---
_id: '9606'
abstract:
- lang: eng
  text: Sound propagation is a macroscopic manifestation of the interplay between
    the equilibrium thermodynamics and the dynamical transport properties of fluids.
    Here, for a two-dimensional system of ultracold fermions, we calculate the first
    and second sound velocities across the whole BCS-BEC crossover, and we analyze
    the system response to an external perturbation. In the low-temperature regime
    we reproduce the recent measurements [Phys. Rev. Lett. 124, 240403 (2020)] of
    the first sound velocity, which, due to the decoupling of density and entropy
    fluctuations, is the sole mode excited by a density probe. Conversely, a heat
    perturbation excites only the second sound, which, being sensitive to the superfluid
    depletion, vanishes in the deep BCS regime and jumps discontinuously to zero at
    the Berezinskii-Kosterlitz-Thouless superfluid transition. A mixing between the
    modes occurs only in the finite-temperature BEC regime, where our theory converges
    to the purely bosonic results.
acknowledgement: "G.B. acknowledges support from the Austrian Science Fund (FWF),
  under Project No. M2641-N27. This work was\r\npartially supported by the University
  of Padua, BIRD project “Superfluid properties of Fermi gases in optical potentials.”\r\nThe
  authors thank Miki Ota, Tomoki Ozawa, Sandro Stringari, Tilman Enss, Hauke Biss,
  Henning Moritz, and Nicolò Defenu for fruitful discussions. The authors thank Henning
  Moritz and Markus Bohlen for providing their experimental\r\ndata."
article_number: L061303
article_processing_charge: No
article_type: letter_note
arxiv: 1
author:
- first_name: A.
  full_name: Tononi, A.
  last_name: Tononi
- first_name: Alberto
  full_name: Cappellaro, Alberto
  id: 9d13b3cb-30a2-11eb-80dc-f772505e8660
  last_name: Cappellaro
  orcid: 0000-0001-6110-2359
- first_name: Giacomo
  full_name: Bighin, Giacomo
  id: 4CA96FD4-F248-11E8-B48F-1D18A9856A87
  last_name: Bighin
  orcid: 0000-0001-8823-9777
- first_name: L.
  full_name: Salasnich, L.
  last_name: Salasnich
citation:
  ama: Tononi A, Cappellaro A, Bighin G, Salasnich L. Propagation of first and second
    sound in a two-dimensional Fermi superfluid. <i>Physical Review A</i>. 2021;103(6).
    doi:<a href="https://doi.org/10.1103/PhysRevA.103.L061303">10.1103/PhysRevA.103.L061303</a>
  apa: Tononi, A., Cappellaro, A., Bighin, G., &#38; Salasnich, L. (2021). Propagation
    of first and second sound in a two-dimensional Fermi superfluid. <i>Physical Review
    A</i>. American Physical Society. <a href="https://doi.org/10.1103/PhysRevA.103.L061303">https://doi.org/10.1103/PhysRevA.103.L061303</a>
  chicago: Tononi, A., Alberto Cappellaro, Giacomo Bighin, and L. Salasnich. “Propagation
    of First and Second Sound in a Two-Dimensional Fermi Superfluid.” <i>Physical
    Review A</i>. American Physical Society, 2021. <a href="https://doi.org/10.1103/PhysRevA.103.L061303">https://doi.org/10.1103/PhysRevA.103.L061303</a>.
  ieee: A. Tononi, A. Cappellaro, G. Bighin, and L. Salasnich, “Propagation of first
    and second sound in a two-dimensional Fermi superfluid,” <i>Physical Review A</i>,
    vol. 103, no. 6. American Physical Society, 2021.
  ista: Tononi A, Cappellaro A, Bighin G, Salasnich L. 2021. Propagation of first
    and second sound in a two-dimensional Fermi superfluid. Physical Review A. 103(6),
    L061303.
  mla: Tononi, A., et al. “Propagation of First and Second Sound in a Two-Dimensional
    Fermi Superfluid.” <i>Physical Review A</i>, vol. 103, no. 6, L061303, American
    Physical Society, 2021, doi:<a href="https://doi.org/10.1103/PhysRevA.103.L061303">10.1103/PhysRevA.103.L061303</a>.
  short: A. Tononi, A. Cappellaro, G. Bighin, L. Salasnich, Physical Review A 103
    (2021).
date_created: 2021-06-27T22:01:49Z
date_published: 2021-06-01T00:00:00Z
date_updated: 2023-08-10T13:37:25Z
day: '01'
department:
- _id: MiLe
doi: 10.1103/PhysRevA.103.L061303
external_id:
  arxiv:
  - '2009.06491'
  isi:
  - '000662296700014'
intvolume: '       103'
isi: 1
issue: '6'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/2009.06491
month: '06'
oa: 1
oa_version: Preprint
publication: Physical Review A
publication_identifier:
  eissn:
  - '24699934'
  issn:
  - '24699926'
publication_status: published
publisher: American Physical Society
quality_controlled: '1'
scopus_import: '1'
status: public
title: Propagation of first and second sound in a two-dimensional Fermi superfluid
type: journal_article
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 103
year: '2021'
...
---
_id: '8319'
abstract:
- lang: eng
  text: We demonstrate that releasing atoms into free space from an optical lattice
    does not deteriorate cavity-generated spin squeezing for metrological purposes.
    In this work, an ensemble of 500000 spin-squeezed atoms in a high-finesse optical
    cavity with near-uniform atom-cavity coupling is prepared, released into free
    space, recaptured in the cavity, and probed. Up to ∼10 dB of metrologically relevant
    squeezing is retrieved for 700μs free-fall times, and decaying levels of squeezing
    are realized for up to 3 ms free-fall times. The degradation of squeezing results
    from loss of atom-cavity coupling homogeneity between the initial squeezed state
    generation and final collective state readout. A theoretical model is developed
    to quantify this degradation and this model is experimentally validated.
acknowledgement: We thank N. Engelsen for comments on the manuscript. This work was
  supported by the Office of Naval Research, Vannevar Bush Faculty Fellowship, Department
  of Energy, and Defense Threat Reduction Agency. R.K. was partly supported by the
  AQT/INQNET program at Caltech.
article_number: '012224'
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Yunfan
  full_name: Wu, Yunfan
  last_name: Wu
- first_name: Rajiv
  full_name: Krishnakumar, Rajiv
  last_name: Krishnakumar
- first_name: Julián
  full_name: Martínez-Rincón, Julián
  last_name: Martínez-Rincón
- first_name: Benjamin K.
  full_name: Malia, Benjamin K.
  last_name: Malia
- first_name: Onur
  full_name: Hosten, Onur
  id: 4C02D85E-F248-11E8-B48F-1D18A9856A87
  last_name: Hosten
  orcid: 0000-0002-2031-204X
- first_name: Mark A.
  full_name: Kasevich, Mark A.
  last_name: Kasevich
citation:
  ama: Wu Y, Krishnakumar R, Martínez-Rincón J, Malia BK, Hosten O, Kasevich MA. Retrieval
    of cavity-generated atomic spin squeezing after free-space release. <i>Physical
    Review A</i>. 2020;102(1). doi:<a href="https://doi.org/10.1103/PhysRevA.102.012224">10.1103/PhysRevA.102.012224</a>
  apa: Wu, Y., Krishnakumar, R., Martínez-Rincón, J., Malia, B. K., Hosten, O., &#38;
    Kasevich, M. A. (2020). Retrieval of cavity-generated atomic spin squeezing after
    free-space release. <i>Physical Review A</i>. American Physical Society. <a href="https://doi.org/10.1103/PhysRevA.102.012224">https://doi.org/10.1103/PhysRevA.102.012224</a>
  chicago: Wu, Yunfan, Rajiv Krishnakumar, Julián Martínez-Rincón, Benjamin K. Malia,
    Onur Hosten, and Mark A. Kasevich. “Retrieval of Cavity-Generated Atomic Spin
    Squeezing after Free-Space Release.” <i>Physical Review A</i>. American Physical
    Society, 2020. <a href="https://doi.org/10.1103/PhysRevA.102.012224">https://doi.org/10.1103/PhysRevA.102.012224</a>.
  ieee: Y. Wu, R. Krishnakumar, J. Martínez-Rincón, B. K. Malia, O. Hosten, and M.
    A. Kasevich, “Retrieval of cavity-generated atomic spin squeezing after free-space
    release,” <i>Physical Review A</i>, vol. 102, no. 1. American Physical Society,
    2020.
  ista: Wu Y, Krishnakumar R, Martínez-Rincón J, Malia BK, Hosten O, Kasevich MA.
    2020. Retrieval of cavity-generated atomic spin squeezing after free-space release.
    Physical Review A. 102(1), 012224.
  mla: Wu, Yunfan, et al. “Retrieval of Cavity-Generated Atomic Spin Squeezing after
    Free-Space Release.” <i>Physical Review A</i>, vol. 102, no. 1, 012224, American
    Physical Society, 2020, doi:<a href="https://doi.org/10.1103/PhysRevA.102.012224">10.1103/PhysRevA.102.012224</a>.
  short: Y. Wu, R. Krishnakumar, J. Martínez-Rincón, B.K. Malia, O. Hosten, M.A. Kasevich,
    Physical Review A 102 (2020).
date_created: 2020-08-30T22:01:10Z
date_published: 2020-07-30T00:00:00Z
date_updated: 2024-02-28T13:11:28Z
day: '30'
department:
- _id: OnHo
doi: 10.1103/PhysRevA.102.012224
external_id:
  arxiv:
  - '1912.08334'
  isi:
  - '000555104200011'
intvolume: '       102'
isi: 1
issue: '1'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/1912.08334
month: '07'
oa: 1
oa_version: Preprint
publication: Physical Review A
publication_identifier:
  eissn:
  - '24699934'
  issn:
  - '24699926'
publication_status: published
publisher: American Physical Society
quality_controlled: '1'
scopus_import: '1'
status: public
title: Retrieval of cavity-generated atomic spin squeezing after free-space release
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 102
year: '2020'
...
---
_id: '6632'
abstract:
- lang: eng
  text: We consider a two-component Bose gas in two dimensions at a low temperature
    with short-range repulsive interaction. In the coexistence phase where both components
    are superfluid, interspecies interactions induce a nondissipative drag between
    the two superfluid flows (Andreev-Bashkin effect). We show that this behavior
    leads to a modification of the usual Berezinskii-Kosterlitz-Thouless (BKT) transition
    in two dimensions. We extend the renormalization of the superfluid densities at
    finite temperature using the renormalization-group approach and find that the
    vortices of one component have a large influence on the superfluid properties
    of the other, mediated  by  the  nondissipative  drag.  The  extended  BKT  flow  equations  indicate  that  the  occurrence  of  the
    vortex unbinding transition in one of the components can induce the breakdown
    of superfluidity also in the other, leading to a locking phenomenon for the critical
    temperatures of the two gases.
article_number: '063627'
article_processing_charge: No
arxiv: 1
author:
- first_name: Volker
  full_name: Karle, Volker
  last_name: Karle
- first_name: Nicolò
  full_name: Defenu, Nicolò
  last_name: Defenu
- first_name: Tilman
  full_name: Enss, Tilman
  last_name: Enss
citation:
  ama: Karle V, Defenu N, Enss T. Coupled superfluidity of binary Bose mixtures in
    two dimensions. <i>Physical Review A</i>. 2019;99(6). doi:<a href="https://doi.org/10.1103/PhysRevA.99.063627">10.1103/PhysRevA.99.063627</a>
  apa: Karle, V., Defenu, N., &#38; Enss, T. (2019). Coupled superfluidity of binary
    Bose mixtures in two dimensions. <i>Physical Review A</i>. American Physical Society.
    <a href="https://doi.org/10.1103/PhysRevA.99.063627">https://doi.org/10.1103/PhysRevA.99.063627</a>
  chicago: Karle, Volker, Nicolò Defenu, and Tilman Enss. “Coupled Superfluidity of
    Binary Bose Mixtures in Two Dimensions.” <i>Physical Review A</i>. American Physical
    Society, 2019. <a href="https://doi.org/10.1103/PhysRevA.99.063627">https://doi.org/10.1103/PhysRevA.99.063627</a>.
  ieee: V. Karle, N. Defenu, and T. Enss, “Coupled superfluidity of binary Bose mixtures
    in two dimensions,” <i>Physical Review A</i>, vol. 99, no. 6. American Physical
    Society, 2019.
  ista: Karle V, Defenu N, Enss T. 2019. Coupled superfluidity of binary Bose mixtures
    in two dimensions. Physical Review A. 99(6), 063627.
  mla: Karle, Volker, et al. “Coupled Superfluidity of Binary Bose Mixtures in Two
    Dimensions.” <i>Physical Review A</i>, vol. 99, no. 6, 063627, American Physical
    Society, 2019, doi:<a href="https://doi.org/10.1103/PhysRevA.99.063627">10.1103/PhysRevA.99.063627</a>.
  short: V. Karle, N. Defenu, T. Enss, Physical Review A 99 (2019).
date_created: 2019-07-14T21:59:17Z
date_published: 2019-06-28T00:00:00Z
date_updated: 2024-02-28T13:12:34Z
day: '28'
department:
- _id: MiLe
doi: 10.1103/PhysRevA.99.063627
external_id:
  arxiv:
  - '1903.06759'
  isi:
  - '000473133600007'
intvolume: '        99'
isi: 1
issue: '6'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/1903.06759
month: '06'
oa: 1
oa_version: Preprint
publication: Physical Review A
publication_identifier:
  eissn:
  - '24699934'
  issn:
  - '24699926'
publication_status: published
publisher: American Physical Society
quality_controlled: '1'
scopus_import: '1'
status: public
title: Coupled superfluidity of binary Bose mixtures in two dimensions
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 99
year: '2019'
...