Mainz 2017 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 40: Poster: Quantum Optics and Photonics II
Q 40.10: Poster
Wednesday, March 8, 2017, 17:00–19:00, P OG2
Measuring transport properties of a quantum point contact for cold atoms — •Dominik Husmann1, Martin Lebrat1, Samuel Häusler1, Sebastian Krinner1, Laura Corman1, Jean-Philippe Brantut2, and Tilman Esslinger1 — 1Institute for Quantum Electronics, ETH Zurich, Switzerland — 2Institute of Physics, EPFL Lausanne, Switzerland
Quantum point contacts (QPCs) featuring quantization of conductance are fundamental components for mesoscopic nanostructures. Here we study the evolution of quantized conductance with interaction strength across the BEC-BCS crossover in ultracold fermions. Our system is a two-terminal setup of lithium 6 atoms in two different hyperfine states, connected by an optically tailored QPC. We impose independently a spin or particle imbalance between the reservoirs, creating a restoring drive that allows to measure spin and particle conductance. With increasing attractive interactions we find a plateau in the particle conductance at values larger than the expected quantum of 1/h. Subsequently we observe an onset of superfluidity manifested in a abrupt increase of the conductance with density. The superfluid gap causes a suppression of spin excitations, which we see in a non-monotonous behavior in spin conductance as a function of density. Complementary to creating particle and spin bias, we can apply a temperature gradient between the reservoirs. The thermoelectric response of the system is an interplay between QPC and reservoir contributions. The high tunability of our system opens up a wide parameter range to study thermoelectricity through a QPC.