Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Vortices and superfluidity in a strongly interacting Fermi gas

Nature volume 435, pages 1047–1051 (2005)Cite this article

Abstract

Quantum degenerate Fermi gases provide a remarkable opportunity to study strongly interacting fermions. In contrast to other Fermi systems, such as superconductors, neutron stars or the quark-gluon plasma of the early Universe, these gases have low densities and their interactions can be precisely controlled over an enormous range. Previous experiments with Fermi gases have revealed condensation of fermion pairs. Although these and other studies were consistent with predictions assuming superfluidity, proof of superfluid behaviour has been elusive. Here we report observations of vortex lattices in a strongly interacting, rotating Fermi gas that provide definitive evidence for superfluidity. The interaction and therefore the pairing strength between two 6Li fermions near a Feshbach resonance can be controlled by an external magnetic field. This allows us to explore the crossover from a Bose–Einstein condensate of molecules to a Bardeen–Cooper–Schrieffer superfluid of loosely bound pairs. The crossover is associated with a new form of superfluidity that may provide insights into high-transition-temperature superconductors.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Observation of a vortex lattice in a molecular condensate.
Figure 2: Vortices in a strongly interacting gas of fermionic atoms on the BEC- and the BCS-side of the Feshbach resonance.
Figure 3: Optimized vortex lattices in the BEC–BCS crossover.
Figure 4: Vortex number versus magnetic field and interaction strength in the BEC–BCS crossover.
Figure 5: Vortex number versus stirring frequency in the BEC region for different interaction strengths.
Figure 6: Formation and decay of a vortex lattice in a fermion pair condensate on the BEC-side close to the Feshbach resonance.
Figure 7: Decay rate and lifetime of the vortex lattice versus magnetic field and interaction strength.

Similar content being viewed by others

References

  1. Greiner, M., Regal, C. A. & Jin, D. S. Emergence of a molecular Bose–Einstein condensate from a Fermi gas. Nature 426, 537–540 (2003)

    Article  ADS  CAS  Google Scholar 

  2. Jochim, S. et al. Bose-Einstein condensation of molecules. Science 302, 2101–2103 (2003)

    Article  ADS  CAS  Google Scholar 

  3. Zwierlein, M. W. et al. Observation of Bose-Einstein condensation of molecules. Phys. Rev. Lett. 91, 250401 (2003)

    Article  ADS  CAS  Google Scholar 

  4. Regal, C. A., Greiner, M. & Jin, D. S. Observation of resonance condensation of fermionic atom pairs. Phys. Rev. Lett. 92, 040403 (2004)

    Article  ADS  CAS  Google Scholar 

  5. Zwierlein, M. W. et al. Condensation of pairs of fermionic atoms near a Feshbach resonance. Phys. Rev. Lett. 92, 120403 (2004)

    Article  ADS  CAS  Google Scholar 

  6. Bartenstein, M. et al. Crossover from a molecular Bose-Einstein condensate to a degenerate Fermi gas. Phys. Rev. Lett. 92, 120401 (2004)

    Article  ADS  CAS  Google Scholar 

  7. Bourdel, T. et al. Experimental study of the BEC-BCS crossover region in lithium 6. Phys. Rev. Lett. 93, 050401 (2004)

    Article  ADS  CAS  Google Scholar 

  8. Kinast, J., Hemmer, S. L., Gehm, M. E., Turlapov, A. & Thomas, J. E. Evidence for superfluidity in a resonantly interacting Fermi gas. Phys. Rev. Lett. 92, 150402 (2004)

    Article  ADS  CAS  Google Scholar 

  9. Bartenstein, M. et al. Collective excitations of a degenerate gas at the BEC-BCS crossover. Phys. Rev. Lett. 92, 203201 (2004)

    Article  ADS  CAS  Google Scholar 

  10. Chin, C. et al. Observation of the pairing gap in a strongly interacting Fermi gas. Science 305, 1128–1130 (2004)

    Article  ADS  CAS  Google Scholar 

  11. Kinast, J. et al. Heat capacity of a strongly-interacting Fermi gas. Science 307, 1296–1299 (2005)

    Article  ADS  CAS  Google Scholar 

  12. Zwierlein, M. W., Schunck, C. H., Stan, C. A., Raupach, S. M. F. & Ketterle, W. Formation time of a fermion pair condensate. Phys. Rev. Lett. 94, 180401 (2005)

    Article  ADS  CAS  Google Scholar 

  13. Eagles, D. M. Possible pairing without superconductivity at low carrier concentrations in bulk and thin-film superconducting semiconductors. Phys. Rev. 186, 456–463 (1969)

    Article  ADS  CAS  Google Scholar 

  14. Leggett, A. J. in Modern Trends in the Theory of Condensed Matter (eds Pekalski, A. & Przystawa, J.) 13–27 (Proc. XVIth Karpacz Winter School of Theoretical Physics, Springer, Berlin, 1980)

    Book  Google Scholar 

  15. Nozières, P. & Schmitt-Rink, S. Bose condensation in an attractive fermion gas: from weak to strong coupling superconductivity. J. Low Temp. Phys. 59, 195–211 (1985)

    Article  ADS  Google Scholar 

  16. Huang, K. in Bose-Einstein Condensation (eds Griffin, A., Snoke, D. W. & Stringari, S.) 31–50 (Cambridge Univ. Press, Cambridge, 1995)

    Book  Google Scholar 

  17. O'Hara, K. M., Hemmer, S. L., Gehm, M. E., Granade, S. R. & Thomas, J. E. Observation of a strongly interacting degenerate Fermi gas of atoms. Science 298, 2179–2182 (2002)

    Article  ADS  CAS  Google Scholar 

  18. Rodriguez, M., Paraoanu, G.-S. & Törmä, P. Vortices in trapped superfluid Fermi gases. Phys. Rev. Lett. 87, 100402 (2001)

    Article  ADS  CAS  Google Scholar 

  19. Bruun, G. M. & Viverit, L. Vortex state in superfluid trapped Fermi gases at zero temperature. Phys. Rev. A 64, 063606 (2001)

    Article  ADS  Google Scholar 

  20. Pitaevskii, L. & Stringari, S. The quest for superfluidity in Fermi gases. Science 298, 2144–2146 (2002)

    Article  CAS  Google Scholar 

  21. Cozzini, M. & Stringari, S. Fermi gases in slowly rotating traps: superfluid versus collisional hydrodynamics. Phys. Rev. Lett. 91, 070401 (2002)

    Article  Google Scholar 

  22. Bulgac, A. & Yu, Y. Vortex state in a strongly coupled dilute atomic fermionic superfluid. Phys. Rev. Lett. 91, 190404 (2003)

    Article  ADS  Google Scholar 

  23. Schecter, D. A., Dubin, D. H. E., Fine, K. S. & Driscoll, C. F. Vortex crystals from 2D Euler flow: Experiment and simulation. Phys. Fluids 11, 905–914 (1999)

    Article  ADS  CAS  Google Scholar 

  24. Hadzibabic, Z. et al. Fifty-fold improvement in the number of quantum degenerate fermionic atoms. Phys. Rev. Lett. 91, 160401 (2003)

    Article  ADS  CAS  Google Scholar 

  25. Dieckmann, K. et al. Decay of ultracold fermionic lithium gas near a Feshbach resonance. Phys. Rev. Lett. 89, 203201 (2002)

    Article  ADS  CAS  Google Scholar 

  26. Bartenstein, M. et al. Precise determination of 6Li cold collision parameters by radio-frequency spectroscopy on weakly bound molecules. Phys. Rev. Lett. 94, 103201 (2004)

    Article  ADS  Google Scholar 

  27. Matthews, M. R. et al. Vortices in a Bose-Einstein condensate. Phys. Rev. Lett. 83, 2498–2501 (1999)

    Article  ADS  CAS  Google Scholar 

  28. Madison, K. W., Chevy, F., Wohlleben, W. & Dalibard, J. Vortex formation in a stirred Bose-Einstein condensate. Phys. Rev. Lett. 84, 806–809 (2000)

    Article  ADS  CAS  Google Scholar 

  29. Abo-Shaeer, J. R., Raman, C., Vogels, J. M. & Ketterle, W. Observation of vortex lattices in Bose-Einstein condensates. Science 292, 476–479 (2001)

    Article  ADS  CAS  Google Scholar 

  30. Haljan, P. C., Coddington, I., Engels, P. & Cornell, E. A. Driving Bose-Einstein-condensate vorticity with a rotating normal cloud. Phys. Rev. Lett. 87, 210403 (2001)

    Article  ADS  CAS  Google Scholar 

  31. Hodby, E., Hechenblaikner, G., Hopkins, S. A., Maragò, O. M. & Foot, C. J. Vortex nucleation in Bose-Einstein condensates in an oblate, purely magnetic potential. Phys. Rev. Lett. 88, 010405 (2002)

    Article  ADS  CAS  Google Scholar 

  32. Carr, L. D., Shlyapnikov, G. V. & Castin, Y. Achieving a BCS transition in an atomic Fermi gas. Phys. Rev. Lett. 92, 150404 (2004)

    Article  ADS  CAS  Google Scholar 

  33. Onofrio, R. et al. Surface excitations in a Bose-Einstein condensate. Phys. Rev. Lett. 84, 810–813 (2000)

    Article  ADS  CAS  Google Scholar 

  34. Anglin, J. R. Local vortex generation and the surface mode spectrum of large Bose-Einstein condensates. Phys. Rev. Lett. 87, 240401 (2001)

    Article  ADS  CAS  Google Scholar 

  35. Madison, K. W., Chevy, F., Bretin, V. & Dalibard, J. Stationary states of a rotating Bose-Einstein condensate: routes to vortex nucleation. Phys. Rev. Lett. 86, 4443–4446 (2001)

    Article  ADS  CAS  Google Scholar 

  36. Raman, C., Abo-Shaeer, J. R., Vogels, J. M., Xu, K. & Ketterle, W. Vortex nucleation in a stirred Bose-Einstein condensate. Phys. Rev. Lett. 87, 210402 (2001)

    Article  ADS  CAS  Google Scholar 

  37. Madison, K. W., Chevy, F., Wohlleben, W. & Dalibard, J. Vortices in a stirred Bose-Einstein condensate. J. Mod. Opt. 47, 2715–2723 (2000)

    Article  ADS  CAS  Google Scholar 

  38. Abo-Shaeer, J. R., Raman, C. & Ketterle, W. Formation and decay of vortex lattices in Bose-Einstein condensates at finite temperatures. Phys. Rev. Lett. 88, 070409 (2002)

    Article  ADS  CAS  Google Scholar 

  39. Tonini, G. & Castin, Y. Formation of a vortex lattice in a rotating BCS Fermi gas. Preprint at http://arxiv.org/cond-mat/0504612 (2005).

Download references

Acknowledgements

We thank P. Zarth for experimental assistance and C. Stan for contributions in the early stages of the experiment. We also acknowledge discussions with the participants of the OCTS conference in Ohio, and thank J. Anglin, Z. Hadzibabic, D. Kleppner and A. Leanhardt for a critical reading of the manuscript. This work was supported by the NSF, ONR, ARO and NASA.

Author information

Author notes

  1. J. R. Abo-Shaeer

    Present address: Lawrence Berkeley National Laboratory, One Cyclotron Road, MS 88R0192, Berkeley, California, 94720, USA

Authors and Affiliations

  1. Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, MIT, Cambridge, Massachusetts, 02139, USA

    M. W. Zwierlein, J. R. Abo-Shaeer, A. Schirotzek, C. H. Schunck & W. Ketterle

Authors
  1. M. W. Zwierlein
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. J. R. Abo-Shaeer
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. A. Schirotzek
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. C. H. Schunck
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. W. Ketterle
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to M. W. Zwierlein.

Ethics declarations

Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Zwierlein, M., Abo-Shaeer, J., Schirotzek, A. et al. Vortices and superfluidity in a strongly interacting Fermi gas. Nature 435, 1047–1051 (2005). https://doi.org/10.1038/nature03858

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature03858

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing