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Leggett collective excitations in a two-band Fermi superfluid at finite temperatures

Journal Contribution - e-publication

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 Kurkjian et al (2019 Phys. Rev. Lett. 122 093403). 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.
Journal: New journal of physics
ISSN: 1367-2630
Volume: 21
Publication year:2019
Keywords:A1 Journal article
BOF-keylabel:yes
BOF-publication weight:3
Authors:International
Authors from:Higher Education
Accessibility:Open