Inhomogeneous Fermi mixtures at Unitarity: Bogoliubov-de Gennes vs. Landau-Ginzburg
(Dec 11, 2009)Abstract
We present an inhomogeneous theory for the low-temperature properties of a
resonantly interacting Fermi mixture in a trap that goes beyond the
local-density approximation. We compare the Bogoliubov-de Gennes and a
Landau-Ginzburg approach and conclude that the latter is more appropriate when
dealing with a first-order phase transition. Our approach incorporates the
state-of-the-art knowledge on the homogeneous mixture with a population
imbalance exactly and gives good agreement with the experimental density
profiles of Shin et al. Nature 451, 689 (2008). We calculate the
universal surface tension due to the observed interface between the
equal-density superfluid and the partially polarized normal state of the
mixture. We find that the exotic and gapless superfluid Sarma phase can be
stabilized at this interface, even when this phase is unstable in the bulk of
the gas.