title: Rotonlike Fulde-Ferrell collective excitations of an imbalanced Fermi gas in a two-dimensional optical lattice.
abstract: 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.
authors.affiliation: Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas 78249, USA. Zlatko.Koinov@utsa.edu
authors.forename: Zlatko
authors.initials: Z
authors.lastname: Koinov
authors.forename: Rafael
authors.initials: R
authors.lastname: Mendoza
authors.forename: Mauricio
authors.initials: M
authors.lastname: Fortes