Interaction energy and itinerant ferromagnetism in a strongly interacting Fermi gas in the absence of molecule formation

Understand

We investigate the interaction energy and the possibility of itinerant ferromagnetism in a strongly interacting Fermi gas at zero temperature in the absence of molecule formation.

• The interaction energy is obtained by summing the perturbative contributions of Galitskii-Feynman type to all orders in the gas parameter.
• It can be expressed by a simple phase space integral of an in-medium scattering phase shift.
• In both three and two dimensions (3D and 2D), the interaction energy shows a maximum before reaching the resonance from the Bose-Einstein condensate side, which provides a possible explanation of the experimental measurements of the interaction energy.