--- _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 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. Physical Review A. 2021;103(6). doi:10.1103/PhysRevA.103.L061303 apa: Tononi, A., Cappellaro, A., Bighin, G., & Salasnich, L. (2021). Propagation of first and second sound in a two-dimensional Fermi superfluid. Physical Review A. American Physical Society. https://doi.org/10.1103/PhysRevA.103.L061303 chicago: Tononi, A., Alberto Cappellaro, Giacomo Bighin, and L. Salasnich. “Propagation of First and Second Sound in a Two-Dimensional Fermi Superfluid.” Physical Review A. American Physical Society, 2021. https://doi.org/10.1103/PhysRevA.103.L061303. ieee: A. Tononi, A. Cappellaro, G. Bighin, and L. Salasnich, “Propagation of first and second sound in a two-dimensional Fermi superfluid,” Physical Review A, 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.” Physical Review A, vol. 103, no. 6, L061303, American Physical Society, 2021, doi:10.1103/PhysRevA.103.L061303. 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 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. Physical Review A. 2020;102(1). doi:10.1103/PhysRevA.102.012224 apa: Wu, Y., Krishnakumar, R., Martínez-Rincón, J., Malia, B. K., Hosten, O., & Kasevich, M. A. (2020). Retrieval of cavity-generated atomic spin squeezing after free-space release. Physical Review A. American Physical Society. https://doi.org/10.1103/PhysRevA.102.012224 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.” Physical Review A. American Physical Society, 2020. https://doi.org/10.1103/PhysRevA.102.012224. 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,” Physical Review A, 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.” Physical Review A, vol. 102, no. 1, 012224, American Physical Society, 2020, doi:10.1103/PhysRevA.102.012224. 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 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. Physical Review A. 2019;99(6). doi:10.1103/PhysRevA.99.063627 apa: Karle, V., Defenu, N., & Enss, T. (2019). Coupled superfluidity of binary Bose mixtures in two dimensions. Physical Review A. American Physical Society. https://doi.org/10.1103/PhysRevA.99.063627 chicago: Karle, Volker, Nicolò Defenu, and Tilman Enss. “Coupled Superfluidity of Binary Bose Mixtures in Two Dimensions.” Physical Review A. American Physical Society, 2019. https://doi.org/10.1103/PhysRevA.99.063627. ieee: V. Karle, N. Defenu, and T. Enss, “Coupled superfluidity of binary Bose mixtures in two dimensions,” Physical Review A, 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.” Physical Review A, vol. 99, no. 6, 063627, American Physical Society, 2019, doi:10.1103/PhysRevA.99.063627. 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' ...