Effective theory of excitations in a Feshbach resonant superfluid

Abstract

A strongly interacting Fermi gas, such as that of cold atoms operative near a Feshbach resonance, is difficult to study by perturbative many-body theory to go beyond mean field approximation. Here I develop an effective field theory for the resonant superfluid based on broken symmetry. The theory retains both fermionic quasiparticles and superfluid phonons, the interaction between them being derived non-perturbatively. The theory converges and can be improved order by order, in a manner governed by a low energy expansion rather than by coupling constant. I apply the effective theory to calculate the specific heat and propose a mechanism of understanding the empirical power law of energy versus temperature recently measured in a heat capacity experiment.

4+ pages, 1 figure; Added references, corrected and clarified minor statements (v.2)

References in corpus (2)

• Collective excitations of a degenerate gas at the BEC-BCS crossover
• Collective modes and ballistic expansion of a Fermi gas in the BCS-BEC crossover

Cited by in corpus (6)

• Many-Body Physics with Ultracold Gases
• Superfluidity in a Three-flavor Fermi Gas with SU(3) Symmetry
• Finite temperature damping of collective modes of a BCS-BEC crossover superfluid
• Effective theory for the Goldstone field in the BCS-BEC crossover at T=0
• Unconventional interaction between vortices in a polarized Fermi gas
• Anderson-Bogoliubov collective excitations in superfluid Fermi gases at nonzero temperatures