  In this Letter we map out the mean field energy potential landscape of
fermion pairing states with population imbalance near broad Feshbach
Resonances. We apply the landscape to investigate the nature of phase
separation, when the Hilbert space is subject to the constraint of constant
population imbalance. We calculate the scattering length dependence of the
critical population imbalance for various phase separated states across
Feshbach resonances.
