Quantum Degenerate Fermi Gases of Ytterbium Atoms

Abstract

We performed evaporative cooling for dilute gases of ytterbium (Yb) isotopes in a crossed optical dipole trap and successfully cooled two fermionic and two bosonic species down to quantum degenerate regime, following the previous realization of Bose-Einstein condensation (BEC) in 174Yb. The elastic collision rate of fermionic 173Yb atoms with 6 spin components was found to be large enough to carry out efficient evaporation, which enables us to cool the atoms down to 0.6 T F , where T F is the Fermi temperature. In this regime, a plunge of evaporation efficiency was observed as an effect of the Fermi degeneracy. The other fermionic isotope 171Yb was cooled down to the temperature below T F by sympathetic cooling with bosonic 174Yb atoms. The sympathetic cooling technique has also been applied to 174Yb-176Yb Bose-Bose mixture. We have observed almost pure BEC of 174Yb and the bimodal distribution of 176Yb, showing the formation of BEC-BEC mixture. Moreover, we performed evaporative cooling of 170Yb atoms and realized the BEC.