Beliaev damping of the Goldstone mode in atomic Fermi superfluids

Abstract

Beliaev damping in a superfluid is the decay of a collective excitation into two lower frequency collective excitations; it represents the only decay mode for a bosonic collective excitation in a superfluid at T = 0. The standard treatment for this decay assumes a linear spectrum, which in turn implies that the final state momenta must be collinear to the initial state. We extend this treatment, showing that the inclusion of a gradient term in the Hamiltonian yields a realistic spectrum for the bosonic excitations; we then derive a formula for the decay rate of such excitations, and show that even moderate nonlinearities in the spectrum can yield substantial deviations from the standard result. We apply our result to an attractive Fermi gas in the BCS-BEC crossover: here the low-energy bosonic collective excitations are density oscillations driven by the phase of the pairing order field. These collective excitations, which are gapless modes as a consequence of the Goldstone mechanism, have a spectrum which is well established both theoretically and experimentally, and whose linewidth, we show, is determined at low temperatures by the Beliaev decay mechanism.

arXiv comment8 pages, 3 figures

References in corpus (13)

• Observation of resonance condensation of fermionic atom pairs
• The Unitary Fermi Gas: From Monte Carlo to Density Functionals
• Quantum Fluctuations in the Superfluid State of the BCS-BEC Crossover
• Collective mode of homogeneous superfluid Fermi gases in the BEC-BCS crossover
• Bulk and Collective Properties of a Dilute Fermi Gas in the BCS-BEC Crossover
• Pairing fluctuations and the superfluid density through the BCS-BEC crossover
• Extended Thomas-Fermi Density Functional for the Unitary Fermi Gas
• Beliaev damping of quasi-particles in a Bose-Einstein condensate
• The experimental observation of Beliaev damping in a Bose condensed gas
• Pseudogap and preformed pairs in the imbalanced Fermi gas in two dimensions
• Pair excitations and parameters of state of imbalanced Fermi gases at finite temperatures
• Decay of Bogoliubov quasiparticles in a nonideal one-dimensional Bose gas
• Collective modes in asymmetric ultracold Fermi systems

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• Vortices and antivortices in two-dimensional ultracold Fermi gases
• Propagation of first and second sound in a two-dimensional Fermi superfluid
• Quantum kinetics of quenched two-dimensional Bose superfluids
• Landau-Khalatnikov phonon damping in strongly interacting Fermi gases
• Tuning Dissipation and Excitations in Superfluid Fermi Gases with a Moving Impurity
• Unitary Fermi superfluid near the critical temperature: thermodynamics and sound modes from elementary excitations
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