Observation of collectivity enhanced magnetoassociation of ${}^6$Li 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 ${}^6$Li 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.

18 pages, 6 figures

References in corpus (16)

• Collective excitations of a degenerate gas at the BEC-BCS crossover
• Enhanced sensitivity to variation of the fine structure constant and m_p/m_e in diatomic molecules
• Collisions of ultracold ^{23}Na^{87}Rb molecules with controlled chemical reactivities
• Adiabatic association of ultracold molecules via magnetic field tunable interactions
• Non-adiabacity and large flucutations in a many particle Landau Zener problem
• Focus on Shortcuts to Adiabaticity
• Many-body effects on adiabatic passage through Feshbach resonances
• Kibble-Zurek scaling in quantum speed limits for shortcuts to adiabaticity
• Many-Body Effects on Nonadiabatic Feshbach Conversion in Bosonic Systems
• Production efficiency of Feshbach molecules in fermion systems
• Collective Dissipative Molecule Formation in a Cavity
• Role of Particle Interactions in the Feshbach Conversion of Fermion Atoms to Bosonic Molecules
• Molecular production at a wide Feshbach resonance in Fermi-gas of cooled atoms
• Pair formation in quenched unitary Bose gases
• Versatile Cold Atom Source for Multi-Species Experiments
• Decay and revival of a transient trapped Fermi condensate

Cited by in corpus (2)

• Parametric tuning of quantum phase transitions in ultracold reactions
• Adaptive, symmetry-informed Bayesian metrology for precise quantum technology measurements