Day / Time
Date(s) - 10/03/2015
13 h 00 min - 14 h 00 min
Mardi 10 mars, 2015, 13 h 00
Auditoire Stückelberg, Ecole de physique
Dr. Jean-Philippe Brantut
Institute forQuantum Electronics – Quantum optics group
Mesoscopic physics experiments with neutral atoms
In transport experiments the quantum nature of matter becomes directly evident when changes in conductance occur only in discrete steps, with a size determined solely by Planck’s constant h. I will present the first observation of quantized conductance in the transport of neutral particles. I will describe our experimental techniques, that allow to optically imprint a quantum point contact for atoms, onto a quasi two-dimensional ballistic channel connecting two reservoirs of quantum degenerate Lithium atoms. By tuning either a gate potential or the transverse confinement of the constrictions, we observe distinct plateaus in the conductance for atoms. The conductance in the first plateau is found to be equal to 1/h, the universal conductance quantum for neutral matter. For low gate potentials we find good agreement between the experimental data and the Landauer formula, with all parameters determined a priori.
I will then show recent results that make use of the unique opportunity offered by cold atom systems to control the interactions between particles. We have observed the progressive disappearance of quantized conductance as attractive interactions are raised. For unitary limited interactions, the system features a strongly non linear current-bias characteristic, related to the superfluid nature of the gas. The results are compared with a non-equilibrium mean-field theory, with quantitative agreement at low temperature.