Letter | Published:

Observation of quantized conductance in neutral matter

Nature volume 517, pages 6467 (01 January 2015) | Download Citation

Abstract

In transport experiments, the quantum nature of matter becomes directly evident when changes in conductance occur only in discrete steps1, with a size determined solely by Planck’s constant h. Observations of quantized steps in electrical conductance2,3 have provided important insights into the physics of mesoscopic systems4 and have allowed the development of quantum electronic devices5. Even though quantized conductance should not rely on the presence of electric charges, it has never been observed for neutral, massive particles6. In its most fundamental form, it requires a quantum-degenerate Fermi gas, a ballistic and adiabatic transport channel, and a constriction with dimensions comparable to the Fermi wavelength. Here we report the observation of quantized conductance in the transport of neutral atoms driven by a chemical potential bias. The atoms are in an ultraballistic regime, where their mean free path exceeds not only the size of the transport channel, but also the size of the entire system, including the atom reservoirs. We use high-resolution lithography to shape light potentials that realize either a quantum point contact or a quantum wire for atoms. These constrictions are imprinted on a quasi-two-dimensional ballistic channel connecting the reservoirs7. By varying either a gate potential or the transverse confinement of the constrictions, we observe distinct plateaux in the atom conductance. The conductance in the first plateau is found to be equal to the universal conductance quantum, 1/h. We use Landauer’s formula to model our results and find good agreement for low gate potentials, with all parameters determined a priori. Our experiment lets us investigate quantum conductors with wide control not only over the channel geometry, but also over the reservoir properties, such as interaction strength, size and thermalization rate.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1.

    in Directions in Condensed Matter (eds & ) 120–145 (World Scientific, 1986)

  2. 2.

    et al. Quantized conductance of point contacts in a two-dimensional electron gas. Phys. Rev. Lett. 60, 848–850 (1988)

  3. 3.

    et al. One-dimensional transport and the quantisation of the ballistic resistance. J. Phys. C 21, L209 (1988)

  4. 4.

    Introduction to Mesoscopic Physics (Oxford Univ. Press, 2002)

  5. 5.

    Semiconductor Nanostructures (Oxford Univ. Press, 2010)

  6. 6.

    , & On the feasibility of detecting quantized conductance in neutral matter. J. Low Temp. Phys. 141, 99–109 (2005)

  7. 7.

    , , , & Conduction of ultracold fermions through a mesoscopic channel. Science 337, 1069–1071 (2012)

  8. 8.

    Spatial variation of currents and fields due to localized scatterers in metallic conduction. IBM J. Res. Develop. 1, 223–231 (1957)

  9. 9.

    , , & Generalized many-channel conductance formula with application to small rings. Phys. Rev. B 31, 6207–6215 (1985)

  10. 10.

    , , , & The signature of conductance quantization in metallic point contacts. Nature 375, 767–769 (1995)

  11. 11.

    , , & Carbon nanotube quantum resistors. Science 280, 1744–1746 (1998)

  12. 12.

    , & Quantum point contacts for neutral atoms. Phys. Rev. Lett. 83, 3762–3765 (1999)

  13. 13.

    et al. Realization of Bose-Einstein condensates in lower dimensions. Phys. Rev. Lett. 87, 130402 (2001)

  14. 14.

    , , & Exciting collective oscillations in a trapped 1D gas. Phys. Rev. Lett. 91, 250402 (2003)

  15. 15.

    et al. Tonks–Girardeau gas of ultracold atoms in an optical lattice. Nature 429, 277–281 (2004)

  16. 16.

    , & Observation of a one-dimensional Tonks-Girardeau gas. Science 305, 1125–1128 (2004)

  17. 17.

    , & in Atom Chips (eds & ) 331–363 (Wiley, 2010)

  18. 18.

    et al. Deterministic preparation of a tunable few-fermion system. Science 332, 336–338 (2011)

  19. 19.

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

  20. 20.

    , , , & Observing the drop of resistance in the flow of a superfluid Fermi gas. Nature 491, 736–739 (2012)

  21. 21.

    , , , & Superfluidity with disorder in a thin film of quantum gas. Phys. Rev. Lett. 110, 100601 (2013)

  22. 22.

    & Quantum point contacts. Phys. Today 49, 22–27 (1996)

  23. 23.

    , , , & High-resolution imaging of ultracold fermions in microscopically tailored optical potentials. New J. Phys. 13, 043007 (2011)

  24. 24.

    & & Reflectionless quantum transport and fundamental ballistic-resistance steps in microscopic constrictions. JETP Lett. 48, 238–241 (1988)

  25. 25.

    et al. Nonlinear conductance of quantum point contacts. Phys. Rev. B 39, 8040–8043 (1989)

  26. 26.

    & Where is the potential drop in a quantum point contact? Superlattices Microstruct. 23, 719–730 (1998)

  27. 27.

    & Theory of quantum conduction through a constriction. Phys. Rev. Lett. 62, 300–303 (1989)

  28. 28.

    & Quantization of the conductance of ballistic point contacts beyond the adiabatic approximation. Phys. Rev. B 41, 5341–5350 (1990)

  29. 29.

    & Incompleteness of the Landauer formula for electronic transport. Phys. Rev. B 79, 014201 (2009)

  30. 30.

    & Topological insulators. Rev. Mod. Phys. 82, 3045–3067 (2010)

  31. 31.

    Quantum Phase Transitions 260–290 (Cambridge Univ. Press, 2011)

  32. 32.

    & Universal conductance fluctuations in metals. Phys. Rev. Lett. 55, 1622 (1985)

  33. 33.

    et al. A thermoelectric heat engine with ultracold atoms. Science 342, 713–715 (2013)

  34. 34.

    , , & Accelerating evaporative cooling of atoms into Bose-Einstein condensation in optical traps. Phys. Rev. A 78, 011604 (2008)

  35. 35.

    , , & Quantum-statistics-induced flow patterns in driven ideal Fermi gases. Phys. Rev. A 88, 043611 (2013)

  36. 36.

    , , & Exploring classically chaotic potentials with a matter wave quantum probe. Phys. Rev. Lett. 107, 254104 (2011)

  37. 37.

    , , & Scaling laws for evaporative cooling in time-dependent optical traps. Phys. Rev. A 64, 051403 (2001)

  38. 38.

    , & Inelastic collisions of a fermi gas in the BEC-BCS crossover. Phys. Rev. Lett. 102, 250402 (2009)

  39. 39.

    et al. Precise characterization of Li6 Feshbach resonances using trap-sideband-resolved RF spectroscopy of weakly bound molecules. Phys. Rev. Lett. 110, 135301 (2013)

  40. 40.

    Qualitative Methods in Quantum Theory 115–118 (Perseus, 2000)

  41. 41.

    Role of quantum coherence in series resistors. Phys. Rev. B 33, 3020–3026 (1986)

  42. 42.

    Transport Durch Ballistische Leiter 44–52, PhD thesis, LMU München. (1997)

Download references

Acknowledgements

We acknowledge discussions with G. Blatter, K. Ensslin, C. Glattli, T. Giamarchi, C. Grenier and M. Lebrat, and thank C. Chin, T. Ihn, Y. Imry, and W. Zwerger for their careful reading of the manuscript and for discussions. We acknowledge financing from NCCR QSIT, the ERC Project SQMS, the FP7 project SIQS and ETHZ. J.-P.B. is supported by the Ambizione program of SNF.

Author information

Affiliations

  1. Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland

    • Sebastian Krinner
    • , David Stadler
    • , Dominik Husmann
    • , Jean-Philippe Brantut
    •  & Tilman Esslinger

Authors

  1. Search for Sebastian Krinner in:

  2. Search for David Stadler in:

  3. Search for Dominik Husmann in:

  4. Search for Jean-Philippe Brantut in:

  5. Search for Tilman Esslinger in:

Contributions

All authors contributed equally to this work.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Jean-Philippe Brantut.

Extended data

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/nature14049

Further reading

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.