Competition between pairing and ferromagnetic instabilities in ultracold Fermi gases near Feshbach resonances

TL;DR

This paper investigates the early-time dynamics of ultracold Fermi gases near Feshbach resonances, focusing on the competition between ferromagnetic and pairing instabilities using an effective interaction model.

Contribution

It introduces an effective interaction model that incorporates Pauli blocking and energy dependence to analyze competing instabilities in ultracold Fermi gases.

Findings

Identifies the exponential growth rates of collective modes

Analyzes the conditions favoring ferromagnetic or pairing instabilities

Provides insights into the dynamical competition near Feshbach resonances

Abstract

We study the quench dynamics of a two-component ultracold Fermi gas from the weak into the strong interaction regime, where the short time dynamics are governed by the exponential growth rate of unstable collective modes. We obtain an effective interaction that takes into account both Pauli blocking and the energy dependence of the scattering amplitude near a Feshbach resonance. Using this interaction we analyze the competing instabilities towards Stoner ferromagnetism and pairing.