Quantum-degenerate mixture of fermionic lithium and bosonic rubidium gases

TL;DR

This paper demonstrates the creation of a quantum-degenerate mixture of fermionic lithium and bosonic rubidium gases through sympathetic cooling, providing insights into interspecies interactions and collision dynamics.

Contribution

It reports the first observation of sympathetic cooling of fermionic lithium with bosonic rubidium leading to quantum-degenerate mixtures and estimates the interspecies scattering length.

Findings

Li and Rb gases reach quantum degeneracy.

Estimated interspecies s-wave scattering length |a_s|=20_{-6}^{+9} a_B.

Residual Rb atoms cause inelastic collision losses.

Abstract

We report on the observation of sympathetic cooling of a cloud of fermionic 6-Li atoms which are thermally coupled to evaporatively cooled bosonic 87-Rb. Using this technique we obtain a mixture of quantum-degenerate gases, where the Rb cloud is colder than the critical temperature for Bose-Einstein condensation and the Li cloud colder than the Fermi temperature. From measurements of the thermalization velocity we estimate the interspecies s-wave triplet scattering length |a_s|=20_{-6}^{+9} a_B. We found that the presence of residual rubidium atoms in the |2,1> and the |1,-1> Zeeman substates gives rise to important losses due to inelastic collisions.