Fermi gas

For many years rubidium has been a workhorse in the investigation of ultracold atoms.  Now JQI scientists are using Rb to cool another species, ytterbium, an element prized for its possible use in advanced optical clocks and in studying basic quantum phenomena.   Yb shows itself useful in another way: it comes in numerous available isotopes, some of which are bosonic in nature and some fermionic.
Yb-171 has proven satisfactorily amenable to cooling in the atom trap lab of Steve Rolston and Trey Porto.  First Rb-87 atoms are loaded into a magneto-optic trap---an enclosure where magnetic fields and laser beams are used to confine atoms---and then cooled until they form a Bose-Einstein condensate (BEC).  Slow-moving Yb atoms, in contact with the Rb atoms, are cooled right along with them.  Thus Yb atoms lose excess energy to warming the colder Rb atoms.