The third virial coefficient of a two-component unitary Fermi gas across an Efimov-effect threshold
1 Institute for Advanced Study, Tsinghua University - Beijing, 100084, China
2 Laboratoire Kastler Brossel, ENS- PSL, CNRS, UPMC-Sorbonne Universités, Collège de France - Paris, France
Received: 30 October 2014
Accepted: 19 December 2014
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 $\alpha_c\simeq 13.6069$ 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 α across $\alpha_c$ since, unexpectedly, the three-body parameter characterizing the interaction is relevant even on the non-Efimovian side $\alpha<\alpha_c$ .
PACS: 67.85.-d – Ultracold gases, trapped gases
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