Observation of collectivity enhanced magnetoassociation of ⁶Li in the quantum degenerate regime

Abstract

The association process of Feshbach molecules is well described by a Landau–Zener (LZ) transition above the Fermi temperature, such that two-body physics dominates the dynamics. However, using 6Li atoms and the associated Feshbach resonance at B r = 834.1 G, we observe an enhancement of the atom–molecule coupling as the fermionic atoms reach degeneracy, demonstrating the importance of many-body coherence not captured by the conventional LZ model. In the experiment, we apply a linear association ramp ranging from adiabatic to non-equilibrium molecule association for various temperatures. We develop a theoretical model that explains the temperature dependence of the atom–molecule coupling. Furthermore, we characterize this dependence experimentally and extract the atom–molecule coupling coefficient as a function of temperature, finding qualitative agreement between our model and experimental results. In addition, we simulate the dynamics of molecular association during a nonlinear field ramp. We find that, in the non-equilibrium regime, molecular association efficiency can be enhanced by sweeping the magnetic field cubically with time. Accurate measurement of the atom–molecule coupling coefficient is important for both theoretical and experimental studies of molecular association and many-body collective dynamics.

Optimized loading of ultracold Cs atoms in a magnetic levitated optical dipole trap

“…Far-off-resonance optical dipole trap is one of the most prevalent technologies for preparing and manipulating atoms and can provide the opportunity to investigate numerous physical including double potentials [12], microscopic traps [13,14], and optical lattices [15][16][17]. Optical dipole trap producing a near conservation well for atoms, is pivotal to the study of Bose-Einstein condensations [18,19], magnetically tunable Feshbach resonances [20,21], as well as formation of cold molecules [22,23]. Except for that, an optical dipole trap is typically utilized to trap and cool all spin states of the trapped atoms, which provides a favorable environment for studies of spinor condensates and multicomponent Fermi degenerate gas [24,25].…”