1202.3348 (E. Fratini et al.)

Mass imbalance effect in resonant Bose-Fermi mixtures    [PDF]

E. Fratini, P. Pieri

We consider a homogeneous Bose-Fermi mixture, with the boson-fermion
interaction tuned by a Fano-Feshbach resonance, in the presence of mass and
density imbalance between the two species. We first study the finite
temperature phase diagram for the specific case of the mass-imbalanced mixture
87Rb-40K for different values of the density imbalance. We then analyse the
quantum phase transition associated with the disappearance at zero temperature
of the boson condensate above a critical boson-fermion coupling. We find a
pronounced dependence of the critical coupling on the mass ratio and a weak
dependence on the density imbalance. For a vanishingly small boson density, we
derive the asymptotic expressions for the critical coupling in the limits of
small and large mass ratios. These expressions are relevant also for the
polaron-molecule transition in a Fermi mixture at small and large mass ratios.
The analysis of the momentum distribution functions at sufficiently large
density imbalances shows an interesting effect in the bosonic momentum
distribution due to the simultaneous presence of composite fermions and
unpaired fermions.

View original: http://arxiv.org/abs/1202.3348