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arXiv · 2102.01805

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

Vineetha Naniyil·Yijia Zhou·Guy Simmonds·Nathan Cooper·Weibin Li·Lucia Hackermüller
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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.

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Vineetha Naniyil, Yijia Zhou, Guy Simmonds, Nathan Cooper, Weibin Li, Lucia Hackermüller. 2021-02-03. Observation of collectivity enhanced magnetoassociation of $^6$Li in the quantum degenerate regime. https://doi.org/10.1088/1367-2630/ac9b81

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