Collective modes as a probe of imbalanced Fermi gases

We theoretically investigate the collective modes of imbalanced two-component one-dimensional Fermi gases with attractive interactions. This is done for trapped and untrapped systems both at zero and nonzero temperature, using self-consistent mean-field theory and the random phase approximation. We discuss how the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state can be detected and the periodicity of the associated density modulations determined from its collective mode spectrum. We also investigate the accuracy of the single-mode approximation for low-lying collective excitations in a trap by comparing frequencies obtained via sum rules with frequencies obtained from direct collective mode calculations. It is found that, for collective excitations where the atomic clouds of the two spin-species oscillate largely in phase, the single-mode approximation holds well for a large parameter regime. Finally, we investigate the collective mode spectrum obtained by parametric modulation of the coupling constant.