Conversion of an Atomic Fermi Gas to a Long-Lived Molecular Bose Gas

Abstract

We have converted an ultracold Fermi gas of 6Li atoms into an ultracold gas of 6Li2 molecules by adiabatic passage through a Feshbach resonance. Approximately 1.5 x 10(5) molecules in the least-bound, v=38, vibrational level of the X1Sigma(+)(g) singlet state are produced with an efficiency of 50%. The molecules remain confined in an optical trap for times of up to 1 s before we dissociate them by a reverse adiabatic sweep.

Fock-state dynamics in Raman photoassociation of Bose-Einstein condensates

“…Experimental efforts to form molecular condensates by photoassociation of atomic condensates have been at least partially successful, although the most successful method for the production of condensed molecules to date has been the recent combination of pairs of fermions using Feshbach techniques [13][14][15][16]. Because of Pauli blocking of the dissociation channel, the dynamics of this process, even if it were to be carried out using photoassociative techniques, are expected to be different from those of superchemistry [17].…”

Spectrum and Dynamics of the BCS-BEC Crossover from a Few-Body Perspective

“…In a recent experiment with optical lattices, the spectrum of two fermions in a trap has been measured [2], demonstrating that few body trapped systems can be studied in their own right. Also, the BCS-BEC crossover has been routinely explored in experiments with ultracold Fermi gases [4,5,6,7,8,9]. In this Letter, we explore the spectrum and dynamics of four trapped particles and we show how a few-body formulation allows us to obtain accurate solutions of the system without making the standard approximations of many-body theory.…”

“…[4] for 40 K. The fit of the experimental data to a Landau-Zener formula predicted a κ exp mol ≈ 62 ± 15. Also, experiments carried out at Rice measured the LandauZener parameter for 6 Li [7]. Taking into account the conditions of the experiment and the properties of the 6 Li Fano-Feshbach resonance at B ≈ 543.8G, we estimate κ exp mol ∼ 90.…”

“…By solving the problem from a few-body perspective, we are able to give accurate properties -especially energy levels as well as time-dependent dynamics -of the full quantum mechanical spectrum at zero temperature. As a result we achieve a deeper understanding of the global topology of the spectrum, in addition to making quantitative predictions of transition probabilities and dynamical properties of this system when interactions change with time as in experiments [4,5,6,7,8,9].To obtain the energy spectrum, we use a correlated gaussian basis set [10,11]. A diabatization procedure reduces the system to a tractable number of relevant eigenfunctions, after which we solve the time-dependent Schrödinger equation using the diabatic representation.…”

Universality in nonadiabatic behavior of classical actions in nonlinear models of Bose-Einstein condensates

“…The final state of the system contains the nonzero remnant fraction, which can be calculated as change in the classical action in the model (2), and scales as a power-law of the sweeping rate. The model was introduced in [26] in the attempt to describe recent experiments on Feshbach resonance passage [54,55,56,57], and some power laws were calculated there and compared with experimental data. For the case of nonzero initial molecular fraction, the power-law was also calculated in [27,28] according to the general theory.…”