Heidelberg 2015 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 4: Quantum Gases: Fermions I

Q 4.3: Talk

Monday, March 23, 2015, 12:00–12:15, K/HS2

Non-linear superflow of strongly interacting Fermions in a quantum point contact — •Dominik Husmann¹, Sebastian Krinner¹, Martin Lebrat¹, Jean-Philippe Brantut¹, Shun Uchino², Thierry Giamarchi², and Tilman Esslinger¹ — ¹Institut für Quantenelektronik, ETH Zürich, Schweiz — ²Department of Quantum Matter Physics, University of Geneva, Schweiz

Superfluids, like superconductors, are characterised by their strong, non-linear response to a bias. Here we report on the measurement of the non-linear current-bias relation of a strongly interacting Fermi gas flowing through a narrow constriction. We prepare a cigar-shaped cloud of ultracold ⁶Li close to a Feshbach resonance where the scattering length diverges and the system behaves as a unitary Fermi gas. The cloud is then narrowed down in the center by means of repulsive laser beams, creating a system of two separate clouds connected by a one-dimensional constriction, a quantum point contact (QPC). By imposing a chemical potential bias between the two clouds and observing the dynamics of particle flow, we analyse the current-bias characteristics of our system and find nonlinear behaviour indicating superfluid behaviour. The results agree quantitatively with a biased superfluid point contact model treated with the Keldysh formalism, suggesting that the supercurrent originates from multiple Andreev reflections. We study the influence the density in the QPC and investigate the effect of finite temperature effects on the current-bias characteristics.