Letter | Published:

The a.c. and d.c. Josephson effects in a Bose–Einstein condensate

Nature volume 449, pages 579583 (04 October 2007) | Download Citation

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Abstract

The alternating- and direct-current (a.c. and d.c.) Josephson effects were first discovered in a system of two superconductors, the macroscopic wavefunctions of which are weakly coupled via a tunnelling barrier1,2. In the a.c. Josephson effect1,2,3,4,5,6,7, a constant chemical potential difference (voltage) is applied, which causes an oscillating current to flow through the barrier. Because the frequency is proportional to the chemical potential difference only, the a.c. Josephson effect serves as a voltage standard2. In the d.c. Josephson effect, a small constant current is applied, resulting in a constant supercurrent flowing through the barrier4,5,8. In a sense, the particles do not ‘feel’ the presence of the tall tunnelling barrier, and flow freely through it with no driving potential. Bose–Einstein condensates should also support Josephson effects9; however, while plasma oscillations have been seen10 in a single Bose–Einstein condensate Josephson junction, the a.c. Josephson effect remains elusive. Here we observe the a.c. and d.c. Josephson effects in a single Bose–Einstein condensate Josephson junction. The d.c. Josephson effect has been observed previously only in superconducting systems11; in our study, it is evident when we measure the chemical potential–current relation of the Bose–Einstein condensate Josephson junction4,11. Our system constitutes a trapped-atom interferometer12,13 with continuous readout14, which operates on the basis of the a.c. Josephson effect. In addition, the measured chemical potential–current relation shows that the device is suitable for use as an analogue of the superconducting quantum interference device, which would sense rotation2,15.

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Change history

  • 05 October 2007

    On 5 October 2007 Figs 3 and 4 were replaced online with higher resolution versions to match more closely the print resolution.

References

  1. 1.

    Possible new effects in superconductive tunnelling. Phys. Lett. 1, 251–253 (1962)

  2. 2.

    & Physics and Applications of the Josephson Effect Chs 1, 6, 11 13 (Wiley, New York, 1982)

  3. 3.

    , & Order parameter at the boundary of a trapped Bose gas. Phys. Rev. A. 54, 4213–4217 (1996)

  4. 4.

    , & Josephson effects in dilute Bose-Einstein condensates. Phys. Rev. Lett. 84, 4521–4524 (2000)

  5. 5.

    & Josephson tunneling between weakly interacting Bose-Einstein condensates. Phys. Rev. A. 64, 033610 (2001)

  6. 6.

    , , & Coherent oscillations between two weakly-coupled Bose-Einstein condensates: Josephson effects, π oscillations, and macroscopic quantum self-trapping. Phys. Rev. A. 59, 620–633 (1999)

  7. 7.

    , , & Quantum coherent atomic tunneling between two trapped Bose-Einstein condensates. Phys. Rev. Lett. 79, 4950–4953 (1997)

  8. 8.

    , , & Josephson spectroscopy of a dilute Bose-Einstein condensate in a double-well potential. Phys. Rev. A 66, 033612 (2002)

  9. 9.

    Oscillatory exchange of atoms between traps containing Bose condensates. Phys. Rev. Lett. 57, 3164–3166 (1986)

  10. 10.

    et al. Direct observation of tunneling and nonlinear self-trapping in a single Bosonic Josephson junction. Phys. Rev. Lett. 95, 010402 (2005)

  11. 11.

    & Probable observation of the Josephson superconducting tunneling effect. Phys. Rev. Lett. 10, 230–232 (1963)

  12. 12.

    et al. Atom interferometry with Bose-Einstein condensates in a double-well potential. Phys. Rev. Lett. 92, 050405 (2001)

  13. 13.

    et al. Matter-wave interferometry in a double well on an atom chip. Nature Phys. 1, 57–62 (2005)

  14. 14.

    et al. Light scattering to determine the relative phase of two Bose-Einstein condensates. Science 307, 1945–1948 (2005)

  15. 15.

    & Principles of superfluid-helium gyroscopes. Phys. Rev. B 46, 3540–3549 (1992)

  16. 16.

    , , & Theory of Bose-Einstein condensation in trapped gases. Rev. Mod. Phys. 71, 463–512 (1999)

  17. 17.

    , & Josephson effect between trapped Bose-Einstein condensates. Phys. Rev. A. 57, R28–R31 (1998)

  18. 18.

    , , , & Bose-condensate tunneling dynamics: momentum-shortened pendulum with damping. Phys. Rev. A. 60, 487–493 (1999)

  19. 19.

    Bose-Einstein condensation in the alkali gases: some fundamental concepts. Rev. Mod. Phys. 73, 307–356 (2001)

  20. 20.

    , & The Feynman Lectures on Physics Vol. 3, Ch. 21 (Addison-Wesley, Reading, Massachusetts, 1965)

  21. 21.

    Dynamics of Josephson Junctions and Circuits Chs 1, 3 5 (Gordon and Breach Science Publishers, New York, 1986)

  22. 22.

    et al. Josephson junction arrays with Bose-Einstein condensates. Science 293, 843–846 (2001)

  23. 23.

    , , , & Quantum oscillations between two weakly coupled reservoirs of superfluid 3He. Nature 388, 449–451 (1997)

  24. 24.

    & Macroscopic quantum interference from atomic tunnel arrays. Science 282, 1686–1689 (1998)

  25. 25.

    , , & Measurements of relative phase in two-component Bose-Einstein condensates. Phys. Rev. Lett. 81, 1543–1546 (1998)

  26. 26.

    , , & Magnetic transport of trapped cold atoms over a large distance. Phys. Rev. A 63, 031401(R) (2001)

  27. 27.

    & Bose-Einstein condensate in a double-well potential as an open quantum system. Phys. Rev. A 58, R50–R53 (1998)

  28. 28.

    & Thermal versus quantum decoherence in double well trapped Bose-Einstein condensates. Phys. Rev. Lett. 87, 180402 (2001)

  29. 29.

    , , , & Quantum interference of superfluid 3He. Nature 412, 55–58 (2001)

  30. 30.

    , & Precision rotation measurements with an atom interferometer gyroscope. Phys. Rev. Lett. 78, 2046–2049 (1997)

  31. 31.

    , & Bose-Einstein condensation in a quadrupole-Ioffe configuration trap. Phys. Rev. A. 58, R2664–R2667 (1998)

  32. 32.

    et al. Direct, nondestructive observation of a Bose condensate. Science 273, 84–87 (1996)

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Acknowledgements

We thank W. Ketterle, M. Segev, E. Altman, Y. Kafri, E. Akkermans, E. Polturak, B. Shapiro and R. Pugatch for readings of the manuscript. This work was supported by the Israel Science Foundation and the Russell Berrie Nanotechnology Institute.

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Affiliations

  1. Department of Physics, Technion—Israel Institute of Technology, Technion City, Haifa 32000, Israel

    • S. Levy
    • , E. Lahoud
    • , I. Shomroni
    •  & J. Steinhauer

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Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to J. Steinhauer.

Supplementary information

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    Supplementary Information

    The file contains Supplementary Figure 1, Supplementary Discussion and Supplementary Notes. The supplementary information gives additional details of the experimental system. Furthermore, the calibration of the experiment is discussed. Also, explicit definitions from the two-state model are given, as well as an approximate calculation of the conductance. We calculate the energy of an analogous superconducting circuit. The sensitivity of a BEC SQUID is given.

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https://doi.org/10.1038/nature06186

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