# The third virial coefficient of a two-component unitary Fermi gas across an Efimov-effect threshold

Abstract : We consider a mixture of two single-spin-state fermions with an interaction of negligible range and infinite $s$-wave scattering length. By varying the mass ratio $\alpha$ across $\alpha_c\simeq 13.6069$ one can switch on-and-off the Efimov effect. We determine analytically the third cluster coefficient of the gas. We show that it is a smooth function of $\alpha$ across $\alpha_c$ since, unexpectedly, the three-body parameter characterizing the interaction is relevant even on the non-Efimovian side $\alpha<\alpha_c$.
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https://hal.archives-ouvertes.fr/hal-01078973
Contributor : Yvan Castin <>
Submitted on : Friday, April 10, 2015 - 10:09:38 AM
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Chao Gao, Shimpei Endo, Yvan Castin. The third virial coefficient of a two-component unitary Fermi gas across an Efimov-effect threshold. EPL - Europhysics Letters, European Physical Society/EDP Sciences/Società Italiana di Fisica/IOP Publishing, 2015, 109, pp.16003. ⟨10.1209/0295-5075/109/16003⟩. ⟨hal-01078973v3⟩

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