Production And Manipulation Of Ultracold Atoms

This dissertation presents an experimental study of the hydrodynamics expansion of a strongly interacting Fermi gas.A two component 6Li unitary Fermi gas of 5×106 atoms is created through a collisional Feshbach resonance centered near 834G,in a cigar-shaped optical dipole trap and we demonstrate that in the weak residual magnetic field curvature,the atom cloud undergoes an oscillatory quadrupole-like expansion over 30 ms.By analyzing the expansion dynamics according to the superfluid hydrodynamic equation,we derive several parameters characterizing quantum state of the trapped Fermionic superfluid,including the Bertsch parameter ? at unitarity and the effective polytropic index ? over the whole BEC-BCS crossover.The experimental estimate ?= 0.42(2)agrees well with the quantum Monte Carlo calculation 0.42(1),although it's a little larger than the high precision in-situ measurement 0.376(4).The values show a nonmonotonic behavior as a function of interaction strength,and reduce to the well-known theoretical results in the BEC,BCS and unitary limits.The modulation transfer spectroscopy of D1&D2 transitions of 6Li atoms in a vapor cell is also investigated in this study.The dependence of the modulation transfer spectra on probe beam intensity,driving frequency of EOM and polarizations of pump and probe beam is demonstrated.It was found that the crossover peak is more suitable for frequency stabilization of 6Li atoms.The magnetic field effect on the MTS signal is also studied which made it possible to enhance the MTS peak-to-peak signal specifically for D2 line.To show the significance of MTS over frequency modulation spectroscopy a detailed comparison is also presented.We also study the Bosonic Josephson junction dynamics of a Bose-Einstein condensate(BEC)in a deep double-well potential,where the tunneling between the two wells is modulated by another BEC trapped in a harmonic potential symmetrically positioned at the center of the double-well potential.The inter-species interactions couple the dynamics of the two BECs,which give rise to interesting features in the tunneling oscillations.Adopting a two-mode approximation for the BEC in the double-well potential and coupling it with the Gross-Pitaevskii equation of the harmonically trapped BEC,we numerically investigate the coupled dynamics of the BEC mixture and map out the phase diagram of the tunneling dynamics.Our results suggest the possibility of tuning the tunneling dynamics of BECs in double-well potentials.