ATOMIC PHYSICS SEMINAR

Scott Papp
JILA/University of Colorado

Tuesday, December 19, 2006
2:00 pm in SPL 52

Tunable interactions in ultracold Bose gases: New experiments with ⁸⁵Rb and ⁸⁷Rb

Abstract: Many experiments have been performed recently using tunable interactions in ultracold atomic gases. At JILA the ability to tune the scattering length of a ⁸⁵Rb BEC was used to cause the controlled collapse of a condensate as well as to create a coherent atom-molecule superposition. These experiments prompted the need for a new apparatus to continue studies of BEC with tunable interactions. I will present the results of several recent experiments with an ultracold mixture of ⁸⁵Rb and ⁸⁷Rb in which we tune not only the ⁸⁵Rb scattering length but also the interaction between ⁸⁵Rb and ⁸⁷Rb using Feshbach resonances. These include the creation of heteronuclear Feshbach molecules and the observation of phase separation in a dual BEC. Since ⁸⁵Rb is difficult to evaporatively cool, we took a new approach to ⁸⁵Rb BEC; we sympathetically cool ⁸⁵Rb with ⁸⁷Rb in both magnetic and optical traps. With this new system we are able to produce ⁸⁵Rb BEC with 80,000 atoms, a factor of five improvement over the previous apparatus, and we also can study a dual BEC of both Rb species.