BCS-BEC Crossover of Superfluid Fermions with Rabi Coupling

In this thesis we study the BCS-BEC crossover in a gas of ultracold atoms interacting via a two body contact potential and Rabi coupling. We start with a review of the standard BCS-BEC crossover and then derive the corresponding results for the Rabi-coupled system. Among the calculated quantities are the critical temperature, the energy gap, the condensate fraction, the superfluid fraction at the mean field level and the critical temperature beyond mean field, obtained with the NSR approach and the Babaev-Kleinert one.