Hannover 2016 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 53: Quantum Gases: Fermions I

Q 53.4: Talk

Thursday, March 3, 2016, 15:15–15:30, e001

Spin transport of ultracold fermions through a quantum point contact — •Martin Lebrat¹, Sebastian Krinner¹, Dominik Husmann¹, Samuel Häusler¹, Charles Grenier², Jean-Philippe Brantut¹, and Tilman Esslinger¹ — ¹Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland — ²Laboratoire de Physique, ENS de Lyon, 69364 Lyon, France

We report on the first measurement of spin conductance through a quantum point contact (QPC) with ultracold fermions. Experimentally, we prepare two clouds of ⁶Li atoms with opposite populations in two different hyperfine states, connect them by a narrow, optically-shaped constriction, and monitor the atomic flow in a spin-resolved way to infer spin conductance. In absence of interactions, conductance is expected to reach a quantum of 1/h whenever the Fermi wavelength is comparable to the transverse dimensions of the constriction.

As attractive interactions are increased towards the BEC-BCS crossover, we observe a non-monotonic behaviour of the spin conductance as a function of atomic density around the QPC, which is consistent with the appearance of a superfluid gap. For weaker interactions in the normal phase, we measure a reduction of conductance from the conductance quantum 1/h, that can be attributed to one-dimensional scattering within the QPC between excitations of opposite spins.