Jean-Philippe Brantut

Quantum point contacts in strongly interacting Fermions   

ETH Zürich

In a superfluid or superconductor, strong and non-linear currents can occur as a result of even the smallest perturbation. We present measurement of the non-linear current-bias relation of a strongly interacting Fermi gas at a quantum point contact. The results agree with a theoretical model where the current originates from multiple Andreev reflections. Upon increasing temperature, we observe the disappearance of the non linearity, and the emergence of a linear regime where the conductance significantly departs from predictions based on a Fermi liquid description. By widening the point contact, we observe a competition between superfluidity in the reservoirs and the multimode character of the point contact. This results in non-monotonic conduction properties with varying temperature, with a minimum close to the superfluid transition.