In spin- and mass-imbalanced Fermi superfluids, Anderson-Bogolyubov sound modes acquire Landau damping at zero temperature once the Fermi-surface mismatch exceeds a threshold set by the mass ratio and the superfluid gap.
Leggett collective excitations in a two-band Fermi superfluid at finite temperatures
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abstract
The Leggett collective excitations for a two-band Fermi gas with s-wave pairing and Josephson interband coupling in the BCS-BEC crossover at finite temperatures are investigated within the Gaussian pair fluctuation approach. Eigenfrequencies and damping factors for Leggett modes are determined in a nonperturbative way, using the analytic continuation of the fluctuation propagator through a branch cut in the complex frequency plane, as in Phys. Rev. Lett. 122, 093403 (2019). The treatment is performed beyond the low-energy expansion, which is necessary when the collective excitation energy reaches the pair-breaking continuum edge. The results are applied in particular to cold atomic gases at the orbital Feshbach resonance and in a regime far from BEC, which can be relevant for future experiments.
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cond-mat.quant-gas 1years
2019 1verdicts
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Damping of the Anderson-Bogolyubov mode by spin and mass imbalance in Fermi mixtures
In spin- and mass-imbalanced Fermi superfluids, Anderson-Bogolyubov sound modes acquire Landau damping at zero temperature once the Fermi-surface mismatch exceeds a threshold set by the mass ratio and the superfluid gap.