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Observing the drop of resistance in the flow of a superfluid Fermi gas

Abstract

The ability of particles to flow with very low resistance is characteristic of superfluid and superconducting states, leading to their discovery in the past century1,2. Although measuring the particle flow in liquid helium or superconducting materials is essential to identify superfluidity or superconductivity, no analogous measurement has been performed for superfluids based on ultracold Fermi gases. Here we report direct measurements of the conduction properties of strongly interacting fermions, observing the well-known drop in resistance that is associated with the onset of superfluidity. By varying the depth of the trapping potential in a narrow channel connecting two atomic reservoirs, we observed variations of the atomic current over several orders of magnitude. We related the intrinsic conduction properties to the thermodynamic functions in a model-independent way, by making use of high-resolution in situ imaging in combination with current measurements. Our results show that, as in solid-state systems, current and resistance measurements in quantum gases provide a sensitive probe with which to explore many-body physics. Our method is closely analogous to the operation of a solid-state field-effect transistor and could be applied as a probe for optical lattices and disordered systems, paving the way for modelling complex superconducting devices.

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Figure 1: Principle of the experiment.
Figure 2: Conduction properties through the channel.
Figure 3: Density-independent conduction properties through the channel.
Figure 4: Conduction properties as a function of thermodynamic potential.

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Acknowledgements

We acknowledge discussions with W. Zwerger, A. Georges, C. Kollath, C. Grenier, M. Sigrist, G. Blatter and G. Bruun. We thank L. Tarruell, T. Donner and H. Moritz for their careful reading of the manuscript. We acknowledge financing from NCCR MaNEP and QSIT, ERC project SQMS, FP7 project NAME-QUAM and ETHZ. J.-P.B. acknowledges support from EU through a Marie Curie Fellowship.

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Correspondence to Jean-Philippe Brantut or Tilman Esslinger.

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Stadler, D., Krinner, S., Meineke, J. et al. Observing the drop of resistance in the flow of a superfluid Fermi gas. Nature 491, 736–739 (2012). https://doi.org/10.1038/nature11613

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