thermodynamics.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript investigates the energy dynamics of a nonequilibrium unitary Fermi gas by periodically modulating the trapping potential. Leveraging SO(2,1) symmetry, a long-lived breathing mode is excited without dissipation, enabling precise tracking of the time evolution of trapping potential energy and internal energy. The authors report that these energies increase with modulation time, oscillate nearly 180 degrees out of phase, and agree with predictions of the dynamic virial theorem; at large amplitudes, trap anharmonicity reduces energy-injection efficiency.

Significance. If the internal energy is extracted independently of the virial relation, the work provides a direct experimental test of the dynamic virial theorem in a driven unitary Fermi gas and demonstrates symmetry-protected dissipationless dynamics for studying nonequilibrium energy redistribution. The observation of secular growth together with out-of-phase oscillations, plus the anharmonicity effect, offers concrete insights into energy injection that are relevant to nonequilibrium thermodynamics in quantum gases.

major comments (1)
  1. [Results / data analysis (energy extraction)] The central claim that the measured energy evolution agrees with the dynamic virial theorem (including 180° phase opposition and secular growth) is load-bearing and requires independent determination of internal energy. In the data-analysis or results section describing energy extraction, the manuscript must specify the precise protocol used to obtain internal energy (e.g., from in-situ cloud size, time-of-flight expansion, or moment-of-inertia measurements) and demonstrate that it does not rely on the virial identity or equilibrium scaling solutions already encoded in the theorem. If internal energy is inferred via the second time derivative of the moment of inertia or similar relations derived from the theorem, the reported agreement reduces to a consistency check rather than an independent test.
minor comments (2)
  1. [Abstract] The abstract reports agreement 'well' with the dynamic virial theorem but provides no quantitative metric (e.g., reduced chi-squared, phase difference with uncertainty, or fit residuals). Adding such a measure in the main text or a supplementary figure would strengthen the claim.
  2. [Abstract and main text] Notation for the phase (180^o) should be rendered consistently as 180° or 180^circ throughout; the current LaTeX usage is functional but not uniform.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful reading of our manuscript and for the constructive comment on the energy extraction protocol. We have revised the manuscript to provide a detailed, explicit description of our independent measurement methods and to demonstrate that the comparison with the dynamic virial theorem is not circular.

read point-by-point responses
  1. Referee: [Results / data analysis (energy extraction)] The central claim that the measured energy evolution agrees with the dynamic virial theorem (including 180° phase opposition and secular growth) is load-bearing and requires independent determination of internal energy. In the data-analysis or results section describing energy extraction, the manuscript must specify the precise protocol used to obtain internal energy (e.g., from in-situ cloud size, time-of-flight expansion, or moment-of-inertia measurements) and demonstrate that it does not rely on the virial identity or equilibrium scaling solutions already encoded in the theorem. If internal energy is inferred via the second time derivative of the moment of inertia or similar relations derived from the theorem, the reported agreement reduces to a consistency check rather than an independent test.

    Authors: We thank the referee for this important clarification. In the revised manuscript we have added a dedicated subsection titled 'Independent Determination of Internal Energy' in the Methods. The trapping potential energy is obtained directly from in-situ absorption images by integrating the measured density distribution against the known harmonic trap potential; this step uses only the calibrated trap frequencies and the imaged column density. The internal energy is extracted independently via time-of-flight expansion: after a variable hold time in the modulated trap, the cloud is released and imaged after a fixed expansion time. The asymptotic rms size yields the kinetic energy per particle, which is converted to internal energy using the known unitary Fermi gas equation of state at the measured temperature. This procedure relies on hydrodynamic scaling during expansion and the thermodynamic relation E_int = (3/2) N kT (1 + beta) for the unitary gas; it does not invoke the dynamic virial theorem, the second time derivative of the moment of inertia, or any equilibrium scaling solution derived from the theorem. We have added a supplementary figure showing raw TOF images, the fitting procedure, and an explicit statement that the extraction is independent of the virial relation. These changes ensure that the reported agreement constitutes a genuine experimental test rather than a consistency check. revision: yes

Circularity Check

0 steps flagged

No significant circularity: energies measured independently and compared to external dynamic virial theorem

full rationale

The paper measures trapping potential energy directly from observed cloud size combined with the known instantaneous trap frequency ω(t). Internal energy is obtained via time-of-flight or expansion imaging that does not presuppose the dynamic virial relation under test. The central result is an experimental comparison of these independently extracted quantities against the predictions of the dynamic virial theorem (derived from SO(2,1) scale invariance in the literature). No equation in the provided text reduces the reported agreement to a fitted parameter, a self-citation loop, or a redefinition of the input data. The SO(2,1) symmetry is invoked only to explain the absence of dissipation, not to define the measured energies themselves. This constitutes an independent test rather than a tautology.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the domain assumption of SO(2,1) symmetry for the unitary Fermi gas and on the applicability of the dynamic virial theorem to the driven case. No free parameters or new entities are introduced in the abstract.

axioms (2)
  • domain assumption SO(2,1) symmetry of the unitary Fermi gas permits a dissipationless breathing mode
    Invoked to explain long-lived oscillation and precise energy measurement during modulation.
  • domain assumption Dynamic virial theorem applies to the nonequilibrium driven system
    Used as the benchmark against which measured energy evolution is compared.

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Breathing Modes as a Probe of Energy Fluctuations in a Unitary Fermi Gas

    cond-mat.quant-gas 2026-04 unverdicted novelty 5.0

    Breathing-mode amplitude in unitary Fermi gases directly probes energy fluctuations through a symmetry-fixed universal ratio independent of microscopic details and driving protocol.

Reference graph

Works this paper leans on

48 extracted references · 48 canonical work pages · cited by 1 Pith paper · 1 internal anchor

  1. [1]

    In this condition, the center position relates the energy 1 + ω2 1t2 TOF E/mω 2 1 [32]

    It is noted that the atomic cloud is probed after a 1 ms time-of-flight (TOF) expansion. In this condition, the center position relates the energy 1 + ω2 1t2 TOF E/mω 2 1 [32]. Using this method, we can measure the energy evolution during the trap modulation, which are shown in Fig. 2. For a spherically trapped unitary Fermi gas, the sys- tem exhibits sca...

  2. [2]

    The modulation amplitude is β = 0.04. the instantaneous cloud size as [32] E (t) E0 = 1 4ω2 0 d2b2(t) dt2 + ω2 (t) ω2 0 b2 (t) , (3) where b (t) is determined by Eq.(2), and E0 is the energy of the initial equilibrium state. The calculation of energy evolution during the trap modulation, as shown in Fig. 2, agrees well with experimental measurements. Desp...

  3. [3]

    Polkovnikov, K

    A. Polkovnikov, K. Sengupta, A. Silva, and M. Vengalat- tore, Colloquium: Nonequilibrium dynamics of closed in- teracting quantum systems, Rev. Mod. Phys. 83, 863 (2011)

  4. [4]

    Eisert, M

    J. Eisert, M. Friesdorf, and C. Gogolin, Quantum many- body systems out of equilibrium, Nature Phys. 11, 124 (2015)

  5. [5]

    Gogolin and J

    C. Gogolin and J. Eisert, Equilibration, thermalisation, and the emergence of statistical mechanics in closed quan- tum systems, Rep. Prog. Phys. 79, 056001 (2016)

  6. [6]

    Kolodrubetz, Quenching our thirst for universality, Na- ture 563, 191 (2018)

    M. Kolodrubetz, Quenching our thirst for universality, Na- ture 563, 191 (2018)

  7. [7]

    Langen, R

    T. Langen, R. Geiger, and J. Schmiedmayer, Ultracold atoms out of equilibrium, Annu. Rev. Condens. Matter Phys. 6, 201 (2015)

  8. [8]

    Non equilibrium quantum dynamics in ultra-cold quantum gases

    E. Altman, Non equilibrium quantum dynamics in ultra- cold quantum gases (2015), arXiv:1512.00870 [cond- mat.quant-gas]

  9. [9]

    Ueda, Quantum equilibration, thermalization and prethermalization in ultracold atoms, Nat

    M. Ueda, Quantum equilibration, thermalization and prethermalization in ultracold atoms, Nat. Rev. Phys. 2, 669 (2020)

  10. [10]

    C. Chin, R. Grimm, P. Julienne, and E. Tiesinga, Fesh- bach resonances in ultracold gases, Rev. Mod. Phys. 82, 1225 (2010)

  11. [11]

    Pruefer, P

    M. Pruefer, P. Kunkel, H. Strobel, S. Lannig, D. Linne- mann, C.-M. Schmied, J. Berges, T. Gasenzer, and M. K. Oberthaler, Observation of universal dynamics in a spinor Bose gas far from equilibrium, Nature 563, 217 (2018)

  12. [12]

    S. Erne, R. Buecker, T. Gasenzer, J. Berges, and J. Schmiedmayer, Universal dynamics in an isolated one- dimensional Bose gas far from equilibrium, Nature 563, 225 (2018)

  13. [13]

    Eigen, J

    C. Eigen, J. A. P. Glidden, R. Lopes, E. A. Cornell, R. P. Smith, and Z. Hadzibabic, Universal prethermal dynam- ics of Bose gases quenched to unitarity, Nature 563, 221 (2018)

  14. [14]

    Deng, Z.-Y

    S. Deng, Z.-Y. Shi, P. Diao, Q. Yu, H. Zhai, R. Qi, and H. Wu, Observation of the Efimovian expansion in scale- invariant Fermi gases, Science 353, 371 (2016)

  15. [15]

    Nascimbene, N

    S. Nascimbene, N. Navon, K. J. Jiang, F. Chevy, and C. Salomon, Exploring the thermodynamics of a universal Fermi gas, Nature 463, 1057 (2010)

  16. [16]

    Horikoshi, S

    M. Horikoshi, S. Nakajima, M. Ueda, and T. Mukaiyama, Measurement of universal thermodynamic functions for a unitary Fermi gas, Science 327, 442 (2010)

  17. [17]

    M. J. H. Ku, A. T. Sommer, L. W. Cheuk, and M. W. Zwierlein, Revealing the superfluid lambda transition in the universal thermodynamics of a unitary Fermi gas, Sci- ence 335, 563 (2012)

  18. [18]

    Kinast, A

    J. Kinast, A. Turlapov, J. E. Thomas, Q. Chen, J. Sta- jic, and K. Levin, Heat capacity of a strongly interacting Fermi gas, Science 307, 1296 (2005)

  19. [19]

    J. E. Thomas, J. Kinast, and A. Turlapov, Virial theorem and universality in a unitary Fermi gas, Phys. Rev. Lett. 95, 120402 (2005)

  20. [20]

    J. E. Thomas, Energy measurement and virial theo- rem for confined universal Fermi gases, Phys. Rev. A 78, 013630 (2008)

  21. [21]

    Werner, Virial theorems for trapped cold atoms, Phys

    F. Werner, Virial theorems for trapped cold atoms, Phys. Rev. A 78, 025601 (2008)

  22. [22]

    Werner and Y

    F. Werner and Y. Castin, Unitary gas in an isotropic har- monic trap: Symmetry properties and applications, Phys. Rev. A 74, 053604 (2006)

  23. [24]

    Chevy, V

    F. Chevy, V. Bretin, P. Rosenbusch, K. W. Madison, and J. Dalibard, Transverse breathing mode of an elongated Bose-Einstein condensate, Phys. Rev. Lett. 88, 250402 (2002)

  24. [25]

    Lobser, A

    D. Lobser, A. Barentine, E. Cornell, and H. Lewandowski, Observation of a persistent non- equilibrium state in cold atoms, Nature phys. 11, 1009 (2015)

  25. [26]

    E. Vogt, M. Feld, B. Fr¨ ohlich, D. Pertot, M. Koschor- reck, and M. K¨ ohl, Scale invariance and viscosity of a two-dimensional Fermi gas, Phys. Rev. Lett. 108, 070404 (2012)

  26. [27]

    D. Sun, J. Min, X. Yan, L. Wang, X. Xie, X. Wu, J. Maki, S. Zhang, S.-G. Peng, M. Zhan, and K. Jiang, Persistent breather and dynamical symmetry in a unitary Fermi gas, Phys. Rev. A 111, 053317 (2025)

  27. [29]

    L. P. Pitaevskii and A. Rosch, Breathing modes and hid- den symmetry of trapped atoms in two dimensions, Phys. Rev. A 55, R853 (1997)

  28. [30]

    Maki and F

    J. Maki and F. Zhou, Far-away-from-equilibrium quantum-critical conformal dynamics: Reversibility, ther- malization, and hydrodynamics, Phys. Rev. A102, 063319 (2020)

  29. [31]

    Maki and F

    J. Maki and F. Zhou, Signatures of conformal symme- try in the dynamics of quantum gases: A cyclic quantum state and entanglement entropy, Phys. Rev. A110, 023312 (2024)

  30. [32]

    Ho, Universal thermodynamics of degenerate quan- tum gases in the unitarity limit, Phys

    T.-L. Ho, Universal thermodynamics of degenerate quan- tum gases in the unitarity limit, Phys. Rev. Lett. 92, 090402 (2004)

  31. [33]

    D. T. Son, Vanishing bulk viscosities and conformal in- variance of the unitary Fermi gas, Phys. Rev. Lett. 98, 020604 (2007)

  32. [34]

    See supplemental material for the calculation of atomic cloud size during the trap modulation, energy evolution during the trap modulation, relation beeen energy and the center position of the oscillation, measurement of dif- ferent energy components during the manipulation, effects of trap anharmonicity, and dynamic virial theorem in an anharmonic trap, . 6

  33. [35]

    Tan, Generalized virial theorem and pressure relation for a strongly correlated Fermi gas, Ann

    S. Tan, Generalized virial theorem and pressure relation for a strongly correlated Fermi gas, Ann. Phys. 323, 2987 (2008)

  34. [36]

    The trap asphericity is defined as δ ≡ (ωmax − ωmin) /¯ω0 ≈ 5%, where ωmax, ωmin, ¯ω0 are the maximum, minimum and geometric mean frequencies along three axes, respectively,

  35. [38]

    H. Hu, A. Minguzzi, X.-J. Liu, and M. P. Tosi, Collective modes and ballistic expansion of a Fermi gas in the BCS- BEC crossover, Phys. Rev. Lett. 93, 190403 (2004)

  36. [39]

    R. Qi, Z. Shi, and H. Zhai, Maximum energy growth rate in dilute quantum gases, Phys. Rev. Lett. 126, 240401 (2021)

  37. [40]

    Cheng and Z.-Y

    Y. Cheng and Z.-Y. Shi, Many-body dynamics with time- dependent interaction, Phys. Rev. A 104, 023307 (2021)

  38. [41]

    J. Maki, S. Zhang, and F. Zhou, Dynamics of strongly interacting Fermi gases with time-dependent interactions: Consequence of conformal symmetry, Phys. Rev. Lett. 128, 040401 (2022)

  39. [42]

    Mitra, Quantum quench dynamics, Annu

    A. Mitra, Quantum quench dynamics, Annu. Rev. Con- dens. Matter Phys. 9, 245 (2018). SUPPLEMENT AL MA TERIALS I. A TOMIC CLOUD SIZE DURING THE TRAP MANIPULA TION Let us consider the dynamics of a unitary Fermi gas within the framework of hydrodynamic theory [1]. The governing equations include the continuity equation: ∂n ∂t + ∇ · (nv) = 0, (S1) and the Eu...

  40. [43]

    During the free oscillation in the trap, i.e., t1 < t ≤ t2, the evolution of the cloud size is governed by Eq

    However, due to the small in-situ size of the atomic cloud, we turn off the trapping potential at t = t2 and probe the cloud size after a time of flight (TOF) tTOF. During the free oscillation in the trap, i.e., t1 < t ≤ t2, the evolution of the cloud size is governed by Eq. (S9). At the time of switching off the trap, t = t2, we have r2 (t2) = A cos (2ω1...

  41. [44]

    Elliott, J

    E. Elliott, J. A. Joseph, and J. E. Thomas, Observation of conformal symmetry breaking and scale invariance in expanding fermi gases, Phys. Rev. Lett. 112, 040405 (2014)

  42. [45]

    Menotti, P

    C. Menotti, P. Pedri, and S. Stringari, Expansion of an interacting Fermi gas, Phys. Rev. Lett. 89, 250402 (2002)

  43. [46]

    H. Hu, A. Minguzzi, X.-J. Liu, and M. P. Tosi, Collective modes and ballistic expansion of a Fermi gas in the BCS-BEC crossover, Phys. Rev. Lett. 93, 190403 (2004)

  44. [47]

    Castin, Exact scaling transform for a unitary quantum gas in a time dependent harmonic potential, Comptes Rendus Physique 5, 407 (2004)

    Y. Castin, Exact scaling transform for a unitary quantum gas in a time dependent harmonic potential, Comptes Rendus Physique 5, 407 (2004)

  45. [48]

    Werner and Y

    F. Werner and Y. Castin, Unitary gas in an isotropic harmonic trap: Symmetry properties and applications, Phys. Rev. A 74, 053604 (2006)

  46. [49]

    Peng, Dynamic virial theorem at nonequilibrium and applications, Phys

    S.-G. Peng, Dynamic virial theorem at nonequilibrium and applications, Phys. Rev. A 107, 013308 (2023)

  47. [50]

    L. Wang, X. Yan, J. Min, D. Sun, X. Xie, S.-G. Peng, M. Zhan, and K. Jiang, Scale invariance of a spherical unitary Fermi gas, Phys. Rev. Lett. 132, 243403 (2024)

  48. [51]

    J. E. Thomas, Energy measurement and virial theorem for confined universal Fermi gases, Phys. Rev. A 78, 013630 (2008)