Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland.
Nature. 2012 Nov 29;491(7426):736-9. doi: 10.1038/nature11613.
The ability of particles to flow with very low resistance is characteristic of superfluid and superconducting states, leading to their discovery in the past century. 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.
粒子以极低阻力流动的能力是超流态和超导态的特征，这导致了它们在上个世纪被发现。尽管测量液体氦或超导材料中的粒子流对于识别超流态或超导性至关重要，但对于基于超冷费米气体的超流态还没有进行类似的测量。在这里，我们报告了对强相互作用费米子的传导性质的直接测量，观察到与超流态开始相关的电阻明显下降。通过在连接两个原子储库的狭窄通道中改变阱深，我们观察到原子电流在几个数量级上的变化。我们通过利用高分辨率原位成像与电流测量相结合，以模型无关的方式将本征传导性质与热力学函数联系起来。我们的结果表明，与固态系统一样，量子气体中的电流和电阻测量提供了一种敏感的探针，可以用来探索多体物理。我们的方法与固态场效应晶体管的操作非常相似，可以应用于光学晶格和无序系统的探针，为复杂超导器件的建模铺平了道路。
