Phase Transition in Asymmetrical Superfluids

In this paper we study phase transition in asymmetrical fermion superfluids. In this scenario the candidates to form pair are particles with mismatched masses and Fermi surfaces. We derive expressions for the determination of the critical temperature in relevant situations for fermionic atom experiments. We argue that an asymmetrical fermion superfluid always undergoes a first order phase transition to the normal phase as a function of the increasing mass and (or) chemical potential asymmetry, except if the constraint $m_a \mu_a=m_b \mu_b$ is imposed.