Dynamical properties of dipolar Fermi gases

TL;DR

This paper explores the dynamical behavior of dipolar Fermi gases, analyzing their stability, collective oscillations, and expansion dynamics, revealing how dipolar interactions influence these properties and lead to potential collapse.

Contribution

It introduces a variational approach to describe the energy and stability of dipolar Fermi gases, providing new insights into their collective modes and expansion behavior.

Findings

Identification of instability conditions near critical dipolar strength

Calculation of monopole and quadrupole mode frequencies showing softening

Demonstration of dipolar effects on expansion dynamics

Abstract

We investigate dynamical properties of a one-component Fermi gas with dipole-dipole interaction between particles. Using a variational function based on the Thomas-Fermi density distribution in phase space representation, the total energy is described by a function of deformation parameters in both real and momentum space. Various thermodynamic quantities of a uniform dipolar Fermi gas are derived, and then instability of this system is discussed. For a trapped dipolar Fermi gas, the collective oscillation frequencies are derived with the energy-weighted sum rule method. The frequencies for the monopole and quadrupole modes are calculated, and softening against collapse is shown as the dipolar strength approaches the critical value. Finally, we investigate the effects of the dipolar interaction on the expansion dynamics of the Fermi gas and show how the dipolar effects manifest in an expanded cloud.