Abstract
The study of superfluid fermion pairs in a periodic potential has important ramifications for understanding superconductivity in crystalline materials. By using cold atomic gases, various models of condensed matter can be studied in a highly controllable environment. Weakly repulsive fermions in an optical lattice could undergo d-wave pairing1 at low temperatures, a possible mechanism for high temperature superconductivity in the copper oxides2. The lattice potential could also strongly increase the critical temperature for s-wave superfluidity. Recent experimental advances in bulk atomic gases include the observation of fermion-pair condensates and high-temperature superfluidity3,4,5,6,7,8. Experiments with fermions9,10,11 and bosonic bound pairs12,13 in optical lattices have been reported but have not yet addressed superfluid behaviour. Here we report the observation of distinct interference peaks when a condensate of fermionic atom pairs is released from an optical lattice, implying long-range order (a property of a superfluid). Conceptually, this means that s-wave pairing and coherence of fermion pairs have now been established in a lattice potential, in which the transport of atoms occurs by quantum mechanical tunnelling and not by simple propagation. These observations were made for interactions on both sides of a Feshbach resonance. For larger lattice depths, the coherence was lost in a reversible manner, possibly as a result of a transition from superfluid to insulator. Such strongly interacting fermions in an optical lattice can be used to study a new class of hamiltonians with interband and atom–molecule couplings14.
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References
Hofstetter, W., Cirac, J. I., Zoller, P., Demler, E. & Lukin, M. D. High-temperature superfluidity of fermionic atoms in optical lattices. Phys. Rev. Lett. 89, 220407 (2002)
Scalapino, D. J. The case for \(d_{x^2 - y^2 } \)pairing in the cuprate superconductors. Phys. Rep. 250, 329–365 (1995)
Greiner, M., Regal, C. A. & Jin, D. S. Emergence of a molecular Bose–Einstein condensate from a Fermi gas. Nature 426, 537–540 (2003)
Jochim, S. et al. Bose–Einstein condensation of molecules. Science 302, 2101–2103 (2003)
Zwierlein, M. W. et al. Observation of Bose–Einstein condensation of molecules. Phys. Rev. Lett. 91, 250401 (2003)
Regal, C. A., Greiner, M. & Jin, D. S. Observation of resonance condensation of fermionic atom pairs. Phys. Rev. Lett. 92, 040403 (2004)
Zwierlein, M. W. et al. Condensation of pairs of fermionic atoms near a Feshbach resonance. Phys. Rev. Lett. 92, 120403 (2004)
Zwierlein, M. W., Abo-Shaeer, J. R., Schirotzek, A., Schunck, C. H. & Ketterle, W. Vortices and superfluidity in a strongly interacting Fermi gas. Nature 435, 1047–1051 (2005)
Modugno, G., Ferlaino, F., Heidemann, R., Roati, G. & Inguscio, M. Production of a Fermi gas of atoms in an optical lattice. Phys. Rev. A 68, 011601(R) (2003)
Köhl, M., Moritz, H., Stöferle, T., Gunther, K. & Esslinger, T. Fermionic atoms in a three-dimensional optical lattice: observing Fermi surfaces, dynamics, and interactions. Phys. Rev. Lett. 94, 080403 (2005)
Stöferle, T., Moritz, H., Gunther, K., Kohl, M. & Esslinger, T. Molecules of fermionic atoms in an optical lattice. Phys. Rev. Lett. 96, 030401 (2006)
Volz, T. et al. A Mott state of molecules. Condensed Matt. (submitted); preprint at <http://arxiv.org/abs/cond-mat/0605184> (2006)
Winkler, K. et al. Repulsively bound atom pairs in an optical lattice. Nature 441, 853–856 (2006)
Duan, L-M. Effective Hamiltonian for Fermions in an optical lattice across a Feshbach resonance. Phys. Rev. Lett. 95, 243202 (2005)
Andrews, M. R. et al. Observation of interference between two Bose condensates. Science 275, 637–641 (1997)
Madison, K. W., Chevy, F., Wohlleben, W. & Dalibard, J. Vortex formation in a stirred Bose–Einstein condensate. Phys. Rev. Lett. 84, 806–809 (2000)
Abo-Shaeer, J. R., Raman, C., Vogels, J. M. & Ketterle, W. Observation of vortex lattices in Bose–Einstein condensates. Science 292, 476–479 (2001)
Anderson, B. P. & Kasevich, M. A. Macroscopic quantum interference from atomic tunnel arrays. Science 282, 1686–1689 (1998)
Greiner, M., Mandel, O., Esslinger, T., Hänsch, T. W. & Bloch, I. Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms. Nature 415, 39–44 (2002)
Schunck, C., Zwierlein, M. W., Schirotzek, A. & Ketterle, W. Superfluid expansion of a strongly interacting Fermi gas. Condensed Matt. (submitted); preprint at <http://arxiv.org/abs/cond-mat/0607298> (2006)
Onofrio, R. et al. Observation of superfluid flow in a Bose–Einstein condensed gas. Phys. Rev. Lett. 85, 2228–2231 (2000)
Schori, C., Stöferle, T., Moritz, H., Köhl, M. & Esslinger, T. Excitations of a superfluid in a three-dimensional optical lattice. Phys. Rev. Lett. 93, 240402 (2004)
Xu, K. et al. Sodium Bose–Einstein condensates in an optical lattice. Phys. Rev. A. 72, 043604 (2005)
Moritz, H., Stöferle, T., Gunter, K., Köhl, M. & Esslinger, T. Confinement induced molecules in a 1d Fermi gas. Phys. Rev. Lett. 94, 210401 (2005)
Koetsier, A. O., Dickerscheid, D. B. M. & Stoof, H. T. C. BEC–BCS crossover in an optical lattice. Condensed Matt. (submitted); preprint at <http://arxiv.org/abs/cond-mat/0604186> (2006)
Gubbels, K. B., Dickerscheid, D. B. M. & Stoof, H. T. C. Dressed molecules in an optical lattice. Condensed Matt. (submitted); preprint at <http://arxiv.org/abs/cond-mat/0605056> (2006)
Hadzibabic, Z. et al. Fifty-fold improvement in the number of quantum degenerate fermionic atoms. Phys. Rev. Lett. 91, 160401 (2003)
Stan, C. A. & Ketterle, W. Multiple species atom source for laser-cooling experiments. Rev. Sci. Instrum. 76, 063113 (2005)
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)
Gould, P. L., Ruff, G. A. & Pritchard, D. E. Diffraction of atoms by light: the near-resonant Kapitza–Dirac effect. Phys. Rev. Lett. 56, 827–830 (1986)
Acknowledgements
We thank E. Demler, Z. Hadzibabic and M. Zwierlein for discussions. This work was supported by the NSF, the Office of Naval Research and NASA.
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Chin, J., Miller, D., Liu, Y. et al. Evidence for superfluidity of ultracold fermions in an optical lattice. Nature 443, 961–964 (2006). https://doi.org/10.1038/nature05224
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DOI: https://doi.org/10.1038/nature05224
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