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

Chao Gao (1) , Shimpei Endo (2) , Yvan Castin (2)

1 Institute for Advanced Study [Tsinghua]
2 LKB (Lhomond) - Laboratoire Kastler Brossel

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 α across α_c ≃ 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 α across α_c since, unexpectedly, the three-body parameter characterizing the interaction is relevant even on the non-efimovian side α < α_c.

Mots clés: virial expansion; unitary gas; fermions; Efimov effect

Domaines: Gaz Quantiques [cond-mat.quant-gas]

Chao Gao, Shimpei Endo, Yvan Castin. The third virial coefficient of a two-component unitary Fermi gas across an Efimov-effect threshold. 2014. ⟨hal-01078973v1⟩