Density, spin, and pairing instabilities in polarized ultracold Fermi gases

Abstract

We study the influence of population imbalance on the pairing, spin, and density instabilities of a two component ideal Fermi gas after a sudden quench of interactions near a Feshbach resonance. Over a large region of parameters the pairing instability is dominated by finite momentum pairing, suggesting the possibility of observing FFLO-like states in the unstable initial dynamics. Long-wavelength density instabilities are found on the BCS side of the resonance, and are interpreted as a precursor of the phase separation expected at equilibrium. On the BEC side of the resonance, the pairing instability is present for scattering lengths that are larger than a critical value that is only weakly dependent on population imbalance and always smaller than the scattering length at which the Stoner-like spin instability occurs.

8 pages, 5 figures

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• Polarons, Dressed Molecules, and Itinerant Ferromagnetism in ultracold Fermi gases
• Observation of quantum-limited spin transport in strongly interacting two-dimensional Fermi gases
• Observation of the Leggett-Rice effect in a unitary Fermi gas
• Itinerant Ferromagnetism in a polarized two-component Fermi gas
• Time-resolved observation of competing attractive and repulsive short-range correlations in strongly interacting Fermi gases
• Nonperturbative Effects on the Ferromagnetic Transition in Repulsive Fermi Gases
• Quantum Monte Carlo simulations of two-dimensional repulsive Fermi gases with population imbalance
• Interaction energy and itinerant ferromagnetism in a strongly interacting Fermi gas in the absence of molecule formation
• Finite range and upper branch effects on itinerant ferromagnetism in repulsive Fermi gases: Bethe-Goldstone ladder resummation approach
• Non-Hermitian Ferromagnetism in an Ultracold Fermi Gas
• Lifshitz tricritical point and its relation to the FFLO superconducting state
• Itinerant ferromagnetism of a dipolar Fermi gas with Raman-induced spin-orbit coupling
• Contact potential instability in the path-integral description of itinerant ferromagnetism