Yefsah, Tarik

Date:    Monday, September 10, 2018
Time:   16:00
Place:   École Polytechnique Fédérale de Lausanne – PH H3 31
Host:    Jean-Philippe Brantut

Probing Local Correlations in a Unitary Fermi Gas

Tarik Yefsah
École Normale Supérieure, Paris, France

We will present a measurement of local correlations in a Unitary Fermi gas, where immersed Bose impurities are used as a probe. We will first show that the three-body recombination rate in a Bose-Fermi mixture can be quantitatively related to the Contact of the Unitary gas. Second, I will present our measurements on a 7Li/6Li mixture, where we probe the recombination rate in both the thermal and dual superfluid regimes. At unitarity where the fermion-fermion scattering length diverges, we find that the loss rate is proportional to the 4/3 power of the fermionic density. This unusual exponent signals non-trivial two-body correlations in the system. Furthermore, we obtain a local measurement of the homogeneous contact at low temperature, in agreement with previous measurements based on thermodynamics and Bragg spectroscopy. Our results demonstrate that few-body losses can be used as a quantitative probe of quantum correlations in many-body ensembles. Specifically, it opens the possibility to measure quantitatively the Contact of the Unitary Fermi gas through the Normal-to-Superlfluid transition, where several theoretical models disagree.