title: Breakdown of universality for unequal-mass Fermi gases with infinite scattering length.
abstract: We treat small trapped unequal-mass two-component Fermi gases at unitarity within a nonperturbative microscopic framework and investigate the system properties as functions of the mass ratio κ, and the numbers N1 and N2 of heavy and light fermions. While equal-mass Fermi gases with infinitely large interspecies s-wave scattering length a(s) are universal, we find that unequal-mass Fermi gases are, for sufficiently large κ and in the regime where Efimov physics is absent, not universal. In particular, the (N₁,N₂) = (2, 1) and (3, 1) systems exhibit three-body and four-body resonances at κ=12.314(2) and 10.4(2), respectively, as well as surprisingly large finite-range effects. These findings have profound implications for ongoing experimental efforts and quantum simulation proposals that utilize unequal-mass atomic Fermi gases.
authors.affiliation: Department of Physics and Astronomy, Washington State University, Pullman, 99164-2814, USA.
authors.forename: D
authors.initials: D
authors.lastname: Blume
authors.forename: K M
authors.initials: KM
authors.lastname: Daily