Nonequilibrium pairing instability in ultracold Fermi gases with population imbalance

TL;DR

This paper investigates the nonequilibrium dynamics of spin-polarized ultracold Fermi gases after suddenly turning on pairing interactions, revealing how population imbalance affects pairing development, oscillation behavior, and temperature-dependent instabilities.

Contribution

The study provides new numerical and analytical insights into how population imbalance influences the time evolution and stability of pairing in ultracold Fermi gases.

Findings

Increased imbalance delays pairing development.

Higher imbalance lengthens oscillation periods and reduces maximum pairing amplitude.

A temperature-reentrant behavior of the initial instability exponent is observed.

Abstract

We present detailed numerical and analytical investigations of the nonequilibrium dynamics of spin-polarized ultracold Fermi gases following a sudden switching-on of the atom-atom pairing coupling strength. Within a time-dependent mean-field approach we show that on increasing the imbalance it takes longer for pairing to develop, the period of the nonlinear oscillations lengthens, and the maximum value of the pairing amplitude decreases. As expected, dynamical pairing is suppressed by the increase of the imbalance. Eventually, for a critical value of the imbalance the nonlinear oscillations do not even develop. Finally, we point out an interesting temperature-reentrant behavior of the exponent characterizing the initial instability.