2015/11/30 by Sebastian Krinner, Martin Lebrat, Dominik Husmann +3 · 1 citation
Mathematics · Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Geology #Geometry #Materials science #Mathematics #Particle (ecology) #Physics #Point (geometry) #Quantum #Quantum and electron transport phenomena #Quantum mechanics #Quantum point contact #Quantum well #Quantum, superfluid, helium dynamics #Spin (aerodynamics) #Statistical physics #Thermodynamics #cond-mat.mes-hall #cond-mat.quant-gas
paper · pdf · doi:10.1073/pnas.1601812113
14 pages, 8 figures
arxiv created 2016/05/26 · openalex publication_date 2016/06/29 · arxiv updated 2016/09/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study particle and spin transport in a single-mode quantum point contact, using a charge neutral, quantum degenerate Fermi gas with tunable, attractive interactions. This yields the spin and particle conductance of the point contact as a function of chemical potential or confinement. The measurements cover a regime from weak attraction, where quantized conductance is observed, to the resonantly interacting superfluid. Spin conductance exhibits a broad maximum when varying the chemical potential at moderate interactions, which signals the emergence of Cooper pairing. In contrast, the particle conductance is unexpectedly enhanced even before the gas is expected to turn into a superfluid, continuously rising from the plateau at [Formula: see text] for weak interactions to plateau-like features at nonuniversal values as high as [Formula: see text] for intermediate interactions. For strong interactions, the particle conductance plateaus disappear and the spin conductance gets suppressed, confirming the spin-insulating character of a superfluid. Our observations document the breakdown of universal conductance quantization as many-body correlations appear. The observed anomalous quantization challenges a Fermi liquid description of the normal phase, shedding new light on the nature of the strongly attractive Fermi gas.