Rotonlike Fulde-Ferrell Collective Excitations of an Imbalanced Fermi Gas in a Two-Dimensional Optical Lattice
Zlatko G. Koinov, Rafael Mendoza, Mauricio Fortes
We address the question of whether superfluidity can survive in the case of fermion pairing between different species with mismatched Fermi surfaces using as an example a population-imbalanced mixture of 6Li atomic Fermi gas loaded in a two-dimensional optical lattice at nonzero temperatures. The collective mode is calculated from the Bethe-Salpeter equations in the general random phase approximation assuming a Fulde-Ferrell order parameter. The numerical solution shows that, in addition to low-energy (Goldstone) mode, two rotonlike minima exist, and therefore, the superfluidity can survive in this imbalanced system.
Physical Review Letters•Mar 7, 2011•13 citations