A Bose-Einstein condensate immersed in a Fermi sea: observation of ultra-cold mixture of Bose and Fermi gases

We report the formation of mixtures of bosonic and fermionic quantum systems in dilute atomic gases. Two isotopes of lithium are cooled by standard laser cooling techniques and transferred into a magnetic trap. Evaporative cooling is performed selectively on the bosonic isotope (Li-7), while its fermionic counterpart (Li-6) is cooled sympathetically until simultaneous quantum degeneracy is reached. The Li-7 Bose Einstein condensate contains a very small fraction of thermal atoms and is in thermal equilibrium with Li-6 Fermi sea at a temperature of (1)/(5) of the Fermi temperature. (C) 2003 Elsevier Science B.V. All rights reserved.