Collective Atomic Recoil Motion And Feshbach Resonances In Ultracold Fermi-Bose Mixtures

In this thesis, the experiment allowing for the creation of large mixtures of quantum degerate fermionic 40K and bosonic 87Rb are firstly presented. The design, construction and the apparatus are briefly described here. More detailsfocus to the designs of three coils for the QUIC trap. At low temperature, both the Bose and Fermi gases are expanded relative to a classical gas at the same temperature. For fermions, however, this effect is due to the Pauli exclusion principle rather than atom-atom interactions. While in Bose case a phase transition separates the degenerate and classical regime, a trapped Fermi gas undergoes a gradual crossover between the classical limit and the compact Fermi sea.We have transport horizontally lot of ultracold atoms over a distance of 12mm in a harmonic trap. By using a horizontal homogeneous magnetic field in the direction reverse to the QUIC trap to decrease the bias field, we achieve a enough radial frequency providing strong confinement in order to hold the atoms against gravity for the whole transport distance. We demonstrate suppression in the oscillation of the atomic clouds using a technique based on the interaction between the atom and the homogeneous magnetic field in the final transport. This transport technique avoids the heating and loss induced by the mechanical noise and might have applications in transporting larger distances with quantum degenerate mixed gases.We demonstrate clear collective atomic recoil motion in a dilute, momentum-squeezed, ultra-cold degenerate fermion gas by circumventing the effects of Pauli blocking. Although gain from bosonic stimulation is necessarily absent because the quantum gas obeys Fermi-Dirac statistics, collective atomic recoil motion from the underlying wave-mixing process is clearly visible. With a single pump pulse of the proper polarization, we observe two mutually-perpendicular wave-mixing processes occurring simultaneously. Our experiments also indicate that the red-blue pump detuning asymmetry observed with Bose-Einstein condensates does not occur with fermions.Homonuclear and heteronuclear Feshbach resonances have been used in order to change the interaction properties of the mixture in a controlled fashion. We report the experimental preparation of the absolute ground states by means of the radio-frequency and microwave adiabatic rapid passages and the observation of magnetic Feshbach resonances in the ultracold mixture between 0 and 600 G, including 6 homonuclear and 4 heteronuclear Feshbach resonances. The resonances are identified by the abrupt trap loss of atoms induced by the strong inelastic three-body collisions. These Feshbach resonances should enable experimental control of the interspecies interactions.