Xiaoke Li

A double species Na-23 and Rb-87 Bose-Einstein condensate with tunable miscibility via an interspecies Feshbach resonance

We have realized a dual-species Bose-Einstein condensate (BEC) of Na-23 and Rb-87 atoms and observed its immiscibility. Because of the favorable background intra-and inter-species scattering lengths, stable condensates can be obtained via efficient evaporative cooling and sympathetic cooling without the need for fine tuning of the interactions. Our system thus provides a clean platform for studying inter-species interactions-driven effects in superfluid mixtures. With a Feshbach resonance, we have successfully created double BECs with largely tunable inter-species interactions and studied the miscible-immiscible phase transition.

Formation of ultracold NaRb Feshbach molecules

We report the creation of ultracold bosonic

Coherent Heteronuclear Spin Dynamics in an Ultracold Spinor Mixture.

^{23}

Coherent spin mixing dynamics in thermal

Na

^{87}

^{87}

Rb spin-1 and spin-2 gases

Rb Feshbach molecules via magneto-association. By ramping the magnetic field across an interspecies Feshbach resonance, at least 4000 molecules can be produced out of the near degenerate ultracold mixture. Fast loss due to inelastic atom-molecule collisions is observed, which limits the pure molecule number, after residual atoms removal, to 1700. The pure molecule sample can live for 21.8(8) ms in the optical trap, long enough for future molecular spectroscopy studies toward coherently transferring to the singlet ro-vibrational ground state, where these molecules are stable against chemical reaction and have a permanent electric dipole moment of 3.3 Debye. We have also measured the Feshbach molecules binding energy near the Feshbach resonance by the oscillating magnetic field method and found these molecules have a large closed-channel fraction.

Long-range states of the NaRb molecule near the Na(3 S-2(1/2))+Rb(5 P-2(3/2)) asymptote

We report the observation of coherent heteronuclear spin dynamics driven by interspecies spin-spin interaction in an ultracold spinor mixture, which manifests as periodical and well-correlated spin oscillations between two atomic species. In particular, we investigate the magnetic field dependence of the oscillations and find a resonance behavior which depends on both the linear and quadratic Zeeman effects and the spin-dependent interaction. We also demonstrate a unique knob for controlling the spin dynamics in the spinor mixture with species-dependent vector light shifts.

A

We study the non-equilibrium coherent spin mixing dynamics in ferromagnetic spin-1 and antiferromagnetic spin-2 thermal gases of ultracold

^{23}

^{87}

Na and

Rb atoms. Long lasting spin population oscillations with magnetic field dependent resonances are observed in both cases. Our observations are well reproduced by Boltzmann equations of the Wigner distribution function. Compared to the equation of motion of spinor Bose-Einstein condensates, the only difference here is a factor of two increase in the spin-dependent interaction, which is confirmed directly in the spin-2 case by measuring the relation between the oscillation amplitude and the samples density.