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 $\alpha$ 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 $\alpha<\alpha_c$.

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

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. EPL - Europhysics Letters, 2015, 109, pp.16003. ⟨10.1209/0295-5075/109/16003⟩. ⟨hal-01078973v3⟩