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  • Letter
  • Open Access

Confinement and finite-range effects in a quasi-two-dimensional gas of fermionic dimers

Giovanni Midei1,2,3, Jordi Boronat1, and Grigory E. Astrakharchik1,*

  • *Contact author: grigori.astrakharchik@upc.edu
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Phys. Rev. Research 8, L022051 – Published 17 June, 2026

DOI: https://doi.org/10.1103/lr46-r6wg

Abstract

We investigate the ground-state properties of ultracold two-component Fermi gases in the presence of a transverse harmonic potential, focusing on the strongly interacting regime in which pairs of fermions form tightly bound molecules. Using the fixed-node diffusion Monte Carlo method, we calculate the equation of state and density profiles for the full fermionic system, which allows us to address the importance of finite-range corrections arising from the internal fermionic structure of the dimers. We interpret the results in terms of a molecular Bose gas in quasi-two-dimensional confinement and compare them with theoretical predictions for a weakly interacting two-dimensional Bose gas, identifying the range of validity of mean-field and beyond-mean-field descriptions. We also develop an analytical theory for the transverse density profile, capturing its broadening with increasing interaction strength. This work provides a benchmark for an effective bosonic description of strongly bound fermionic dimers and offers insights into confinement-induced dimensional effects.

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References (33)

  1. T. Köhler, K. Góral, and P. S. Julienne, Production of cold molecules via magnetically tunable Feshbach resonances, Rev. Mod. Phys. 78, 1311 (2006).
  2. C. Chin, R. Grimm, P. S. Julienne, and E. Tiesinga, Feshbach resonances in ultracold gases, Rev. Mod. Phys. 82, 1225 (2010).
  3. D. S. Petrov, C. Salomon, and G. V. Shlyapnikov, Weakly bound dimers of fermionic atoms, Phys. Rev. Lett. 93, 090404 (2004).
  4. C. A. Regal, C. Ticknor, J. L. Bohn, and D. S. Jin, Creation of ultracold molecules from a Fermi gas of atoms, Nature (London) 424, 47 (2003).
  5. K. E. Strecker, G. B. Partridge, and R. G. Hulet, Conversion of an atomic Fermi gas to a long-lived molecular Bose gas, Phys. Rev. Lett. 91, 080406 (2003).
  6. J. Cubizolles, T. Bourdel, S. J. J. M. F. Kokkelmans, G. V. Shlyapnikov, and C. Salomon, Production of long-lived ultracold Li2 molecules from a Fermi gas, Phys. Rev. Lett. 91, 240401 (2003).
  7. S. Jochim, M. Bartenstein, A. Altmeyer, G. Hendl, C. Chin, J. H. Denschlag, and R. Grimm, Pure gas of optically trapped molecules created from fermionic atoms, Phys. Rev. Lett. 91, 240402 (2003).
  8. S. Jochim, M. Bartenstein, A. Altmeyer, G. Hendl, S. Riedl, C. Chin, J. H. Denschlag, and R. Grimm, Bose–Einstein condensation of molecules, Science 302, 2101 (2003).
  9. M. Greiner, C. A. Regal, and D. S. Jin, Emergence of a molecular Bose–Einstein condensate from a Fermi gas, Nature (London) 426, 537 (2003).
  10. M. W. Zwierlein, C. A. Stan, C. H. Schunck, S. M. F. Raupach, S. Gupta, Z. Hadzibabic, and W. Ketterle, Observation of Bose–Einstein condensation of molecules, Phys. Rev. Lett. 91, 250401 (2003).
  11. C. A. Regal, M. Greiner, and D. S. Jin, Observation of resonance condensation of fermionic atom pairs, Phys. Rev. Lett. 92, 040403 (2004).
  12. M. W. Zwierlein, J. R. Abo-Shaeer, A. Schirotzek, C. H. Schunck, and W. Ketterle, Vortices and superfluidity in a strongly interacting Fermi gas, Nature (London) 435, 1047 (2005).
  13. The BCS–BEC Crossover and the Unitary Fermi Gas, edited by W. Zwerger (Springer, Berlin, 2012).
  14. G. C. Strinati, P. Pieri, G. Röpke, P. Schuck, and M. Urban, The BCS–BEC crossover: From ultracold Fermi gases to nuclear systems, Phys. Rep. 738, 1 (2018).
  15. A. Perali, P. Pieri, and G. C. Strinati, Quantitative comparison between theoretical predictions and experimental results for the BCS-BEC crossover, Phys. Rev. Lett. 93, 100404 (2004).
  16. J. P. Gaebler, J. T. Stewart, T. E. Drake, D. S. Jin, A. Perali, P. Pieri, and G. C. Strinati, Observation of pseudogap behaviour in a strongly interacting Fermi gas, Nat. Phys. 6, 569 (2010).
  17. A. Perali, F. Palestini, P. Pieri, G. C. Strinati, J. T. Stewart, J. P. Gaebler, T. E. Drake, and D. S. Jin, Evolution of the normal state of a strongly interacting Fermi gas from a pseudogap phase to a molecular Bose gas, Phys. Rev. Lett. 106, 060402 (2011).
  18. F. Marsiglio, P. Pieri, A. Perali, F. Palestini, and G. C. Strinati, Pairing effects in the normal phase of a two-dimensional Fermi gas, Phys. Rev. B 91, 054509 (2015).
  19. S. Pilati, J. Boronat, J. Casulleras, and S. Giorgini, Quantum Monte Carlo simulation of a two-dimensional Bose gas, Phys. Rev. A 71, 023605 (2005).
  20. V. A. Yurovsky, A. Ben-Reuven, P. S. Julienne, and C. J. Williams, Atom loss from Bose–Einstein condensates due to Feshbach resonance, Phys. Rev. A 60, R765 (1999).
  21. R. Henke, J. Levinsen, M. M. Parish, J. Boronat, G. E. Astrakharchik, H. Moritz, and C. R. Cabrera, Realization of repulsive polarons in the strongly correlated regime, arXiv:2511.03569.
  22. G. Bertaina and S. Giorgini, BCS–BEC crossover in a two-dimensional Fermi gas, Phys. Rev. Lett. 106, 110403 (2011).
  23. G. E. Astrakharchik, J. Boronat, J. Casulleras, and S. Giorgini, Equation of state of a Fermi gas in the BEC–BCS crossover: A quantum Monte Carlo study, Phys. Rev. Lett. 93, 200404 (2004).
  24. J. B. Anderson, A random-walk simulation of the Schrödinger equation: H3+, J. Chem. Phys. 63, 1499 (1975).
  25. J. B. Anderson, Quantum chemistry by random walk: Higher accuracy, J. Chem. Phys. 73, 3897 (1980).
  26. P. J. Reynolds, D. M. Ceperley, B. J. Alder, and W. A. J. Lester, Fixed-node quantum Monte Carlo for molecules, J. Chem. Phys. 77, 5593 (1982).
  27. Y. Castin, Condensats de Bose-Einstein Tome 2: La Théorie, des Fondements aux Applications Tome 2 (EDP Sciences, Les Ulis, 2025).
  28. T. Kirk and M. M. Parish, Three-body correlations in a two-dimensional SU(3) Fermi gas, Phys. Rev. A 96, 053614 (2017).
  29. A. Deltuva, Universality in fermionic dimer–dimer scattering, Phys. Rev. A 96, 022701 (2017).
  30. E. Braaten, H.-W. Hammer, and S. Hermans, Nonuniversal effects in the homogeneous Bose gas, Phys. Rev. A 63, 063609 (2001).
  31. J. Pera and J. Boronat, Low-energy scattering parameters: A theoretical derivation of the effective range and scattering length for arbitrary angular momentum, Am. J. Phys. 91, 90 (2023).
  32. G. E. Astrakharchik, J. Boronat, J. Casulleras, I. L. Kurbakov, and Y. E. Lozovik, Equation of state of a weakly interacting two-dimensional Bose gas studied at zero temperature by means of quantum Monte Carlo methods, Phys. Rev. A 79, 051602(R) (2009).
  33. K. Merloti, R. Dubessy, L. Longchambon, M. Olshanii, and H. Perrin, Breakdown of scale invariance in a quasi-two-dimensional Bose gas due to the presence of the third dimension, Phys. Rev. A 88, 061603(R) (2013).

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Phys. Rev. Research 8, L022051– Published 17 June, 2026
  • Received 18 December 2025
  • Accepted 20 May 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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