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On the conversion efficiency of ultracold fermionic atoms to bosonic molecules via Feshbach resonances

E. Pazy·A. Vardi·Y. B. Band
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Abstract

We explain why the experimental efficiency observed in the conversion of ultracold Fermi gases of $^{40}$K and $^{6}$Li atoms into diatomic Bose gases is limited to 0.5 when the Feshbach resonance sweep rate is sufficiently slow to pass adiabatically through the Landau Zener transition but faster than ``the collision rate'' in the gas, and increases beyond 0.5 when it is slower. The 0.5 efficiency limit is due to the preparation of a statistical mixture of two spin-states, required to enable s-wave scattering. By constructing the many-body state of the system we show that this preparation yields a mixture of even and odd parity pair-states, where only even parity can produce molecules. The odd parity spin-symmetric states must decorrelate before the constituent atoms can further Feshbach scatter thereby increasing the conversion efficiency; ``the collision rate'' is the pair decorrelation rate.

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E. Pazy, A. Vardi, Y. B. Band. 2004-08-12. On the conversion efficiency of ultracold fermionic atoms to bosonic molecules via Feshbach resonances. https://doi.org/10.1103/physrevlett.93.120409

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