Density response of a trapped Fermi gas: a crossover from the pair vibration mode to the Goldstone mode

TL;DR

This paper investigates how the density response of a trapped two-component Fermi gas transitions from pair vibration modes to Goldstone modes as interactions strengthen, revealing changes in collective excitation behavior.

Contribution

It introduces a combined Bogoliubov-deGennes and RPA approach to study collective excitations across interaction regimes in trapped Fermi gases, highlighting the crossover phenomenon.

Findings

Observation of a crossover from pair vibration to Goldstone mode

Depressed collective mode frequency with increased damping

Agreement with experimental density response data

Abstract

We consider the density response of a trapped two-component Fermi gas. Combining the Bogoliubov-deGennes method with the random phase approximation allows the study of both collective and single particle excitations. Calculating the density response across a wide range of interactions, we observe a crossover from a weakly interacting pair vibration mode to a strongly interacting Goldstone mode. The crossover is associated with a depressed collective mode frequency and an increased damping rate, in agreement with density response experiments performed in strongly interacting atomic gases.